Epidemics of pneumonia caused by TWAR, a new Chlamydia organism, in military trainees in Finland.

Four epidemics of pneumonia in military trainees in Finland have been shown, by microimmunofluorescence serology, to have been caused by TWAR, a recently described, unique Chlamydia organism. The epidemics occurred in four different garrisons from 1957 to 1985. Each lasted approximately six months, and epidemics occurred during all seasons of the year. The attack rate varied from 60 to 80 per 1000 men. Routine laboratory tests for respiratory agents suggested that these epidemics represented the only clusters of patients since 1970 who were positive for antibody to Chlamydia by complement fixation. From these epidemics, 62 of 70 paired sera that were positive for Chlamydia had antibody diagnostic of recent TWAR infection. Although the conscripts with pneumonia were hospitalized, the illnesses were relatively mild, and none were life threatening. Three conscripts had two episodes of TWAR pneumonia separated by three weeks to three months. Prompt treatment with tetracycline depressed the antibody response.