A seven-year study of WHO virus laboratory reports on respiratory viruses.

In 1963 the World Health Organization established a system for the collection and distribution of information on viruses. By 1973 laboratories in 45 countries were participating in this scheme. The present study is an analysis of the reports on adenovirus, influenza viruses A, B, and C, parainfluenza virus, respiratory syncytial (RS) virus, rhinovirus, and Mycoplasma pneumoniae during 1967-73. In the northern hemisphere, from which over 95% of the reports were received, a clear pattern of the seasonal incidence of different respiratory tract infections emerged. Over 70% of the total number of reported adenovirus infections, over 80% of the parainfluenza virus infections, and over 90% of the RS virus infections were in children. M. pneumoniae infections were most frequently reported in adults. Influenza A virus infection was predominant in the adult population, with a high proportion in those aged 60 years and over. Influenza B infections were reported equally in adults and children, but over one third were in children of school age. The proportion of lower respiratory infections to total respiratory infections varied from one virus to another, and ranged from less than half for adenovirus to over four fifths for mycoplasma infections. Nonlocalizing fever was usually the second principal clinical condition reported in association with respiratory viruses.