RNA-viruses. Polyovirus, Coxsackie and ЕСНО viruses. Rhinoviruses. Aphthovirus and enterovirus lesions in the mouth cavity. Orthomyxoviruses. Influenza viruses. Laboratory diagnosis of flu and prophylaxis. Paramyxoviruses. Measles and Epidemic Parotitis Viruses. Respiratory syncytial virus. Laboratory diagnosis and prophylaxis of these diseases Picornaviruses are small (20-30 nm) and nonenveloped