Study of antibodies against viruses, chlamydiae, rickettsiae and Mycoplasma pneumoniae in children with respiratory diseases.

Seroconversion to different viral, chlamydial, rickettsial and mycoplasma antigens was followed up in 134 children aged 0-6 years, hospitalized with different respiratory diseases. Parainfluenza viruses type 1, 2 and 3 and adenoviruses appeared to be involved in the etiology of most of the cases; respiratory syncytial virus was often found to play a role in pneumonia/bronchopneumonia and in "influenza-like illness", while chlamydiae and M. pneumoniae could be incriminated in cases of "influenza-like illness", as well as in the other categories of respiratory disease. Mixed infections with the agents studied could be detected.