[Aetiological studies on viral pneumonia (author's transl)].

401 cases of viral pneumonia diagnosed between January 1973 and August 1975 were investigated serologically by the complement-fixation test. The percentage distribution of the responsible pathogenic organism in this series of cases was as follows: influenza virus A 45.9%, Mycoplasma pneumoniae 19.5%, Coxsackie B viruses 9.2%, cytomegalovirus 7.5% and Chlamydia psittaci 8.5%. The remaining 9.4% cases were caused by adeno, parainfluenza, measles, influenza B, herpes simplex and respiratory syncytial viruses. Influenza virus was found mainly in elderly people (mean age 58.4 years), whilst pneumonia due to Mycoplasma occurred mainly in young adults (mean age 24.4 years). Infections with Coxsackie B viruses were almost entirely restriced to the warmer months; by contrast, the influenza virus was usually found in epidemic form and only during a few weeks in winter.