The infection with parainfluenza viruses is air-borne from man-to-man. Various species of animals may serve as virus reservoir. Parainfluenza viruses are endemically spread worldwide. The seroprevalence of parainfluenza in infants in their first year of life is 50%. Typical for parainfluenza viruses are frequent reinfections, this applies particularly to parainfluenza 3 viruses. lt is differentiated between parainfluenza 1, 2, 3 and 4. Together with the respiratory syncytial viruses (RS viruses), the pathogens belong to the major viral pathogens of diseases of the respiratory tract, accompanied by severe symptoms. In adults, parainfluenza virus causes a feverish rhinitis and laryngitis. First signs are sudden headaches, pain in muscles and joints, followed by fever of 38°-39°C. If the lower respiratory tract is involved, additionally trachyphonea and dry cough develops as a sign of tracheobronchitis. Parainfluenza 1 causes severe pneumonias in newborns, manifested by high fever, cyanosis, dyspnoea and bloody purulent sputum. Sometimes. meningitis symptoms occur at the same time