BASIC EPIDEMIOLOGICAL CONCEPTS. RESERVOIRS AND SOURCES OF INFECTIOUS AGENTS. MECHANISMS, FACTORS AND WAYS TRANSMISSION OF INFECTIOUS AGENTS.

RODENT CONTROL. DEZINSEKTION. DISINFECTION AND STERILIZATION.

ORGANIZATION AND CONDUCT IMMUNIZATION. PREPARATIONS FOR THE CREATION OF ACTIVE AND PASSIVE IMMUNITY. ROUTINE VACCINATIONS AND EPIDEMIC INDICATIONS.

 

General Epidemiology

The Subject Matter of Epidemiology

http://intranet.tdmu.edu.ua/www/tables/1781.jpg

http://intranet.tdmu.edu.ua/www/tables/2061.jpg

The word “epidemiology” has been used since the time when most of the infectious diseases were epidemic. Today, when infectious morbidity has considerably decreased, the concept of epidemiology includes the study of objective laws of aetiology, distribution and control of infectious diseases in a human community, and also elaboration of methods to prevent and control these diseases.

The following definition of the term “epidemiology” was formulated at the International Symposium of Epidemiologists in Prague (I960):

http://www.jblearning.com/samples/0763728799/28799_CH02_023_060.pdf

http://www.authorstream.com/Presentation/ashokk_kapu-85122-general-epidemiology-ashok-epid-new-entertainment-ppt-powerpoint/

http://www.slideshare.net/akhileshbhargava/general-epidemiology-3044373

Epidemiology is an independent branch of medicine studying aetiology and spreading of infectious diseases in a human community and is aimed at prevention, control, and final eradication of these diseases”.

General and special epidemiologies are distinguished. General epidemiology studies the laws of distribution of infectious diseases among people (characteristics of sources of infection, the mechanism of transmission, susceptibility to infection, and the like) and the general principles of prevention and control of these diseases. Special epidemiology studies epidemiologic characteristics of each particular infectious disease and the methods to prevent and control it.

History of epidemiology. Ancient people had their own concept of contagiosity of some diseases and took first prophylactic measures; they rejected people with infectious diseases from their community, used variolation (deliberate inoculation with smallpox virus), disinfection, etc. All these measures were empirical and their efficacy was low. At those times it was impossible to prove instrumentally that infectious diseases might be evoked by living microorganisms, but numerous epidemics of black plague, smallpox and typhus, especially in the 14-15th centuries, aroused such suspicions in physicians. Fracastorius (Pic. 1), an Italian physician (1483-1553), produced a theory that proved contagiosity of these diseases.

Pic. 1. D. Fracastorius (1478-1553).

In Russia of the llth century, they isolated people with contagious diseases and burned the dead separately from the others. First quarantines were organized in the 16th century: patients were separated from their relatives, and funeral services over the dead were forbidden.

To prevent spread of plague epidemic into Moscow in 1552, posts were first organized in Russia to prevent penetration of people into the city from the outside. In the 17th century, quarantine piquets were organized during epidemics out at the entrance to the city and at the houses with the diseased. When a family died, the house with the dead and the utensils was bumed. According to the law, any case suspected for a contagious disease had to be reported to the officials.

In the 18th century, Edward Jenner (Pic. 2) an English physician, (1749-1823) devised a safe and effective method to prevent natural smallpox by inoculating people with cowpox vaccine.

At about the same time, the Russian epidemiologist D. Samoilovich (1744-1805) (Pic. 3) was among the first who attempted to discover microscopically the causative factor of plague in excrements and various tissues of the diseased. He was also actively involved in control of plague in Moscow in 1771-1772. Samoilovich organized quarantines at the Black Sea coastal area and became world famous for his work in epidemiology.

   Pic. 2. E. Jenner.                                   Pic. 3. D. Samoilovich

 

Development of industry and trade between different countries stimulated advances in medicine, including sanitary, quarantine, and anti-epidemic services.

The second half of the 19th century was marked by vigorous development of physics (optics), chemistry, biology and other sciences, which all provided conditions for developing a new science-microbiology.

The scientific discoveries made by Pasteur, Mechnikov, Koch, Ivanovsky and many others promoted the study of aetiology, pathogenesis, course of infectious disease and also their epidemiology. The study of epidemiology of some infectious diseases and working out of prophylactic measures revealed the important role of social factors in the spread of epidemics. Inadequate labour and living conditions, poverty, and poor sanitation promoted the spread of contagious diseases.

A great contribution to epidemiology was made by Minch 11 (1836-1896) and Mochutkovsky (1845-1903), who inoculated themselves with the blood of patients with recurrent fever (Minch) and typhoid fever (Mochutkovsky). They proved by their experiments that the diseases could be transmitted by blood-sucking insects.

Gabrichevsky (1860-1907) made an important contribution to the study of diphtheria (serotherapy), scarlet fever (study of aetiology, manufacture of vaccines and vaccination), epidemiology of malaria, etc.

Zabolotny (1866-1929) is the founder of Ukrainian epidemiology. He is the author of numerous papers on epidemiology of plague, cholera, epidemic typhus, etc. and also of the manual entitled “Fundamentals of Epidemiology”. Gromashevsky continued studies of their teacher.

Sysin (1879-1956), Semashko (1874-1949), Soloviev (1879-1928), Bashenin (1882-1978) and Martsinovsky (1874-1934) worked much to create anti-epidemic service in the Soviet state. Further development of the theory of epidemiology is associated with the names of Pavlovsky (1884-1965) and Gromashevsky (1887-1980) (Pic. 4). Pavlovsky’s works in the field of parasitology have won world repute. He developed also the theory of natural nidality of some infectious diseases.

Soviet epidemiologists Zabolotny, Vogralik, Bashenin, Gromashevsky, Pavlovsky and others have developed several theories in epidemiology. These are the first and second laws of sources of infection and the teaching of epidemic process. According to the law of infectious source, any infected person can be the source of infection; sometimes, this can be an animal. According to the second law, there exists agreement between location of the causative microorganism in a macroorganism and the mechanism of infection transmission. This law was used by Gromashevsky for classification of infectious diseases. The theory of epidemic process postulates that such a process develops and is maintained only through the interaction between the source of infection, the specific mechanism of transmission, and susceptibility of population with respect to a given disease. Teaching of natural nidality of infectious diseases and the effect of social factor on the course of an epidemic process are very important for a successful control of infectious diseases as well.

 

 

 

 

 

 

 

Pic. 4. Gromashevsky (1887-1980)

 

Advances in epidemiology are infeasible without improvement of labour and living conditions, adequate health care, and planned anti-epidemic measures.

http://ressources.ciheam.org/om/pdf/b25/99600239.pdf

http://www.jblearning.com/samples/0763728799/28799_CH02_023_060.pdf

 

The Concept of Infection

An infectious process is the interaction of a pathogenic microorganism with a macroorganism under certain environmental and social conditions. The concept “infectious disease” means the condition manifested by a disease state of a patient and the so-called carrier state.

The specific properties of infective agents, various pathogenicity and virulence of these agents, as well as the quantity of microorganisms that enter the macroorganism, resistance of the macroorganism and duration of specific immunity account for the multitude of clinical manifestations of infection.

Infection can be clinically pronounced or it may be asymptomatic, which is known as the carrier state (parasite, bacterium, virus carrier state). A clinically manifest infection can run a typical or atypical course. Patients with a typical form of infection demonstrate all symptoms specific for a given disease. One or several symptoms of a given disease are absent from the clinical picture of an atypical form, or the symptoms can be modified. A disease can be acute or run a protracted or even a chronic course.

A clinically manifest disease is usually classed as mild, moderate, and severe; according to the duration, the disease can be acute or chronic.

An acute infection (smallpox, measles, plague) is characterized by a short stay of the causative agent in the body and development of specific immunity in the patient toward the given infection.

A chronic infection (brucellosis, tuberculosis) can last for years.

Asymptomatic infections can be subclinical and latent.

A person with a subclinical infection (acute and chronic) looks in full health, and the disease can only be diagnosed by detecting the causative agents, specific antibodies, and functional and morphological changes in the organs and tissues that are specific for a given disease. Such patients (or carriers) are a special danger for the surrounding people since they are the source of infection. At the same time, a repeated subclinical infection in poliomyelitis, diphtheria, influenza, and some other acute infections promotes formation of an immune group of people (herd immunity). Acute and chronic subclinical forms (carrier state) are more common in typhoid fever, paratyphoid B, salmonellosis, viral hepatitis B, etc.

Latent or persistent forms of human and animal infections are a prolonged asymptomatic interaction of macroorganisms with the pathogenic agents which are present in modified (“defective”) forms. These are defective interfering particles in latent viral infections, and L forms, spheroplasts, etc. in bacterial infections. Being inside the host cell, these forms survive for long periods of time and are not released into the environment. Under the action of various provoking factors (such as thermal effects, injuries, psychic trauma, transplantation, blood transfusion, various disease states), persistent infection can be activated and become clinically manifest. The microbe regains its pathogenic properties.

Persistence of virus has been studied best of all, but at the present time, persistence of other pathogenic factors has been intensively studied as well, e. g. of the L forms of streptococci, staphylococci, meningococci, cholera vibrio, typhoid fever bacilli, microbes causing diphtheria, tetanus, etc.

Protozoa and rickettsia can also persist. For example, latent epidemic recrudescent typhus infection is manifested by relapses of epidemic recrudescent typhus (Brill’s disease).

The Concept of Epidemic Process

http://stat.fsu.edu/techreports/M454.pdf

Microorganisms causing infectious diseases parasitize on host and persist due to continuous reproduction of new generations which change their properties in accordance with evolution of the environment conditions. Living inside its host, the microorganism persists for a definite period of time. Then the pathogenic microorganism can survive by changing its residence, i.e., by moving to another host via a corresponding transmission mechanism. This continuous chain of successive transmission of infection (patient-carrier), manifested by symptomatic or asymptomatic forms of the disease, is called an epidemic process.

According to Gromashevsky, the source of infectious microorganisms is an object which is the site of natural habitation and multiplication of the pathogenic microorganisms, and  in which the microorganisms are accumulared. Since pathogenic nucroorgansms are parasites, only living macroorganism can be such an object, i.e., a human or an animal.

An epidemic focus is the residence of infection source including the surrounding territory within the boundaries of which, the source can, under given conditions, transmit a given disease through the agency of the pathogenic microorganisms. The focus of infection remains active until the pathogenic microorganisms are completely eradicated, plus the maximal incubation period in persons that were in contact with the source of infection. The following three obligatory factors are necessary for the onset and continuous course of an epidemic process: the source of pathogenic microorganism, the mechanism of their transmission, and macroorganisms susceptible to infection (Pic. 5).

Pic. 5. Three obligatory factors are necessary for the onset and continuous course of an epidemic process: 1. the source of pathogenic microorganism, 2. the mechanism of their transmission, and 3. macroorganisms susceptible to infection

Infectious diseases are classed according to their source as anthroponoses (the source of infection is man), zoonoses (the source of infection is animal), and anthropozoonoses (both man and animal can be the source of infection).

An infected macroorganism (man or animal), being the sole source of infection, can have either clinically manifest or asymptomatic form of the disease.

A diseased person is the primary source from which the infection spreads. A patient is the most dangerous source of infection because he or she releases a great quantity of the pathogenic microorganisms.

The danger of infection spreading from the patient depends on the period of the disease. During the incubation period the role of the patient is not great because the pathogenic microorganism resides inside tissues and is seldom released from the infected organism. The pathogenic agents are released into environment during the late incubation period only in measles, cholera, dysentery, and some other diseases. The greatest quantity of microbes are released during the advanced stage of the disease which is associated with some clinical manifestations of the disease such as frequent stools (dysentery), frequent stools and vomiting (cholera), sneezing and cough (airway infections). The danger of infection spreading during the early period of the disease depends on pathogenesis of a particular infectious disease. For example, in typhoid fever or paratyphoid A and B, the patients are not dangerous to the surrounding people during the first week of the disease, while in respiratory infections, the patient is a danger to the surrounding people from the moment when the clinical symptoms of the disease become apparent.

Severity of the disease is of great epidemiologic importance for determining “the source of infection”. If the disease is severe, the patient remains in bed and can only infect his relatives. But it is difficult to diagnose the disease if it runs a mild course; besides, the patient often does not attend for medical aid and continues performing his routine duties (at the office, school, and the like) thus actively promoting the spread of infection.

Carrier of infection is another source of morbidity. According to modern views, carrier state is an infectious process that runs an asymptomatic course. But those who sustained an infectious disease, convalescents, and also healthy persons (transition) can also be carriers of infectious microorganisms. True, carriers release pathogenic agents into the environment in a smaller quantity than patients with clinically manifest diseases, but they are danger to community too since they actively associate with healthy people and spread the infection.

Recovery from some infectious diseases, e.g. dysentery, typhoid fever, paratyphoid, diphtheria, meningococcal infection, viral hepatitis B, is not always attended by complete destruction of the microbes in the patient. Carrier state can persist in persons who sustained diphtheria or meningococcal infection after their clinical recovery: acute carrier state can last from several days to several weeks. Persons who sustained typhoid fever or paratyphoid B can be the source of spread of the pathogenic microorganisms for months. Carrier state can persist for years or even for the rest of life (chronic carrier state) in 3-5 per cent of cases, which can be explained by defective immune system.

Various concurrent diseases can promote persistence of carrier state: diseases of the bile ducts and urinary system in typhoid fever and paratyphoid, chronic diseases of the nasopharynx in diphtheria, helminthiasis in dysentery, etc.

Healthy carriers are persons with asymptomatic infection. Transitory carrier state is characterized by rapid withdrawal of the pathogenic microorganisms from a subject; foci where these microorganisms might multiply are absent. From 30 to 100 carriers can be detected among people surrounding one patient with meningococcal infection of poliomyelitis. Healthy carriers are less dangerous for those who surround them because the pathogenic microorganisms are not usually detected in them during subsequent tests.

The danger of carrier state depends on hygiene and occupation of a carrier. If a carrier of typhoid fever, paratyphoid B, salmonellosis, or dysentery agents is employed at a food catering establishment or a children’s institution, he or she is especially dangerous for the surrounding people. Infected animals are the source of infectious diseases that are common for man and animal. Infection of a human with zoonosis by another person occurs in rare cases. Domestic animals and rodents are dangerous in the epidemiologic aspect. The degree of their danger as the source of infection depends on the character of relations between people and the animals, on the socioeconomic and living conditions. People can get infected during management of diseased animals, cooking and eating their meat (anthrax, brucellosis, Q fever, etc.). Rodents are the source of tularaemia, plague, leptospirosis, rickettsiosis, encephalitis, leishmaniasis and some other diseases.

Main and secondary sources of infection are distinguished in zoonosis. The main source are animals which are a harbour of pathogenic microorganisms and they create natural nidi of tularaemia, plague, and other diseases. Secondary sources of infection become involved periodically in epizootic.

Humans can be infected by wild animals when hunting, during stay in wild environment contaminated with excrements, when drinking water or eating food that may be contaminated with excrements of wild animals. Birds can also be transmitters of infection (omitosis, salmonellosis, etc.).

Pic. 6. Four mechanisms of infection transmission: (А) faecal-oral; (Б) air-bome; (В) transmissive; (Г) contact

 

Mechanism of transmission. For the epidemic to break out it is not sufficient to have a source of infection alone. The causative agent can survive only if it is transmitted from one host to another, because any given macroorganism destroys the pathogenic microorganisms by specific antibodies that are formed in it in response to the ingress of these microorganisms. Death of an individual host terminates the life of the parasitizing microorganisms. The only exception are spore-forming microbes (causative agents of anthrax, tetanus, botulism). The combination of routes by which the pathogenic microorganisms are transmitted from an infected macroorganism to a healthy one is called the mechanism of infection transmission.

Four mechanisms of infection transmission are distinguished according to the primary localization of pathogenic agents in macroorganisms: (1) faecal-oral (intestinal localization); (2) air-bome (airways localization); (3) transmissive (localization in the blood circulating system); (4) contact (transmission of infection through direct contact with another person or environmental objects) (Pic. 6).

Three phases are distinguished in the transmission of infection from one macroorganism to another: (1) excretion from an infected macroorganism; (2) presence in the environment; (3) ingress into a healthy macroorganism .

The method by which microbes are excreted from an infected macroorganism (the first phase) depends on the locus of infection in the infected individual or a carrier. If pathogenic microorganisms reside on respiratory mucosa (influenza, measles, pertussis) they can be released from the patient only with expired air or with droplets of nasopharyngeal mucus. If the infection is localized in the intestine, the pathogenic microorganisms can be excreted with faeces (dysentery). The pathogenic organisms in the blood infect blood-sucking arthropods.The presence of the causative agents outside a macroorganism (the second phase) is connected with various environmental objects. Pathogenic microorganisms excreted from the intestine get on soil, linen, household objects and water, while those liberated from the airways are borne in air. The environmental elements that transmit the pathogenic agent from one person to another are called transmission factors. The pathogenic agent can sometimes be transmitted by direct contact with an infected individual or a carrier (venereal diseases, rabies).

Microorganisms causing infectious diseases (viral hepatitis, rubella, toxoplasmosis, syphilis, etc.) infect the foetus through the placenta (transplacental transmission of infection).

Pathogenic microorganisms can be transmitted mechanically during transfusion of blood or its components (plasma, erythrocytes, fibrinogen, etc.). Infection can be transmitted through inadequately sterilized medical tools (viral hepatitis, hepatitis B, AIDS).

The following main factors are involved in transmission of infection: air, water, foods, soil, utensils, arthropods (living agents).

Air is a factor of transmission of respiratory infections. Contamination occurs mostly in an enclosure where a patient is present. From the source of infection, microorganisms get into air together with droplets-of sputum. They are expelled in great quantities during sneezing, cough and conversation. Droplets of sputum containing the pathogenic microorganisms often remain suspended in the air for hours (smallpox, chickenpox, measles) and can sometimes be carried from one enclosure to another with air streams and precipitate on environmental objects. After drying, sputum droplets infect dust which is then inhaled by a healthy person. Dust infection is feasible only with those microorganisms that persist in the environment and can survive in the absence of water. Tuberculosis mycobacteria, for example, can survive in dust for weeks, and virus of smallpox for years. Agents causing Q fever, anthrax or tularaemia can be transmitted with dust.

Water is another very important medium by which infection can be transmitted. Pathogenic microorganisms can get into water by various routes: with effluents, sewage, with runoff water, due to improper maintenance of wells, laundry, animal watering, getting of dead rodents into water, etc. Spontaneous purification of water depends on ambient temperature, chemical composition, aeration degree, exposure to sun rays, the properties of the microorganisms, and other factors. Infection is transmitted by drinking contaminated water, using this water for domestic purposes, bathing, etc. Water can be the medium for transmission of cholera, typhoid fever, leptospirosis, dysentery, viral hepatitis A, tularaemia, and other diseases. If potable water gets contaminated with faecal sewage, water-borne infection can become epidemic with rapid spreading.

Transmission of infection with food is especially important since pathogenic microorganisms can multiply in foodstaffs. Food can be infected by contact with an infected person or a carrier, by insects or rodents. Food can be infected during improper transportation, storage, and cooking. The form in which a given food is taken is also epidemically important (uncooked natural foods, thermally processed foods, hot or cold foods). Consistency of foodstaff and its popularity are also important factors. Milk and meat are common transmission media. Dairy products (curds, sour cream), vegetables, fruits, berries, bread and other foods that are not cooked before use are important transmission factors as well. Milk, dairy products can transmit dysentery, typhoid fever, brucellosis, tuberculosis, etc. Meat and fish can be an important factor in development of salmonellosis. Intestinal diseases are often transmitted through vegetables, fruits and baked products.

Soil is contaminated by excrements of humans and animals, various wastes, dead humans and animals. Contamination of soil is an important epidemiologic factor because soil is the habitat and site of multiplication of flies, rodents, etc. Eggs of some helminths (ascarides, Trichuris trichiura, hookworms) are incubated in soil. The pathogenic microorganisms of soil can pass into water, vegetables, berries that are eaten by man uncooked.

It is especially dangerous to use faecal sewage to fertilize soil where cucumbers, tomatoes and other vegetables are grown. Tetanus, gangrene, and anthrax are transmitted through soil.

The role played by various environmental objects in transmission of diseases depends on contact with the source of infection, probability of transfer of a contaminated object to a healthy person, and also on the character of chemical and physical effect that a given object can produce on the pathogenic microorganism.

The objects at patient’s room can be the transmitting factor for influenza, tuberculosis, children’s infections, dysentery, typhoid fever, and other diseases. Domestic animals can be the source of infection, while arthropods can transmit infection.

Utensils and household objects such as dishes, cups, plates (in hospitals, canteens, etc.) can become a transmissing factor for tuberculosis, scarlet fever, typhoid fever, diphtheria. Soiled linen and underwear can promote the spread of infection such as scabies, intestinal or droplet infections.

Toys, pencils, and other objects in children’s use are important transmitting factors.

Living objects that transmit infection can be divided into two groups: specific and non-specific (mechanical). Specific carriers are lice, fleas, mosquitoes, ticks, etc. They transmit infection by sucking blood (inoculation) or contaminating human skin with their excrements. Inside specific transmitters of infection, the pathogenic microorganisms multiply, accumulate, and with time become dangerous to the surrounding. A louse, for example, sucks blood of a typhoid fever patient and excretes the pathogenic microorganisms with faeces only in 4-5 days. Non-specific carriers transmit the pathogenic microorganisms by purely mechanical method. Flies, for example, carry microbes of dysentery, typhoid fever, viral hepatitis and some other diseases that are found on their bodily surfaces, on the limbs, in the proboscis and the intestine. Gadflies transmit microbes causing anthrax and tularaemia by their stinging apparatus.

Transmitting factors determine also the third phase of transmission mechanism-inoculation of the successive biological object (host). The pathogenic factor is inhaled with air, ingested with food and water, or is transmitted into the blood by arthropods.

The forms of realization of the transmission mechanism, including the combination of factors involved in spreading of a corresponding disease, are known as the transmission routes of the infective agents.

The following transmission routes are distinguished: contact, air-bome (or dust-bome in some diseases), food- and water-borne, transmission by arthropods and soil, through the placenta, by medical parenteral and other manipulations.

Susceptibility and immunity. Susceptibility of people to a given infection is a very important factor in infection spreading. Susceptibility of an individual or of a community are distinguished. Susceptibility to a disease is a biological property of tissues of a human or an animal, characterized by optimum conditions for multiplication of pathogenic microorganisms. Susceptibility is a species property, that is transmitted by hereditary trait. Many infectious diseases can affect only a certain species of animals. Some anthroponoses, e.g. typhoid fever, scarlet fever, gonorrhoea do not affect animals even after artificial inoculation, because the animals are protected by hereditary (species) immunity.

But hereditary immunity is not an absolute property. Under some unfavourable conditions, immunity of a macroorganism can be altered. For example, overheating or cooling, avitaminosis, or some other unfavourable factors can promote the onset of a disease that would not, under normal conditions, affect man or animal. Pasteur, for example, exposed hens to cold to artificially provoke anthrax in them (the disease that does not affect hens under normal conditions).

The following kinds of immunity are distinguished: hereditary (species), acquired (natural: active, passive; artificial: active, passive).

Some features of epidemic process. An epidemic develops and is maintained only by the interaction between the source of infection, specific mechanism of its transmission, and susceptible population under giveatural and social conditions. The role of these motive forces during subsequent infection is different. The most active is the source of infection, the carrier of the infective factor, the pathogenic microorganisms multiply in it with subsequent release into the environment. The mechanism of infection transmission is decisive. It can be active ingress of the pathogenic factor into a healthy macroorganism through the agency of living carriers, inhalation with air, ingestion with food and water, or persistence of viable pathogenic microorganisms on various non-living objects before they enter another living organism. Susceptibility plays a passive role. In the presence of susceptibility, a person gets infected, while in the absence of such susceptibility a person is not afflicted.

The intensity of an epidemic process can also be different. Three stages of quantitative changes are usually distinguished in the epidemic course: sporadic incidence, epidemic, and pandemic.

Sporadic incidence is a normal (minimal) morbidity characteristic of a given infection for a given country or region. Many infectious diseases occur as single cases.

Group incidence of infectious diseases in a community is assessed in everyday medical practice as an epidemic outburst.

An epidemic is characterized by morbidity that 3-10 times exceeds the sporadic occurrence of a given disease in a given locality; it is also characterized by development of multiple epidemic foci.

Pandemic is characterized by widespread epidemic throughout large territories.

Endemic* characterizes an epidemic qualitatively. An endemic disease constantly occurs among population of a given area. Long existence of any infectious disease in a given country or area can be due to the presence of some natural factors.

Exotic disease is an opposite notion. It is used to designate an infectious disease that does not normally occur in a given country or area and can only be brought from a foreign country.

In veterinary the terms epidemic, pandemic, and endemic are replaced by epizootic, panzootic, and enzootic, respectively.

A focus of infection is a site or area where cases of an infectious disease can occur or has already occurred.

The quantitative and qualitative changes in the epidemic process depend on the natural and social conditions that can activate the source of infection, the transmission factor, or susceptibility of population, thus increasing their epidemiologic activity, or on the contrary, decreasing it.

The effect of natural conditions on the transmission mechanism of infection is especially marked when the pathogenic microorganisms are transmitted by living carriers. Absence of living transmitters (ticks, mosquitoes) during a certain season or reduction of their population reduces the human infection rate, and hence is important for the course of the epidemic process.

Pavlovsky has worked out a theory of natural nidality of transmissible diseases. He showed that many infectious diseases exist iature independently of man, in a certain combination of natural conditions in a given locality, in the presence of warm-blooded animals and arthropods that are depots of the pathogenic microorganisms. For example, ticks transmit encephalitis from diseased animals to healthy ones. Besides, ticks transmit the virus to their posterity.

According to Pavlovsky, natural nidality of transmissible diseases is characterized by indefinitely long existence of the pathogenic microorganisms, their specific transmitters and animals (reservoirs of the pathogenic microorganisms) during renewal of their generations independently of man in various biocenoses, both during the course of their evolution and at a given period of time.

Natural nidi of non-transmissible diseases can exist as well. For example, carriers of leptospirosis are not involved in circulation of the pathogenic microorganisms. Spread of this disease is confined within a certain geographic area where a particular rodent lives. Diseases with natural nidality are characterized by seasonal morbidity which is associated with biology of the carriers.

Many animals give posterity in spring; hence vernal rises in brucellosis morbidity. Plague exists in its latent form during hibernation of gophers and marmots. As rodents return to active life in spring, the infection activates and rapidly spreads among the young generation.

Natural processes have their effect oon-living transmission factors as well. Open water bodies get contaminated more easily with effluents and serve as the source of water-bome epidemic of typhoid fever during the cold season when spontaneous purification of water is slowed down and the microorganisms causing intestinal infections survive for longer periods of time.

Presence of people in enclosures promotes transmission of air-home infections, while wearing warm clothes without proper hygiene of individuals promotes multiplication of lice, carriers of louse-borne and recurrent fever. The effect of the natural factor on susceptibility is insignificant. It only increases or decreases nonspecific body resistance (barrier function of the skin, mucosa, blood, bile, etc.).

The social factor is more important epidemiologically. It includes the concept of living conditions of population: the quality of dwelling, density of population in residential buildings and areas, conveniences (water supply and sewage system), well-being of population, nutrition, cultural standards, sanitation, health-care system, social structure of a community, etc.

The course of an epidemic depends strongly on the living conditions, i.e., on population density, intensity of association between the source of infection and the surrounding people, the character of occupation, traffic, time of detection of carrier state or developing disease, and time of hospitalization or isolation in home conditions. Poor ventilation, overcrowded residence, inadequate insolation and ventilation of rooms and suboptimal sanitation promote spread of tuberculosis and other infectious diseases.

Domestic animals, poultry, and wild animals can be the source of infection. Man can be infected by a domestic animal due to inadequate veterinary control, untimely detection of diseased animals and their isolation, slaughter or treatment. Rodents and wild animals are regularly reduced in their number which decreases considerably their epidemiologic danger.

The condition of water supply and sewage systems, rational and timely cleaning of settlements are important for the spread of intestinal infections such as typhoid fever, paratyphoid, dysentery, cholera, poliomyelitis, viral hepatitis, etc.

Inadequate control and poor organization of food catering is responsible for spread of infectious diseases. Food can be infected by carriers among those who work in food catering, food shops, children’s and medical institutions. People can be infected by meat of diseased cattle and milk and dairy products manufactured from the milk of infected animals.

Labour conditions are often important for the development and spread of infectious diseases. Animal breeders, veterinary workers, those engaged in handling and processing animal materials (leather, wool, etc.), get infected by diseased animals (anthrax, brucellosis, etc.). These diseases can thus be occupational. Besides, factors decreasing resistance of people (hard labour, overcrowded dwellings, cooling and other debilitating factors) can also promote spread of infection.

Migration of population during social conflicts (famine, war), disasters, such as earthquake, flood, or fires, that are associated with destruction of dwellings and worsening of the living conditions and cause mass-scale migration of the victims, intensify the epidemic spread of infectious diseases, that previously occurred as single cases.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2249185/

 

Classification of Infectious Diseases

http://www.bioterrorism.slu.edu/bt/products/bio_epi/scripts/mod3.pdf

http://www.ncbi.nlm.nih.gov/pubmed/21571512

In the 19th century, infectious diseases were classed as contagious (transmissible from person to person), miasmatic (transmitted through air), and contagious-miasmatic. Late in the 19th century, in view of advances made in bacteriology, the diseases were classified according to their aetiology. These classifications could not satisfy clinicians or epidemiologists since diseases with different pathogenesis, clinical course and epidemiologic characteristics were united in one group. Classifications based on clinical and epidemiologic signs proved ineffective too.

The classification proposed by Gromashevsky seems to be more reasonable than many others. It is based on the location of infection in the macroorganism. In accordance with the main sign, that determines the transmission mechanism, all infectious diseases are divided by the author into four groups: (1) intestinal infections; (2) respiratory infections; (3) blood infections; (4) skin infections. According to Gromashevsky, each group is subdivided into anthroponoses and zoonoses; their epidemiology and prevention differ substantially.

Intestinal infections. Intestinal infections are characterized by location of the causative agents in the intestine and their distribution in the environment with excrements. If the causative agent circulates in the blood (typhoid fever, paratyphoid A and B, leptospirosis, viral hepatitis, brucellosis, etc.), it can also be withdrawn through various organs of the body, e. g. the kidneys, lungs, the mammary glands.

As a microbe is released into the environment with faeces, urine, vomitus (cholera), it can cause disease in a healthy person only after ingestion with food or water. In other words, intestinal infections are characterized by the faecal-oral mechanism of transmission.

Maximum incidence of intestinal infections occurs usually during the warm seasons.

The anthroponoses include typhoid fever, paratyphoid, bacterial and amoebic dysentery, cholera, viral hepatitis A, poliomyelitis, helminthiasis (without the second host). The zoonoses include brucellosis, leptospirosis, salmonellosis, botulism, etc.

The main means of control of intestinal infection are sanitary measures that prevent possible transmission of the pathogenic microorganisms with food, water, insects, soiled hands, etc. Timely detection of the diseased and carriers, their removal from food catering and the like establishments is also very important.

Specific immunization is only of secondary importance in intestinal infections.

Most intestinal infections are caused by bacteria, virus, protozoans, and parasites. Stomach bugs and flus are common all over the world, with their incidences being higher in developing countries than developed nations. In the United States alone, however, intestinal infections are the second most common type of infection, second only to the common cold. About 375 million people are affected every year with intestinal infections, of which the most affected are children under the age of 5.

An intestinal infection spreads through contact with the pathogen in food, water, or fecal matter. The most common symptoms of an intestinal infection are diarrhea, abdominal pain, cramps, nausea, and vomiting. Treatment for this is mainly by hydrating the body and relieving the symptoms associated with intestinal infections. In this article, we will discuss the various causes, symptoms and treatment options for intestinal infections.

Causes:

Intestinal infection can be caused by a wide range of microorganisms and pathogens. Some of the most common causative agents of intestinal infections are listed below.

Bacterial infection: Bacterial intestinal infections occur through consumption of food that is contaminated with the infection causing or pathogenic bacteria. Bacterial infections most commonly occur in cases wherein food is not prepared or handled hygienically. Typically, these kinds of infections are seen in places where food is prepared for masses such as cafeterias in schools, fairs, and so on. Bacterial intestinal infection is usually because of not cooking meat products adequately as well as poor hygiene practices such as not washing hands before handling foods, not boiling drinking water and so on. Listed below are some of common causes of intestinal bacterial infection.

·   Cholera, caused by the bacteria vibrio cholera

·   Typhoid (Salmonella enteritis)

·   Parathyroid infections.

·   Shigellosis (Shigella enteritis)

·   E. coli infections

·   Intestinal staph infection (Staphylococcus)

·   Botulism (Clostridium botulinum)

·   Enteritis (Campylobater enteritis)

Viral infections: Viruses also cause a lot of stomach infections as well. The rota virus is the leading cause of intestinal infections in the world and has a high death rate in children under the age of 5. The ill effects of viral intestinal infections are greater in developing nations where general sanitation is very poor. With transmission being through contact, viral intestinal infections can spread very quickly. Some of the common intestinal infections are caused by the following viruses.

·   Rotavirus infections

·   Norovirus infections

·   Adenovirus infections

·   Astrovirus infections

Parasites and protozoans: Parasites and protozoans are another reason for intestinal infections. These however are usually not self-limiting and need medication to kill the pathogens. Some of the common intestinal infections caused by parasites and protozoans are listed below.

·   Amoebiasis (Entamoeba hystolytica)

·   Balantidiasis

·   Giardiasis (Giardia lamblia)

·   Cryptosporidiosis (Cyrptosporidium)

·   Intestinal trichomoniasis

Symptoms:

While there are a few differences in the symptoms of intestinal infections caused by different pathogens, the general symptoms are very similar. Listed below are the symptoms associated with intestinal infections.

·   Diarrhea

·   Watery diarrhea

·   Nausea and vomiting

·   Abdominal pain

·   Cramps in stomach

·   Loss of appetite

·   Blood or mucus in stools

·   Black or abnormally colored stools

·   High fever

·   Dehydration (thirst, fatigue, dizziness, feeling light headed, dark urine, and dry skin)

·   Headache

·   Fever

·   Chills

Diagnosis:

As many microorganisms cause intestinal infections, diagnosing the cause can be quite tricky. The best way to figure out what kind of infection you have is through a stool test. This is done by taking a sample of the stool and testing it for the presence of certain pathogens.

Respiratory infections. This group includes diseases whose causative agents parasitize on the respiratory mucosa and are liberated into the environment with droplets of sputum during sneezing, cough, loud talks, or noisy respiration.

People get infected when the microbes contained in sputum get on the mucosa of the upper airways. If the causative agent is unstable in the environment, a person can only be infected by lose contact with the sick or carrier (pertussis).

Pathogenic microorganisms causing some diseases can persist for a period of time in an enclosure where the sick is present. Infected particles of sputum or mucus can dry and be suspended in the air. Some diseases of this group can spread through contaminated linen, underwear, utensils, toys, etc.

Since susceptibility of people, and especially of children to respiratory infection is very high, and since the infection is easily transmitted from the diseased (or carriers) to healthy people, almost entire population of a given area usually gets infected, and some people can be infected several times. Some diseases of this group form a special subgroup of children’s infections (diphtheria, scarlet fever, measles, pertussis, epidemic parotitis, chickenpox, rubella). A durable immunity is usually induced in children who sustained these diseases. The main measure to control respiratory infections is to increase non-susceptibility of population, especially of children, by specific immunization.

It is important to timely reveal the sick and carriers, and also to break the mechanism of infection transmission: control of overcrowding, proper ventilation and isolation of enclosures, using UV-lamps, wearing masks, respirators, disinfection, and the like.

Blood infections. The diseases of this group are transmitted by blood-sucking insects, such as fleas, mosquitoes, ticks, etc., which bite people and introduce the pathogenic agent into the blood.

Tick-bome encephalitis, Japanese В encephalitis and some other infections are characterized by natural nidality which is due to specific geographic, climatic, soil and other conditions of infection transmission. The morbidity is the highest during the warm season which coincides with the maximum activity of the transmitters-ticks, mosquitoes, etc.

Control of blood infections includes altering natural conditions, improvement of soils, draining swamps, destroying sites where the insects multiply, disinsection measures against mosquitoes, ticks, etc., detoxication of sources of infection by their isolation and treatment, carrying out preventive measures.

If the source of infection are rodents, measures to control them are taken.

Active immunization is also effective.

Skin infections. The diseases of this group occur as a result of contamination of the skin or mucosa with the pathogenic microorganisms. They can remain at the portal of infection (tetanus, dermatomycoses), or affect the skin, enter the body and be carried to various organs and tissues with the circulating blood (erysipelas, anthrax). The transmitting factors can include bed linen, clothes, plates and dishes and other utensils, that can be contaminated with mucus, pus or scales. Pathogenic microorganisms causing venereal diseases, rabies, AIDS, and some other diseases are transmitted without the agency of the environmental objects. Wound infections are characterized by damage to the skin as a result of injury (tetanus, erysipelas).

The main measures to control skin infections include isolation and treatment of the source of infection, killing diseased animals, homeless dogs and cats, improving sanitation and living conditions of population, personal hygiene, control of traumatism, and specific prophylaxis.

 

DISINFECTION MEASURES

http://www.scribd.com/doc/13573922/8/Disinfection-Measures

The subject matter of disinfection are methods and means of control (or eradication) of the causative agents of infection in various objects and substrates of the environment, and also means of accomplish­ment of these means and measures.

Disinfection includes three concepts: (1) disinfection proper; (2) disinsection (control of the arthropods transmitting infection); (3) deratization (rodent control).

Depending on the mechanism of infection transmission, it may be necessary to perform disinfection alone (respiratory infections); disinfection and disinsection (intestinal infections); disinsection (louse-bome fever, malaria); disinfection, disinsection and rodent control (plague). Besides, sterilization is also used. Sterilization implies complete eradication of pathogenic and non-pathogenic microorganisms (spo­res included) in the environment. Sterilization is used for treatment of surgical, gynaecological, stomatological and other tools, apparatuses, dressing materials, linen, needles, syringes, etc. Nutrient media, laboratory ware, tools and instruments are sterilized in microbiology.

Before sterilization, all objects are first disinfected and cleaned with detergents, hydrogen peroxide and similar solutions.

Several disinfection methods are known. Glass, metal, thermally stable polymers and rubber articles can be sterilized by boiling for 30 minutes, by treatment in special sterilizers at a temperature of 110 ±2 °С and elevated pressure of steam.

Special sterilization units must be provided for regular sterilization of tools, instruments and other materials.

Disinfection

Disinfection includes focal and preventive disinfection.

Focal disinfection is necessary if infection develops in a family, children’s institution, or any other public institution. It implies current and final disinfection.

Current disinfection includes regular disinfection measures taken during the entire period of presence of a patient or a carrier in a given enclosure. The object of current disinfection is to prevent the spread of the infection.

If, for some reason, the patient is not hospitalized, he must be isolated in a separate room or his bed screened from the other family. Only indispensable objects may be left in the room where the patient remains. The patient must use a separate towel, dishes, bed-pan and the like. In intestinal infections, excrements of the patient (urine, faeces, vomitus) must be mixed with l/5th volume of dry lime chloride, or the excrements should be poured over with two volumes of a 10-20 per cent lime chloride solution or a 5 per cent chloramine or lysol solution. The room must be cleaned 2 or 3 times a day using a moist cloth and aired properly. A 2 per cent soap-soda or 0.2 per cent chloramine solution should be used for the purpose. The concentration of chloramine solution depends on the sensitivity of the pathogenic microbes to disinfectants. Glass ware and dishes used by the patient should be boiled for 15 minutes. Disinfection should be done by a person who takes care of the patient (after being properly instructed) or medical personnel.

Final disinfection is carried out in the focus of those infections whose causative agents are stable in the environment (typhoid fever, viral hepatitis, cholera, diphtheria, poliomyelitis, plague, etc.). Final disinfection in the focus of paratyphoid and quarantine infection should be performed simultaneously with evacuation of the patient. In the focus of other infection, disinfection should be done not later than in 6 hours (in towns and cities) or 12 hours (in rural areas) after evacuation of the patient. In addition to disinfection, disinsection should also be carried out in foci of intestinal infections (flies should be destroyed). This measure should be taken after hospitalization of the patient, after his recovery or death (if the patient remained at home). Final disinfection is also necessary after discharge of the patient from the hospital, after removal of the diseased from children’s or other institution. Final disinfection should be performed by representatives of a sanitary-epidemiologic post or station.

As soon as the disinfection brigade has arrived at the site of disinfection, the scope of work must be determined and a solution of required concentration prepared. If flies are found in the enclosure, disinsection should be performed after the windows and the doors are closed tightly. After disinsection has been performed, the window can be opened, and the patient’s belongings (linen, clothes, carpets, toys) are put into special bags for disinfection in special chambers.

Disinfection should be done in the following order: objects that were used for care of the patient, and bis excrements are disinfected first, then follows disinfection of remaining food, linen, toys; pieces of furniture. After decontamination of all objects in the room, the floor and the walls are sprayed with the disinfectant in the room of the patient and the adjacent premises. In 30-50 minutes, the rooms are treated with a disinfectant solution. Depending on pathogenicity of the causative agent, disinfection can be done by the family themselves after being properly instructed by the medical personnel.

Preventive disinfection is necessary in all cases regardless of the presence or absence of infectious diseases in a given district or area. Examples of preventive disinfection are daily cleaning at medical institutions, hospitals, schools and other children’s institutions, public establishments using a 0.5 per cent chloramine solution. Pasteurization of milk, chlorination of water, washing hands before meals, and the like are also preventive disinfection measures.

Mechanical, physical, chemical, and biologic methods and means are used for disinfection.

Mechanical methods include laundry, washing hands, wet cleaning of floors, removal of dust with wet clothes or using a vacuum cleaner. Pathogenic microbes are partly removed by all these methods. A common physical method of disinfection is boiling. It is used to treat linen, utensils, drinking water, food, toys, surgical tools, and the like. The bactericidal effect increases when boiling is done in a 2 per cent sodium hydrocarbonate or soap-soda solution for 15 minutes and over. The time of boiling depends on stability of a particular pathogenic microorganism to high temperature. Contaminated linen or dishes used by an anthrax patient should be boiled for 60 minutes. Dead animals, wastes, cheap materials, used dressing, etc. should be burned. Dead people should also be burned.

Steam is also used for disinfection. It penetrates into the depth of tissues to destroy the microbes and their spores. Steam is used in special disinfection chambers and autoclaves. Saturated water va­pour is very effective.

Treatment at a temperature of 70-80 °С for 30 minutes (pasteuriza­tion) kills vegetative forms of microbes, while spores survive.

Linen and other textile articles can be disinfected in home conditions by hot ironing on both sides. It is even more effective if textile fabrics are first sprayed with water.

U-V lamps are used to disinfect air in enclosures (in hospitals, children’s institutions, in food industry, etc.). If people are present in the enclosure, the radiation must be directed only into the upper or lower layers of air.

Direct sun rays kill many pathogenic microbes. This simple method must be utilized as much as possible.

The chemical method of disinfection includes the use of various chemicals that destroy pathogenic agents found on the surface and inside various objects of the environment and in various substrates, such as faeces, pus, sputum, and the like.

Chlorine- and oxygen-containing substances, phenols, acids, alkalis, hydrogen peroxide, formaldehyde are commonly used as chemical disinfectants.

Chlorine-containing chemicals. Lime chloride is a white substance with a pungent odour of chlorine, insoluble in water. The active chlorine content varies from 36 to 28 per cent (minimum 25 per cent). When stored, the substance loses part of its active chlorine and it should therefore be kept in tight containers in the dark. The concentration of clarified solution of lime chloride varies from 0.2 to 20 per cent, depending on the properties of the objects to be treated and stability of the pathogenic microorganisms. A 10 per cent clarified solution of lime chloride is prepared by dissolving 1 kg of dry lime chloride in cold water to make 10 litres. The solution is stirred with a wooden stick, then it is allowed to stand in a tightly closed glass or enameled container for 24 hours. The clarified solution is passed through a dense cloth and the sediment is discarded. Thus prepared solution should be kept in a dark air-tight bottle for not more than 6 days.

If lime chloride contains less than 25 per cent of active chlorine (not less than 16 per cent), the amount of this substance necessary to prepare a 10 per cent clarified solution should be determined using the following formula:

x = a*25/b,

where x is the necessary amount of lime chloride, in kg; a is the quantity of lime chloride containing 25 per cent of active chlorine which is necessary to prepare a 10 per cent solution, in kg; and b is the content of active chlorine in lime chloride, in per cent.

Dry lime chloride is also used for disinfection of faeces (2°0 g of powder per 1 litre) and urine (10 g per 1 litre).

Commercial lime chloride can be stored for years in a dry place (used as 1-3 per cent solution).

Chloramine (monochloramine, dichloramine) contains from 24 to 28.4 per cent of active chlorine. The substance is soluble in water. Chloramine solutions are widely used for preventive and focal disinfection (0.2-5 per cent solution). Aqueous solutions are prepared immediately before use. They remain active for 15 days.

Activated solutions of chlorine-containing substances are widely used for disinfection. These are prepared by mixing lime chloride and chloramine with ammonium chloride, ammonium sulphate or ammonium nitrate taken in the ratio of 1:1 or 1:2. Ammonia water (10-20 per cent) can also be used as an activator (added in the ratio of 1:8 or 1:16). The reaction is vigorous. Nascent chlorine kills the microorganisms and their spores. Activated solution can thus be used in lower concentrations and the time of exposure can be shorter.

Sulphochlorantin (thermally stable) is a creamy powder with an odour of chlorine. It contains 15.6 per cent of active chlorine; remains active for more than a year if stored in a dark dry place. The activity of sulphochlorantin is 5-Ю times higher than that of chloramine. The preparation is used as 0.1-0.2 per cent solution for current and final disinfection in foci of intestinal and air-bome infections of viral and bacterial aetiology.

A Soviet-made preparation DP-2 is a white powder with an odour of chlorine. It contains 40 per cent of active chlorine. The expiration term is 3 years. Aqueous solutions of the preparation remain active for 24 hours. DP-2 is used as 0.02-0.08 per cent aqueous solution. The amount of the preparation (in grams) required to prepare one litre of the working solution depends on the concentration of active chlorine. If, for example, the active chlorine content is 40 per cent, 0.5 g of the preparation is necessary to prepare 1 litre of a 0.02 per cent solution; 1.0 g of the preparation should be dissolved in 1 litre of water to prepare a 0.04 per cent solution, etc. DP-2 is used for current, final and preventive disinfection in intestinal, and air-bome infections of bacterial and viral aetiology, fungal diseases, anthrax, plague, etc.

The DP-2 preparation irritates mucosa of the eyes and the upper airways. Measures of individual protection should therefore be used:

overalls, gloves, goggles, respirators and the like equipment.

Calcium hypochlorite (neutral salt) is a white powder containing 50, 60 and 70 per cent of active chlorine, depending on commercial grade. It is used as 1-5 per cent aqueous solution for disinfection of buildings.

Chlordesin is a white powder with a faint odour of chlorine. The active principle is a potassium salt of dichloroisocyanuric acid. The preparation contains from 10 to 12 per cent of active chlorine. It is used as a 0.5-2 per cent solution; it acts as a detergent and disinfectant; does not spoil the treated objects.

Oxygen-containing chemicals. Hydrogen peroxide is produced as 27.5-40 per cent solution. It is a colourless liquid decomposing spontaneously into water and oxygen. Its 0.5-6 per cent solution is used as disinfectant. In order to prepare a 3 per cent solution, 9 parts of water are mixed with one part of commercial hydrogen peroxide. A 6 per cent solution is prepared from 8 parts of water and 2 parts of hydrogen peroxide. Concentrated solutions of hydrogen peroxide can cause bums on the skin; overalls, goggless and rubber gloves should therefore be worn.

Desoxon is a colourless liquid with a specific acetic odour; readily soluble in water, alcohol and other solvents. Aqueous solutions are prepared immediately before use because the active principle is rapidly inactivated in solution. The preparation is used for preven­tive, current and final disinfection in hospitals and other medical institutions, in foci of intestinal and air-bome infections of viral and bacterial aetiology. It is used for sterilization of plastic, glass, and corrosion-proof articles. The concentration of the working solution varies from 0.05 to 0.1 per cent.

Phenol (crystalline carbolic acid) is usually stored as aqueous solution (90 parts of the acid in 10 parts of water). The acid is used as a 3-5 per cent solution to disinfect contaminated materials in clinical and microbiological laboratories.

Lysol is a brown-red oily liquid. Its commercial solution contains not less than 47.5 per cent of soluble cresols, about 50 per cent of soft potash soap and water. It is used as a hot 3-10 per cent aqueous solution.

Hydrochloric acid kills pathogenic microorganisms and their spores. The acid is used to decontaminate hide and pelt of anthrax animals.

Nitric acid is used as a 2 per cent solution to disinfect shaving tools by keeping them in the acid at a temperature of 40 °С for 2 hours.

Sodium hydroxide is readily soluble in water. It is used as a hot 1-10 per cent solution to disinfect rooms, stores, and other enclosures where food or animal raw materials are processed. The solution is effective against anthrax.

Formalin is a 40 per cent solution of formaldehyde. It is used to prepare a 2 per cent solution to disinfect chemical fibres and textiles, instruments, and the like.

Biological disinfection is commonly used in laboratory during cultivation of microorganisms (causing pertussis) iutrient media (casein-carbon agar). In order to inhibit the growth of extraneous flora, penicillin is added to the nutrient medium.

Pic. 1. Bix

Pic. 2. Sterylezator

Addition 1

METHODS, WAYS and MEASURES of DISINFECTION

Object of disinfection	Way of disinfection	Way of disinfecting	Exposition, minutes.	Norm of an expense
Allocation of the patient’s excrements, vomiting, spitting.	Mixing with the following stirring	Lime or lime chloride whitening termostable or Hypochlorid of calcium Neutral hypochlorid of calcium Hypochlorid of calcium technical mark A mark B 15 % a solution of metasilikat sodium	60 120   30 120 120 240	200 gm/kg 150 gm/kg   200 gm/kg 200 gm/kg 250 gm/kg ratio 2:1
Urine	The same	Lime or lime chloride whitening termolabil	15	10 gm/L
Utensils from the excrements (pots, bedpan ,urine container)	Immersing in one of dissolution with the following washing	1 % a solution of chloramines 1 % the covered solution of lime chloride or lime whitening termolabil 0,2 % a solution sulfachlorantin 2 % solution of amfolan 2 % solution of metylsilikat sodium	60 60 90 90 90
Utensils of the patient (tea, table)	boiling	2 % a soda solution	15 from the moment of boiling
The utensils, released from the rests of food	Immersing in dissolution	0,5-1 % solution of chloramines   0,5 % the covered solution of lime chloride or lime chloride whitening, termolabil 0,1 % a solution sulfachlorantine 3 % solution of peroxide of hydrogen with 0,5 % of washing-up liquid of 0,5 % a solution of chlorcine 1 % a solution of chlorcine  3 % a solution of nirtane 0,5 % a solution of empholan	60   60   30 120 60 30 60 30	2 L on the complete set of utensils _”_
The rests of food	boiling mixing	lime or chloride lime whitening termolabil	15
Room, things for the patient supervision which are cannot be boiled, hot water bag, bedpan, oil-cloth bibs, doors, pens.	At the current disinfection of wiping by a cloth, watering in one of dissolutionsAt final disinfection of rooms subjects of the domestic use wipe or richly irrigate from the hydroboard with one of solutions	0,5 % solution of chloramines   1 % solution of chloramines  0,5 % the covered solution lime chloride whitening termolabil 1 % a solution lime chloride or lime of whitening, termolabil, 0,1 % a solution of sulfochlorantine 3 % solution of peroxide of hydrogen from 0,5 % of a washing-up liquid 0,5 % a solution of chlorcine 1 % solution of chlorcine 0,1 %solution of DP-2  3 % a solution of nirtan 0,5 % a solution of emfolan	60   60 60   60   60 60 120 60 30 60 60	200 mL / m2 wiping   300 mL / m2 wiping _”_  – 300 ml / m2 wiping _”_ _”_ _”_ _”_ _”_
Linen without seen traces of faecal pollution	Boiling   Soaking in one of dissolutions with the following washing and rinsing	2 % a soda solution of any washing-up liquid 0,2 % a solution of chloramines 0,5 solution of chloramines 0,1 % a solution of sulfachlorantine 0,2 % solution of sulfachlorantine 0,5 % a solution of chlorcine 0,5 % solution of amfolan	15  120  60 _”_ 30 30 30	4 L/kg _”_ _”_ _”_ _”_ _”_
The linen polluted with excrements	Boiling Soaking in one of dissolutions with the following washing and rinsing	2 % a soda solution 1 % a solution of chloramines 0,2 % a solution of sulfachlorantine  1 % solution of chlorcine  0,5 % solution of amfolan	15 240  90 120 60	4 L/kg _”_ _”_ _”_ _”_
Toys	Boiling (except for plastic), immersing or wiping by a cloth, watered in	0,2 % soda solution 0,5 % solution of chloramines 0,5 % whitening solution lime chloride whitening. termolabil.	15 60 60	Full immersing of 200 ml / m2 or wiping
	solution, with the following washing	0,1 % solution of chlorantine 0,5 % solution of chlorcine 3 % solution of nirtan 1 % solution of emfolan	30 30 30 30	_”_ _”_ _”_ _”_
Bed (pillows, blankets, mattresses)	Disinfecting in chambers	Pairaired at temperature 80-90 °С	35	60 kg / m2 of the area of floor of the chamber
Cloth, footwear, products of chemical fibre	Disinfecting in chambers	Pairformalined at temperature 57-59 °С	90	60 kg / m2 of the area of floor of the chamber
Waters after the patient washing, after utensils washing	Mixing with the following stirring	Lime chloride or lime of whitening termolabil,	30	50 gm/10 l
The sanitary-engineering equipment (baths, bowls, toilet bowls etc.)	Double wiping with a cloth, watered in one of the dissolutions Wiping by the cloth on which put washing, dispreparates with the following washing	Dissolutions, used at disinfecting rooms Дихлор-1, Білка, Блиск-2, Саніта, Дезус etc..	60 15 15 25 15 15	500 mL / m2 0,5 gm/m2 of the surface 0,5 gm/m2 of the surface – “-
Rubbish	Firening Fill in one of the dissolutions	10 % the covered solution lime chloride or lime of whitening termolabil 20 % lime-chloride milk	120    60	In ratio 2:1   – “-
Outdoor lavatories, dirty gaps, garbage gaps and the garbage boxes	Irrigate one of the dissolutions	10 % the covered solution of lime chloride or lime of whitening termolabil	60	500 mL / m2

 

               а                                                           b                                                     c

              d                                                                          e                                                                                      f

 

Pic. 5. Hand pump for dispurse of disinfection solutions

а – sprayer РR-3, b – desinfal, c – bag carying sprayer, d – аutomax,

e – water pump, f – ventilator sprayer

 

                              а                                                                                                      b

 

 

                                      c                                                                                                                                d

 

Pic. 6. Mechanical equipment for disinfection

а – sprayer RND   b–motor sprayer

c – combined set of KDO on motorcycle   d – electrical sprayer EP 03

 

 

                                                                                                              а                                                                                                                     b

                                                                                                                      c                                                                                                                        d

Pic. 8. Hospital disinfection cameras shape

а – VFC-5/2-6, b – KDF3, c – KDFC 5, г – CHDDI

 

 Pic. 9. Portable electrical ULV chemical sprayer «cyclone».

 

 

 

 

 

 

                         

                             a                                                                               d

                b                                                                         e

                     c                                                                       f                

 

Pic. 12. Mechanical equipment for catching of roddents

а – spring hook, b – metal hook, c – arch hook, d – net frame for mice, e – automatic frame for rats, f– frame for rats

http://www.bukisa.com/articles/334643_the-methods-of-sterilization-and-sanitation

http://www.accessexcellence.org/AE/AEC/CC/chance_activity.php

http://www.epa.gov/ogwdw/disinfection/lt2/pdfs/guide_lt2_uvguidance.pdf

 

SCHEDULED IMMUNOPROPHYLAXIS AND URGENT PREVENTION. THEIR ORGANIZATION, WAYS OF REALIZATION

 

Susceptibility and immunity.

http://www.psy.cmu.edu/~scohen/marslandbachen02.pdf

Susceptibility of people to a given infection is a very important factor in infection spreading. Susceptibility of an individual or of a community are distinguished. Susceptibility to a disease is a biological property of tissues of a human or an animal, characterized by optimum conditions for multiplication of pathogenic microorganisms. Susceptibility is a species property, that is transmitted by hereditary trait. Many infectious diseases can affect only a certain species of animals. Some anthroponoses, e.g. typhoid fever, scarlet fever, gonorrhoea do not affect animals even after artificial inoculation, because the animals are protected by hereditary (species) immunity.

But hereditary immunity is not an absolute property. Under some unfavourable conditions, immunity of a macroorganism can be altered. For example, overheating or cooling, avitaminosis, or some other unfavourable factors can promote the onset of a disease that would not, under normal conditions, affect man or animal. Pasteur, for example, exposed hens to cold to artificially provoke anthrax in them (the disease that does not affect hens under normal conditions).

The following kinds of immunity are distinguished: hereditary (species), acquired (natural: active, passive; artificial: active, passive).

Acquired immunity, both natural and artificial, is specific because specific antibodies are produced in an infected macroorganism in response to the ingress of foreign antigens.

Natural active immunity is formed in a macroorganism as a result of a sustained disease (postinfection or acquired immunity). Duration of such immunity varies from several years (measles, chickenpox, plague, tularaemia) to a year (brucellosis, dysentery). Natural active immunity can sometimes develop without apparent illness. It is formed as a result of an asymptomatic disease or multiple ingress of the pathogenic microorganisms that are unable to provoke a clinically manifest disease. (For example, only 0.2-0.5 per cent of the infected, develop meningococcal infection; the percentage is even lower in poliomyelitis.)

Natural passive immunity is acquired by a foetus from bis mother through the placenta (intrauterine immunity). A newbom acquires it with mother’s milk. This immunity is not stable and persists only for 6-8 months to protect the nursling from some infectious diseases (measles, rubella, etc.).

Artificial active (postvaccinal) immunity is created by inoculation with bacteria, their toxins, or virus (antigen) attenuated or inactuated by various techniques. After administration into a macroorganism, they undergo active re-organization which is aimed at production of substances that destroy the pathogenic microorganisms or their toxins (antibodies, antitoxins). Artificial active immunity develops during 3-4 weeks and persists from 6 months to 5 years. The effect of postvaccinal immunity on the course of an epidemic process depends on the scale of vaccination of population, especially of children (against tuberculosis, diphtheria, pertussis, measles, poliomyelitis, and other infections). Vaccination is considered successful if at least 80 per cent of the vaccinated develop adequate immunity (according to WHO experts).

Artificial passive immunity is created by administration of antibodies (sera, immunoglobulins). It persists for 3-4 weeks and then the antibodies are destroyed and excreted from the body. Passive immunization is necessary in situations where the danger of infection exists or if the macroorganism is already infected (in foci of measles, pertussis, etc.).

Depending on a particular antigen, the following types of immunity are distinguished: antimicrobial, antitoxic, and antiviral.

Depending on the period within which the infectious microorganisms are removed from the body, immunity can be sterile (the macroorganism is freed from the pathogenic agent after cure) and non-sterile (immunity persists until the pathogenic microorganism remains in the macroorganism).

Apart from individual immunity there also exists community (herd) immunity.

Community immunity is non-susceptibility of a community to a given infection. This type of immunity is created by specific prophylactic and other measures that are taken by health-care services, and also by improvement of well-being of population. Susceptibility to a disease, the course of infection, and duration of immunity depend on diet (that must be rich in proteins and vitamins), ambient temperature, physiological condition of an individual, pre-existing or attending diseases.

Non-susceptibility to smallpox, for example, was formerly attained by compulsory mass-scale immunization. After eradication of smallpox in the world, smallpox vaccination is no longer necessary.

The immunologic structure of population is the ratio of the number of people susceptible to a given infection to the number of those non-susceptible to the disease. This ratio is determined by various immunologic, serologic, and allergic reactions. If the number of susceptible people is not great, they are surrounded by the majority of non-susceptible persons and the disease is thus not spread.

http://www.homeoint.org/books4/close/chapter07.htm

http://asadl.org/jasa/resource/1/jasman/v85/i3/p1255_s1?isAuthorized=no

http://ps.fass.org/content/76/5/677.abstract

http://www.jstor.org/discover/10.2307/3272186?uid=3739232&uid=2129&uid=2&uid=70&uid=4&sid=55948856923

 

Measures to increase non-susceptibility of population.

Non-susceptibility of population is increased by improving general non-specific resistance of population by improving the living and labour conditions, nutrition, physical training, health envigorating measures and by creating specific immunity through preventive vaccination. The ancients noted that people who had sustained many infectious diseases became non-susceptible to repeated infection with the same disease. In the Orient (China, India) they believed that if a person could sustain a mild form of an infection, it could protect him from dangerous diseases during epidemic outbursts. They protected themselves from smallpox by rubbing the content of smallpox lesions into the skin or ingested crusts (variolation), or put contaminated underwear of smallpox patients on healthy children, etc.

In Europe, first attempts to create artificial non-susceptibility to infectious diseases were made in the 18th century. Variolation was practiced in England, Germany, Italy, France, Russia and some other countries. Samoilovich, for example, suggested that population could be immunized by the bubonic contents of plague patients.

The discovery of the English physician Edward Jenner has become a turn point in the teaching of artificial immunity. In 1796, Jenner developed a process of producing immunity to smallpox by inoculation with cowpox vaccine.

Louis Pasteur produced a live vaccine against anthrax by attenuating the causative agents at high temperature. His principle was used successfully by other investigators who also manufactured live vaccines. Virulence of tuberculosis bacteria has thus been decreased by multiple cultivation of the starting culture on bile-potato media.

Most effective proved the method of controlled variability of microbes and selection of low-virulence and highly immunogenic strains. Artificial active immunity is now induced by vaccines (from Latin vacca, cow and vaccina, cowpox); the method is known as vaccination.

 

The following preparations are used to prevent infectious diseases:

live vaccines prepared from attenuated non-pathogenic microorganisms or viruses; inactivated vaccines prepared from inactive cultures of pathogenic microorganisms causing infectious diseases; chemical vaccines (antigens), isolated from microorganisms by various chemical methods; toxoids, prepared by treating toxins (the poisons produced by microorganisms causing infectious diseases) with formaldehyde.

Vaccines can produce immunity against a given infectious disease or can be polyvalent, i. e., effective against several infectious diseases. Adsorbed vaccines are popular. Aluminium hydroxide is used as an adsorbent. Adsorbed vaccines induce active durable immunity in the vaccinated macroorganism by creating a depot at the site of administration of the antigen, which is slowly absorbed.

Live vaccines are used to create specific immunity against poliomyelitis, measles, influenza, tuberculosis, brucellosis, plague, tularaemia, anthrax, Q fever, skin leishmaniasis, epidemic parotitis, and some other diseases.

Live vaccines prepared from attenuated vaccine strains of microorganisms are more effective than inactivated chemical vaccines. Immunity induced by live vaccines is about the same as produced by normal infection. Live vaccines are given in a single dose intra-cutaneously, subcutaneously, per os, into the nose or by scarification. The disadvantage of live vaccines is that they should be stored and transported at a temperature not exceeding 4-8 °С.

http://www.pbs.org/wgbh/nova/bioterror/vacc_smallpox.html

Inactivated vaccines are prepared from highly virulent strains with adequate antigen properties. They are used to prevent typhoid fever, paratyphoid, cholera, influenza, pertussis, tick-borne encephalitis, and some other diseases. Depending on the microorganism species, various methods are used to inactivate them. The microorganisms can be treated with formaldehyde, acetone, alcohol, merthiolate, or at high temperature. Efficacy of inactivated vaccines is lower than that of live vaccines although there are some highly effective inactivated vaccines as well. Inactivated vaccines are injected subcutaneously. Adsorbed vaccines are given intramuscularly. Inactivated vaccines are more stable in storage. They can be kept at temperatures from 2 to 10 °С.

http://www.pbs.org/wgbh/nova/bioterror/vacc_measles.html

Chemical vaccines are more active immunologically. These are specific antigens extracted chemically from microbial cells. Adsorbed chemical vaccines are used for active immunization against typhoid fever, paratyphoid and other diseases.

Toxoids are formaldehyde-treated exotoxins of the microorganisms causing diphtheria, tetanus, cholera, botulism, and other diseases. Diphtheria and tetanus toxoid is used in the adsorbed form. Toxoids are highly efficacious. When administered into a macroorganism, the vaccine induces an active immunity against a particular infection. Live vaccines produce an immunity that lasts from 6 months to 5 years. Duration of immunity produced by inactivated vaccines is from a few months to a year.

http://www.pbs.org/wgbh/nova/bioterror/vacc_tetanus.html

Immune sera and their active fractions (mainly immunoglobulins) induce passive immunity. Immune sera and immunoglobulins are prepared from blood of hyperimmune animals and from people who have sustained a particular disease or have been immunized otherwise. Passive immunization is used for urgent prophylaxis of people who are infected or supposed to be infected, and also for treatment of the corresponding infectious disease. The effect of immune sera and immunoglobulins lasts from 3 to 4 weeks. They are given intramuscularly.

Bacteriophages are used to prevent and treat some infectious diseases. Bacteriophages are strictly specific toward separate species and even types of.bacteria.

The preparations can be given parenterally (percutaneously, intracutaneously, subcutaneously, intramuscularly, intravenously) or enterally (per os), intranasally or by inhalation (aerosols).

When giving vaccines parenterally, it is necessary to observe sterile conditions and to adhere to the rules specified for injection of a particular vaccine. Jet injections are widely used now: the preparations are administered into the skin, subcutaneously and intramuscularly using various syringes.

When given in the liquid state or in tablets, the vaccine should be taken together with water.

Vaccination should be performed by a physician or secondary medical personnel after thorough examination of persons to be vaccinated in order to reveal possible contraindications, the presence of allergic reactions to medicines, food, etc.

The main contraindications to prophylactic vaccination are as follows: (1) acute fever; concurrent diseases attended by fever; (2) recently sustained infections; (3) chronic diseases such as tuberculosis, heart diseases, severe diseases of the kidneys, liver, stomach or other internal organs; (4) second half of pregnancy; (5) first nursing period; (6) allergic diseases and states (bronchial asthma, hypersensitivity to some foods, and the like).

Vaccination can induce various reactions. These can be malaise, fever, nausea, vomiting, headache and other general symptoms; a local reaction can develop: inflammation at the site of injection (hyperaemia, oedema, infiltration, regional lymphadenitis). Pathology can also develop in response to vaccination; such pathologies are regarded as postvaccination complications. They are divided into the following groups: (1) complications developing secondary to vaccination; (2) complications due to aseptic conditions of vaccination; (3) exacerbation of a pre-existing disease.

Prevention of postvaccination complications includes: strict observation of aseptic vaccination conditions, adherence to the schedule of vaccination, timely treatment of pathological states (anaemia, rickets, skin diseases, etc.), timely revealing of contraindications to vaccination, and screening out the sick or asthenic persons. All cases with severe reactions to vaccination should be reported to higher authorities. If vaccination is performed by scarification, the results are not always positive, and the vaccine must therefore be tested. The results of vaccination should be assessed at various terms, depending on a particular disease against which a person is vaccinated. The result of vaccination against, e. g. anthrax, should be assessed in 2-3 days.

Vaccination should be performed according to a predetermined plan, or for special epidemiologic indications. Planned vaccination is performed against tuberculosis, diphtheria, tetanus, pertussis, poliomyelitis, measles, epidemic parotitis, and against some other infections within the confinement of separate districts or population groups, regardless of the presence or absence of a given disease. Vaccination for special epidemiologic indications are performed in the presence of direct danger of spreading of a particular infection. Vaccination reports must be compiled and special entries made in histories.

Making Vaccines

Today there is mounting concern about the threat of a bioterrorist attack using smallpox — so much concern that in October 2001 the American government decided to order enough vaccine to protect every U.S. citizen.

Smallpox has a fearsome reputation, having killed more people in history than any other infectious disease. It was quite a victory, then, when English physician Edward Jenner developed an inoculation against smallpox in 1796. Armed with the knowledge that milkmaids who had been exposed to cowpox, a relatively mild affliction, didn’t come down with smallpox, Jenner intentionally infected an eight-year-old boy with cowpox. Two months later he infected the boy again, this time with smallpox. As Jenner expected, the child didn’t come down with the disease — he was immune. Although Jenner’s experiment was highly unethical, especially by today’s standards, it did lead to widespread inoculations against the feared disease. He called his new procedure vaccination, after vacca, which is Latin for cow.

A vaccine works by generating an immune response in the body against some kind of pathogen — a virus or bacteria or some other agent that causes disease. Normally when a pathogen invades the body, the immune system works to get rid of the pathogen. Often, though, the immune system gets a slow start, which gives the pathogen time to multiply and wreak havoc. What a vaccine does is expose the immune system to a less-threatening version of a pathogen and, in effect, prime it to recognize and quickly eliminate the pathogen’s harmful counterpart, should it ever invade the body.

This feature lets you create six vaccines in your own virtual laboratory, using a different technique to produce each one.

·        Making Vaccines

 

Here are the instructions you need to create six different types of vaccines. To find out how a vaccine is made, select a pathogen below.

Live vaccines contain living pathogens. These pathogens invade cells within the body and use those cells to produce many copies of themselves, just as their more harmful counterparts would. The “similar pathogen” and “attenuated” vaccines discussed in this feature are examples of live vaccines. Although these vaccines trigger a full immune response, there is a small risk of the viruses within evolving into more-virulent strains. Non-live vaccines contain agents that do not reproduce in the body. “Killed,” “subunit,” and “toxoid” are examples of non-live vaccines. These vaccines trigger a partial immune response. Genetic vaccines are non-live vaccines that trigger a full immune response.

The procedures outlined in this feature have been greatly simplified. Also, some steps are meant to show what is done but not how. For example, a gene cannot be plucked out of DNA using tweezers, and there’s no box-like device called a purifier that can extract toxins from bacteria as well as viruses from pus.

 

Similar-pathogen vaccine: smallpox virus

Step 1 Use the sterile petri dish to collect fluid from pustules on the cow’s udder.

 

To create a vaccine that will protect you against a pathogen, you usually begin with that pathogen and alter it in some way. Not so with smallpox. To create this vaccine, you begin with another virus that is similar to the smallpox virus, yet different enough not to bring on the smallpox disease once it enters your body. This similar virus is cowpox.

The cow to the left has been intentionally infected with cowpox virus. The fluid that you collect from virus-caused pustules on the cow’s udder contains many copies of the virus.

Step 2 Use the purifier to isolate the viruses.

 

Smallpox vaccines contains cowpox viruses but not the bacteria and other impurities found in the fluid collected from such pustules.

To make the vaccine, therefore, you’ll need to separate the cowpox viruses from the rest of the fluid.

Step 3 Fill the syringe with the purified cowpox viruses.

 

The smallpox vaccine is a live vaccine; the cowpox viruses it contains will invade cells in your body, multiply, and spread to other cells in your body, just as the smallpox viruses would. And as with smallpox, the body’s immune system will mount an attack against the cowpox and subsequently always “remember” what it looks like. Then, if cowpox or the similar smallpox ever enters the body, the immune system will quickly get rid of the invaders.

Done The smallpox vaccine is complete.

 

At one time, cows were used to create the smallpox vaccine. In fact, the decades-old stockpile in the U.S. today was made using live calves through a process similar to the one outlined here. Advancements in biotechnology, however, have led to more efficient procedures that make use of bioreactors.

Attenuated vaccine: measles virus

Step 1 Use the tissue culture to grow new viruses.

 

You are about to create a live-attenuated vaccine, which means that you need to alter a pathogen — in this case a measles virus — so that it will still invade cells in the body and use those cells to make many copies of itself, just as would any other live virus. The altered virus must be similar enough to the original measles virus to stimulate an immune response, but not so similar that it brings on the disease itself.

To create a new strain of the virus, you’ll need to let it grow in a tissue culture.

Step 2 Fill the syringe with a strain of the virus that has desirable characteristics.

 

The tissue culture is an artificial growth medium for the virus. You will intentionally make the environment of the culture different than that of the natural human environment. For this vaccine, you’ll keep the culture at a lower temperature.

Over time, the virus will evolve into strains that grow better in the lower temperature. Strains that grow especially well in this cooler environment are selected and allowed to evolve into new strains. These strains are more likely to have a difficult time growing in the warmer environment of the human body. After many generations, a strain is selected that grows slow enough in humans to allow the immune system to eliminate it before it spreads.

Done The measles vaccine is complete.

 

Like the smallpox vaccine, the virus within the vaccine will invade body cells, multiply within the cells, then spread to other body cells. The virus used in the measles vaccine today took almost ten years to create. The starting stock for the virus originated from a virus living in a child in 1954.

Live-attenuated vaccines are also used to protect the body against mumps, rubella, polio, and yellow fever.

 

Killed vaccine: polio virus

 

Step 1 Use the tissue culture to grow new viruses.

 

The goal in creating a killed vaccine is to disable a pathogen’s replicating ability (its ability to enter cells and multiply) while keeping intact its shape and other characteristics that will generate an immune response against the actual pathogen. When the body is exposed to the killed polio vaccine, its immune system will set up a defense that will attack any live polio viruses that it may encounter later.

To produce this vaccine, you first need many copies of the polio virus. You can grow these in a tissue culture.

Step 2 Use the purifier to isolate the polio viruses.

 

The polio virus uses the cells within the tissue culture to produce many copies of itself.

These copies of the virus need to be separated from the tissue culture.

Step 3 Use formaldehyde to kill the viruses.

 

There are several ways to inactivate a virus or bacteria for use in a vaccine. One way is to expose the pathogen to heat. This is how the bacteria in the typhoid vaccine is inactivated. Another way is to use radiation.

For the polio vaccine developed by Jonas Salk in 1954, formaldehyde was used. You’ll use formaldehyde in creating your polio vaccine, too.

Step 4 Fill the syringe with the killed polio virus.

 

The dead viruses in your polio vaccine will not produce a full immune response when injected in a body. This is true for all vaccines that are not live. For this reason, these vaccines usually require booster shots.

Done The polio vaccine is complete.

 

There are two polio vaccines widely used today. One is Salk’s killed vaccine; the other is a live-attenuated vaccine first developed by Albert Sabin.

In addition to polio and typhus, killed vaccines are used to prevent influenza, typhoid, and rabies.

Toxoid vaccine: tetanus

Step 1 Use the growth medium to grow new copies of the Clostridium tetani bacteria.

 

With a toxoid vaccine, the goal is to condition the immune system to combat not an invading virus or bacteria but rather a toxin produced by that invading virus or bacteria. The tetanus shot is such a vaccine. Tetanus is a disease caused by toxins created by the bacteria Clostridium tetani. The vaccine conditions the body’s immune system to eliminate these toxins.

To produce the vaccine, you first need to grow many copies of the Clostridium tetani bacteria.

Step 2 Isolate the toxins with the purifier.

 

While in the growth medium, the bacterial cells produce the toxin, which are toxic molecules that are often released by the cells.

To produce the vaccine, you’ll need to separate these molecules from the bacteria and the growth medium.

Step 3 Add aluminum salts to the purified toxins.

 

In this state, the toxin would be harmful to the human body. To make the vaccine, it needs to be neutralized.

Sometimes formaldehyde is used to neutralize toxins. For your vaccine, you’ll use aluminum salts to decrease its harmful effects.

Step 4 Fill the syringe with the treated toxins.

 

The toxin would work as a vaccine now, but it wouldn’t stimulate a strong immune response. To increase the response, an “adjuvant” is added to the vaccine.

For the tetanus vaccine, another vaccine acts as the adjuvant. This other vaccine inoculates against pertussis. The vaccine for diphtheria — also a toxoid vaccine — is also often added to the tetanus/pertussis combo, making for the DPT vaccine.

Done The tetanus vaccine is complete.

 

As with other inactivated vaccines, there are disadvantages with toxoid vaccines. Even with the adjuvant, these vaccines do not produce a full immune response. Booster shots are needed to maintain the immunity.

 

 

Subunit vaccine: hepatitis B

Step 1 Use the tweezers to pull out a segment of DNA from the hepatitis B virus.

 

A subunit vaccine makes use of just a small portion of a pathogen. For a virus, the vaccine can contain just a piece of the protein coat that surrounds the virus’s DNA (or RNA). Even small portion of a virus is sometimes enough to stimulate an immune response in the body.

There are several ways to produce a vaccine for hepatitis B vaccine. For your vaccine, you’ll use genetic engineering techniques.

 

Step 2 Add the segment of DNA to the DNA of a yeast cell (which is in the yeast culture).

 

A segment of the virus’s DNA is responsible for the production of the virus’s protein coat. You will add this segment to the DNA within a yeast cell.

The yeast cell, as it grows, will “read” the viral DNA incorporated in its own DNA and produce the protein that makes up the protein coat of hepatitis B.

Step 3 Use the purifier to isolate the hepatitis B antigen produced by the yeast cells.

 

The vaccine, once administered, will stimulate the immune system to attack the antigen (i.e., the protein coat). Then, if the inoculated person is later exposed to the virus, the immune system will quickly respond to the invader and eliminate it before it has a chance to spread widely.

To finish making the vaccine, you need to separate the proteins from the yeast cells.

Step 4 Fill the syringe with the purified hepatitis B antigen.

 

The isolated hepatitis B protein, produced by the yeast cells, contains none of the viral DNA that makes hepatitis B harmful. Therefore, there is no possibility of it causing the disease.

Done The hepatitis B vaccine is complete.

Another example in the subunit category is the anthrax vaccine approved in the U.S. (The countries of the former Soviet Union have an attenuated version of the vaccine.) The U.S. vaccine is currently administered to military personnel.

 

Naked-DNA vaccine: HIV

Step 1 Use the growth medium, which includes PCR primers, to make billions of copies of a single gene.

 

Genetic vaccines, sometimes called naked-DNA vaccines, are currently being developed to fight diseases such as AIDS. The goal of these vaccines is to use a gene from a pathogen to generate an immune response. A gene contains the instructions to create a protein. With a genetic vaccine, small loops of DNA in the vaccine invade body cells and incorporate themselves into the cells’ nuclei. Once there, the cells read the instructions and produce the gene’s protein.

Using a technique called PCR, which stands for polymerase chain reaction, you’ll make many copies of a specific gene. The work of finding the gene and copying sequences of its DNA is done by “primers.”

Step 2 Combine the virus genes with vectors.

 

To make your genetic vaccine, you’ll use vectors. Vectors are agents that are able to enter and instruct cells to create proteins based on the vector’s DNA code. In this case, the vectors are loops of double-stranded DNA. You can exploit the vector’s ability to create proteins by splicing a gene from the virus into a vector. The cell that the vector later invades will then produce proteins created by the virus.

The vectors and copied genes have been treated with restriction enzymes, which are agents that cut DNA sequences at known locations. The enzymes have cut open the round vectors and trimmed the ends of the copied genes.

Step 3 Add bacteria to the vectors to allow the altered vectors to replicate.

 

The ends of the vectors have again come together, but now with a gene spliced into the loop. You’ll need many copies of the vector/gene loop for your genetic vaccine. These copies can be produced with the help of bacteria.

Vectors are capable of self-replicating when within a bacterial host, as long as that host is in an environment conducive to growing. After you combine the vectors and bacteria, the vectors will be shocked into the bacteria.

Step 4 Use the purifier to separate the altered vectors from the bacteria.

 

The final vaccine should include only the vectors, so you’ll need to separate them from the bacteria after enough copies have been produced. This can be done with a detergent, which ruptures the cell walls of the bacteria and frees the DNA within.

The relatively large bacterial DNA can then be separated from the smaller DNA loop that makes up the vector.

Step 5 Fill the syringe with the altered vectors.

 

Upon inoculation, billions of copies of the altered vector will enter the body. Of these, only 1 percent will work their way into the nuclei of body cells. But that’s enough.

The body’s immune system responds to these proteins once they leave the cell. But more importantly, it also reacts to proteins that are incorporated into the cells’ walls. So in addition to mounting an attack against the free-floating proteins, the immune system attacks and eliminates cells that have been colonized by a pathogen. The vaccine, then, works like a live vaccine, but without the risk. (With a live vaccine, the pathogen can continue to replicate and destroy cells as it does so.)

Done The naked-DNA vaccine is complete.

Trials for a genetic vaccine that may protect against AIDS began in 1995. These vaccines, which contained HIV genes, were given to patients who already were infected with HIV. A year later, the trials were expanded to test people without HIV. These trials are still being conducted and have not yet produced conclusive results.

Human trials for genetic vaccines against herpes, influenza, malaria, and hepatitis B are also underway.

Note: Although the genetic material of HIV is RNA, the procedure for making the vaccine is similar.

http://www.news-medical.net/health/What-are-Vaccines.aspx

http://www.thevaccines.co.uk/gb/home/

http://www.iavi.org/Pages/home.aspx?google

http://www.vaccines.org/

http://intranet.tdmu.edu.ua/www/tables/1737.jpg

 

Prevention of Infectious Diseases

and Measures to Control Them

http://www.csc-scc.gc.ca/text/pblct/infectiousdiseases/en.pdf

http://www.health.gov.on.ca/english/providers/program/pubhealth/oph_standards/ophs/infdis.html

http://www.health.state.mn.us/divs/idepc/index.html

Prevention and control of infectious diseases include the following:

(1) mass-scale measures aimed at improvement of public health, prevention and spread of infectious diseases;

(2) medical measures aimed at reduction of infectious morbidity and eradication of some diseases;

(3) health education and involvement of population in prevention or restriction of the spread of infectious diseases;

(4) prevention of import of infectious diseases from other countries.

Improvement of peoples’ well-being, adequate housing, medical aid, and health education should be adequately planned and carried out. Preventive sanitary supervision is also necessary. Industrial objects, residential houses, children’s and medical institutions should be constructed with strict adherence to the special sanitary requirements that are intended to improve labour and living conditions, prevention of onset and spread of infectious diseases.

Preventive measures aimed to control infectious diseases taken by medical personnel are divided into preventive and anti-epidemic. Preventive measures are carried out regardless of the presence or absence of infectious diseases at a given time and locality. These measures are aimed at prevention of infectious diseases.

Anti-epidemic measures are necessary when an infectious disease develops. It has already been said that the following three basic factors are necessary for development of an epidemic: the source of infection, transmission mechanism, and susceptibility of population. Exclusion of any of these factors terminates the spread of an epidemic process. Prophylactic and antiepidemic measures are therefore aimed at control of the source of infection, disruption of the route by which infection spreads, and strengthening of non-susceptibility of population.

Control of infection source. Patients with some infectious diseases, e. g. measles, pertussis, dysentery or cholera, liberate the pathogenic microorganisms into the environment during the last days of the incubation period or during the first day of the disease. Timely revealing of the sick is thus very important. Active detection of the sick is performed by medical personnel at hospitals, polyclinics, medical posts and the like. Health education of population by medical personnel promotes early attendance of the sick for medical aid and thus helps timely detection of infectious patients. Examination of population in outpatient conditions (in residential districts) is helpful in this respect.

An infectious disease is diagnosed on the basis of clinical findings, epidemiologic anamnesis and laboratory tests. All patients with the diagnosis of an infectious disease should be entered into a special record. The record should be made by a physician or a medical nurse. All cases of infectious diseases or suspected cases should be entered into the record, and higher epidemiologic authorities should be informed not later than within 24 hours. In cases of plague, cholera or other disease that requires quarantine measures, local medical personnel must inform higher authorities of the health system.

The infectious patients must be isolated in proper time. Patients with plague, cholera, viral hepatitis, typhoid and paratyphoid fever, diphtheria, and similar contagious diseases should be immediately hospitalized. The patients should be handled in special ambulance cars that should be disinfected after transportation of each patient (See Disinfection). The patient delivered to the hospital must be given appropriate sanitary treatment before placing in the appropriate ward or an isolated room, if the diagnosis is not clear, or infection is mixed by its character. Special measures should be taken in order to prevent spread of infection within the hospital. In order to remove the danger of spreading infection, the patient should be given appropriate therapy. Patients with scarlet fever, escherichiasis, dysentery and the like diseases can remain at home where they must be isolated from the other family. The family must be instructed how to prevent infection and to disinfect the household utensils. Observation of the patient by the medical personnel must be constant.

Persons cured from infectious diseases should be discharged from hospital after alleviation of all clinical symptoms, and examination for the carrier state, specific for each particular infection; for example, person who sustained diphtheria, can be discharged from hospital after a complete clinical cure and two negative bacteriological tests of the faucial and nasopharyngeal smears. Persons who recovered from typhoid fever, paratyphoid, salmonellosis, dysentery should be observed in outpatient conditions. The term of observation depends on each particular disease.

Carriers of infection should be revealed and isolated for medical examination and treatment. Since it is impossible to screen the entire population, only those who can be a danger for the surrounding people (personnel of children’s institutions, food catering, and the like establishments) should be inspected.

If the epidemiologic situation requires, the following groups of people should be examined for the carrier state: (a) persons who can be in contact with typhoid fever patients, patients with dysentery, paratyphoid, diphtheria, and meningococcal infection; (b) persons with a history of sustained typhoid fever, paratyphoid, and dysentery; (c) persons suspected for being a source of infection in the focus of infection. The carriers must be immediately withdrawn from their occupation at food catering or children’s institutions till they are completely cured and given multiple tests for the absence of the carrier state. Chronic carriers should be moved to other jobs that are not connected with food or children. Infection carriers must be regularly treated and observed according to special instructions.

If animals are the source of infection, measures differ. Veterinary measures should be taken with respect to domestic animals. Animals with brucellosis should be slaughtered. Horses with glanders should also be killed. Food and materials obtained from diseased animals must be given special treatment. Farms where infection is revealed, must be disinfected and quarantine established. Wild animals that are not the object of quarry must be destroyed, and measures for their isolation from man should be taken.

Disruption of infection transmission pathways. The pathways by which infection can be transmitted are disrupted by acting on the transmission factors. Since intestinal infections are transmitted by the faecal-oral route, all preventive measures are aimed to preclude contact of the infected material with water, food, or hands. General sanitary measures should be taken constantly and universally, regardless of the presence or absence of infection in a given locality.

Community hygiene is very important in prevention of infection spread. Layout of settlements, housing conditions, the presence or absence of water supply and sewage systems are important factors in this respect. Permanent control of water supply system, a correct selection of water body and the site of water intake, protection of the water intake zone, purification and decontamination of water are important preventive measures. Soil protection from contamination with domestic wastes and sewage and timely cleaning of settlements are decisive measures against flies.

Almost all intestinal infections can spread by ingestion of food. The anti-epidemic role of sanitary supervision over foods consists in prevention of contamination of food during all stages of its preparation, cooking, handling and storage, and during final dressing before serving. Neglected rules of cooking and storage of food at catering establishments, shops, and in food industry result in mass-scale spreading of salmonellosis, dysentery, typhoid fever, paratyphoid, etc.

Health education of population is decisive too.

Respiratory infections are easily transmitted from the source of infection to susceptible population. The main measure is prevention of overcrowding, adequate insolation and ventilation of enclosures, use of ultraviolet radiation for disinfection of air at medical and children’s institutions. Respirators are necessary in special cases.

In blood infections, the pathogenic agent resides in the blood supply system, in the lymphatic system and sometimes in various bodily organs. The pathogenic agent is transmitted to another susceptible macroorganism through bites of the blood-sucking arthropods. Besides, inoculation is possible during transfusion of blood from an infected person, through wounds during autopsy of the infected dead, during removing skin from infected rodents with valuable fur; transmission of infection is possible during medical manipulations that can be associated with damage to the blood vessels.

Most blood infections are characterized by natural nidality, except those transmitted by lice.

Irrigation of land, drying of swamps, cultivation of new soils and other measures taken in combination with medical ones have considerably decreased morbidity of tick-borne encephalitis, tularaemia, malaria and many other infections.

Control of arthropods (disinsection) is important for prevention of blood infection. Improved living, labour and leisure conditions of population and sanitary control at hairdressers’, etc. promote eradication of recurrent fever and louse-bome typhus.

In skin infections, each particular disease is characterized by specific routes of transmission of the causative agent which depend on the living and labour conditions. The transmission mechanism Can be broken by improving general health of population and the living and labour conditions. In addition to the mentioned general «anitary conditions, disinfection is another important factor for the disruption of the transmission pathways. Measures to break the transmission mechanism during wound infections include prevention of industrial injuries, traffic and domestic trauma.

Measures to increase non-susceptibility of population. Non-susceptibility of population is increased by improving general non-specific resistance of population by improving the living and labour conditions, nutrition, physical training, health envigorating measures and by creating specific immunity through preventive vaccination. The ancients noted that people who had sustained many infectious diseases became non-susceptible to repeated infection with the same disease. In the Orient (China, India) they believed that if a person could sustain a mild form of an infection, it could protect him from dangerous diseases during epidemic outbursts. They protected themselves from smallpox by rubbing the content of smallpox lesions into the skin or ingested crusts (variolation), or put contaminated underwear of smallpox patients on healthy children, etc.

In Europe, first attempts to create artificial non-susceptibility to infectious diseases were made in the 18th century. Variolation was practiced in England, Germany, Italy, France, Russia and some other countries. Samoilovich, for example, suggested that population could be immunized by the bubonic contents of plague patients.

The discovery of the English physician Edward Jenner has become a turn point in the teaching of artificial immunity. In 1796, Jenner developed a process of producing immunity to smallpox by inoculation with cowpox vaccine.

Louis Pasteur produced a live vaccine against anthrax by attenuating the causative agents at high temperature. His principle was used successfully by other investigators who also manufactured live vaccines. Virulence of tuberculosis bacteria has thus been decreased by multiple cultivation of the starting culture on bile-potato media.

Most effective proved the method of controlled variability of microbes and selection of low-virulence and highly immunogenic strains. Artificial active immunity is now induced by vaccines (from Latin vacca, cow and vaccina, cowpox); the method is known as vaccination.

The following preparations are used to prevent infectious diseases:

live vaccines prepared from attenuated non-pathogenic microorganisms or viruses; inactivated vaccines prepared from inactive cultures of pathogenic microorganisms causing infectious diseases; chemical vaccines (antigens), isolated from microorganisms by various chemical methods; toxoids, prepared by treating toxins (the poisons produced by microorganisms causing infectious diseases) with formaldehyde.

Vaccines can produce immunity against a given infectious disease or can be polyvalent, i. e., effective against several infectious diseases. Adsorbed vaccines are popular. Aluminium hydroxide is used as an adsorbent. Adsorbed vaccines induce active durable immunity in the vaccinated macroorganism by creating a depot at the site of administration of the antigen, which is slowly absorbed.

Live vaccines are used to create specific immunity against poliomyelitis, measles, influenza, tuberculosis, brucellosis, plague, tularaemia, anthrax, Q fever, skin leishmaniasis, epidemic parotitis, and some other diseases.

Live vaccines prepared from attenuated vaccine strains of microorganisms are more effective than inactivated chemical vaccines. Immunity induced by live vaccines is about the same as produced by normal infection. Live vaccines are given in a single dose intra-cutaneously, subcutaneously, per os, into the nose or by scarification. The disadvantage of live vaccines is that they should be stored and transported at a temperature not exceeding 4-8 °С.

Inactivated vaccines are prepared from highly virulent strains with adequate antigen properties. They are used to prevent typhoid fever, paratyphoid, cholera, influenza, pertussis, tick-borne encephalitis, and some other diseases. Depending on the microorganism species, various methods are used to inactivate them. The microorganisms can be treated with formaldehyde, acetone, alcohol, merthiolate, or at high temperature. Efficacy of inactivated vaccines is lower than that of live vaccines although there are some highly effective inactivated vaccines as well. Inactivated vaccines are injected subcutaneously. Adsorbed vaccines are given intramuscularly. Inactivated vaccines are more stable in storage. They can be kept at temperatures from 2 to 10 °С.

Chemical vaccines are more active immunologically. These are specific antigens extracted chemically from microbial cells. Adsorbed chemical vaccines are used for active immunization against typhoid fever, paratyphoid and other diseases.

Toxoids are formaldehyde-treated exotoxins of the microorganisms causing diphtheria, tetanus, cholera, botulism, and other diseases. Diphtheria and tetanus toxoid is used in the adsorbed form. Toxoids are highly efficacious. When administered into a macroorganism, the vaccine induces an active immunity against a particular infection. Live vaccines produce an immunity that lasts from 6 months to 5 years. Duration of immunity produced by inactivated vaccines is from a few months to a year.

Immune sera and their active fractions (mainly immunoglobulins) induce passive immunity. Immune sera and immunoglobulins are prepared from blood of hyperimmune animals and from people who have sustained a particular disease or have been immunized otherwise. Passive immunization is used for urgent prophylaxis of people who are infected or supposed to be infected, and also for treatment of the corresponding infectious disease. The effect of immune sera and immunoglobulins lasts from 3 to 4 weeks. They are given intramuscularly.

Bacteriophages are used to prevent and treat some infectious diseases. Bacteriophages are strictly specific toward separate species and even types of.bacteria.

The preparations can be given parenterally (percutaneously, intracutaneously, subcutaneously, intramuscularly, intravenously) or enterally (per os), intranasally or by inhalation (aerosols).

When giving vaccines parenterally, it is necessary to observe sterile conditions and to adhere to the rules specified for injection of a particular vaccine. Jet injections are widely used now: the preparations are administered into the skin, subcutaneously and intramuscularly using various syringes.

When given in the liquid state or in tablets, the vaccine should be taken together with water.

Live vaccines are usually given in a single dose, while inactivated vaccines are given in two or three doses at intervals from 7 to 10 or from 30 to 45 days.

Revaccination is used to maintain immunity induced by previous vaccination. The terms of revaccination depend on a particular disease and vary from several months to 5 years. Efficacy of immunization depends largely on regularity of revaccination performed in due time with adequate doses. Quality of the vaccine, and the condition of its storage and transportation are also important.

When selecting persons for immunization, contraindications should be considered. Individual contraindications depend on the route of vaccination, the presence of concurrent diseases, the stage of recovery, previous vaccinations, and the like.

Vaccination should be performed by a physician or secondary medical personnel after thorough examination of persons to be vaccinated in order to reveal possible contraindications, the presence of allergic reactions to medicines, food, etc.

The main contraindications to prophylactic vaccination are as follows: (1) acute fever; concurrent diseases attended by fever;

(2) recently sustained infections; (3) chronic diseases such as tuberculosis, heart diseases, severe diseases of the kidneys, liver, stomach or other internal organs; (4) second half of pregnancy; (5) first nursing period; (6) allergic diseases and states (bronchial asthma, hypersensitivity to some foods, and the like).

Vaccination can induce various reactions. These can be malaise, fever, nausea, vomiting, headache and other general symptoms; a local reaction can develop: inflammation at the site of injection (hyperaemia, oedema, infiltration, regional lymphadenitis). Pathology can also develop in response to vaccination; such pathologies are regarded as postvaccination complications. They are divided into the following groups: (1) complications developing secondary to vaccination; (2) complications due to aseptic conditions of vaccination; (3) exacerbation of a pre-existing disease.

Prevention of postvaccination complications includes: strict observation of aseptic vaccination conditions, adherence to the schedule of vaccination, timely treatment of pathological states (anaemia, rickets, skin diseases, etc.), timely revealing of contraindications to vaccination, and screening out the sick or asthenic persons. All cases with severe reactions to vaccination should be reported to higher authorities. If vaccination is performed by scarification, the results are not always positive, and the vaccine must therefore be tested. The results of vaccination should be assessed at various terms, depending on a particular disease against which a person is vaccinated. The result of vaccination against, e. g. anthrax, should be assessed in 2-3 days.

Vaccination should be performed according to a predetermined plan, or for special epidemiologic indications. Planned vaccination is performed against tuberculosis, diphtheria, tetanus, pertussis, poliomyelitis, measles, epidemic parotitis, and against some other infections within the confinement of separate districts or population groups, regardless of the presence or absence of a given disease. Vaccination for special epidemiologic indications are performed in the presence of direct danger of spreading of a particular infection. Vaccination reports must be compiled and special entries made in histories.

The results of vaccination (efficacy of vaccination) are assessed by comparing morbidity rates among the vaccinated and non-vaccinated groups of population. The number of the diseased and severity of cases must be assessed (agglutination test, complement fixation test, test for allergy).

Sanitary and epidemiologic posts and stations must supervise the work of vaccination posts.

Complex prophylactic and anti-epidemic measures. In case of infectious outbreak it is necessary to take a complex of anti-epidemic measures aimed at eradication of the source of infection, disruption of the transmission mechanism, and increasing non-susceptibility of population. The main measure should be selected depending on the character of infection and a particular condition in a given area. Other measures are only secondary in importance, although their role is also great. For example, only systematic vaccination of the entire population has made it possible to eradicate smallpox all over the world. The main measure in louse-borne and recurrent typhus is control of the source of infection and eradication of pediculosis among population.

Anti-epidemic measures in the focus. The efficiency of anti-epidemic measures taken in the focus of infection depends largely on the time when the source of infection (patient) is revealed and isolated from the surrounding people.

Regardless of the character of the focus (family, community) measures should be taken toward the patient, the persons who were in contact with the diseased, and the surrounding objects. As the diseased person is revealed, the following measures should be taken:

the disease diagnosed, appropriate record made and the authorities informed, the patient hospitalized or isolated in out-patient conditions and given specific therapy.

The focus should be examined by an epidemiologist or a rural physician. The results of examination should be entered into a special chart (record). The purpose of the epidemiologic examination is to reveal the source and ways of infection transmission, to establish the boundaries of the focus, to determine the scope of disinfection and reveal contacts; a plan of immediate measures aimed to control and eradicate the focus should be made out.

Epidemiologic examination of the focus should begin with the study of morbidity at a given locality in the past (flat, hostel, institution, etc.), acquaintance with disease rate among animals and contamination of surrounding objects.

Questioning of the patient, the family and contacts helps reveal the source of infection. Questioning usually begins with asking the patient if he or she had contact with the diseased within his family, among the relatives or acquaintances. If a zoonotic focus is examined, possible contacts with the diseased people or animals must be established. Information about previous travels to other city or village, visits of relatives or acquaintances from other districts should be revealed. It is very important to establish occupation of the diseased, conditions of his labour, living and nutrition conditions.

The value of epidemiologic examination depends on the skill and form of questioning. It is recommended that the results of questioning should be recorded at the end of the talk. The physician must plan his questions beforehand.

Depending on a particular disease, the corresponding objects must be examined. For example, the source of water supply and rooms where food is cooked and stored should be examined in intestinal infections. If sewage is absent, waste receptacles should be examined. Places where refuse is collected must be examined as well. It is necessary to establish if flies were the transmitters of the infection. Cleaning of the surrounding territory must be inspected. Sanitation and hygiene of persons residing in the focus of infection should also be taken into consideration.

Material for microbiologic studies should be taken from the patient, his contacts, and, if necessary, animals and the surrounding objects (water, food, washings from equipment, various materials of animal origin, etc.).

Immunity tests, skin allergy tests, experimental inoculation of susceptible animals should be performed if necessary.

Persons who had contacts with the patient (in the family, house, institution) should undergo a thorough medical examination in order ; to reveal, as early as possible, new cases of the disease (Addition 1). The terms and , character of observation depend on a particular infection. For example, a typhoid fever focus is visited by medical personnel every day (during 25 days), the residents are questioned, examined, and their temperature taken. A viral hepatitis focus should be visited once a week (for 45 days). Stools must be examined in the focus of dysentery. If bacteria carriers, are found in the focus of infection, all contacts must be examined microbiologically to reveal possible carriers.

Workers and other personnel engaged in food catering and the like establishments (i.e., persons engaged in handling foods, their processing and cooking, maintenance of equipment used for food processing and cooking, staff of medical institutions dealing with nutrition of people, workers engaged in water supply and those responsible for storage of water), children at kindergartens and schools should be isolated for various terms depending on a particular infection. All persons who had contacts with plague or cholera patients should be isolated, observed, and given preventive treatment.

The room where the patient is kept before hospitalization should be disinfected. After taking the patient to hospital, or after his or her recovery from the disease (if the patient remained at home), the focus should be disinfected again. If the disease is transmitted by living transmitters (lice in louse-borne and recurrent fever, fleas in plague), disinsection must be carried out. Rodents must be exterminated in the focus of plague or tularaemia.

Health education of population must be carried out in the focus of infection. Medical personnel must acquaint population with the first signs of the disease, the measures that people must take if the signs of the disease develop, and preventive measures.

In order to stop the spread of infection and eradicate the focus of infection, specific preventive measures must be taken. Depending on indications, the entire population in a given region, or only separate persons who had contacts with the diseased must be vaccinated. For example, if there exists a danger of repeated cases of tularaemia, the entire population of a given area must be immunized.

http://www.oahpp.ca/services/infectious-disease-prevention-and-control.html

http://ecdc.europa.eu/en/publications/Publications/111012_Guidance_ECDC-EMCDDA.pdf

http://www.csc-scc.gc.ca/text/pblct/infectiousdiseases/en.pdf