Virological and Epidemiological Investigations on Parainfluenza Virus Infections

Parainfluenza virus infections in Tokyo and Yokohama areas in 1959 to 1968 were investigated virologically and epidemiologically.Throat swabs of pediatric cases suffered from acute undifferentiated febrile illnesses were submitted to the virological examinations, and 184 parainfluenza viruses were isolated and identified. All types of the virus, type 1, 2, 3, 4A and 4B were detected in this decade.Epidemics of type 1 virus occurred in several primary schools, and outbreaks due to type 1, 2, 3 and 4A viruses succesively occurred in an orphanage.Though type 1 and 2 viruses were predominant in fall and winter, type 3 viruses were frequently isolated in May to July.Most of these cases from whom the viruses were isolated had upper respiratory symptoms, and only 14 cases showed characteristic syndrome of croup.