Infections with Chlamydia pneumoniae strain TWAR.

Chlamydia pneumoniae has recently been recognized as an important cause of respiratory tract disease, including atypical pneumonia. Serosurveys suggest that C. pneumoniae is endemic in most countries and is capable of causing outbreaks and epidemics of pneumonia, especially in countries where the antibody prevalence is relatively low. The population incidence of infection appears to be cyclical, with approximately 4-year cycles in the US (Seattle) and 6-year cycles in Denmark having been demonstrated. Pneumonia caused by the organism is unusual in young children in developed countries but may be an important cause of lower respiratory infections among children in developing and tropical countries. In otherwise healthy adults, C. pneumoniae pneumonia usually can be treated effectively on an outpatient basis. Patients with C. pneumoniae pneumonia often have a gradual onset of symptoms: a sore throat and hoarseness followed by a cough. Auscultatory and radiographic findings usually are prominent, even in patients with mild disease, and a cough and malaise may persist for several weeks or more after appropriate therapy. Microimmunofluorescence serologic testing is available in only a few laboratories. However, the new HL cell line holds promise of making culture and isolation of C. pneumoniae more widely available. Questions remain about the routes of transmission of C. pneumoniae, its incubation period, its role in lower respiratory disease in children in developing countries, the optimal antibiotic therapy, the existence and importance of chronic and latent C. pneumoniae infections, and the organism's association with nonrespiratory tract disease.