Chlamydia pneumoniae as a New Source of Infectious Outbreaks in Nursing Homes

Objective. —To determine the extent and severity of illness and mode of transmission of Chlamydia pneumoniae infection in 3 nursing home outbreaks. Design and Setting. —Retrospective cohort study in 3 nursing homes in Ontario from September to November 1994. Subjects. —A total of 549 residents and 65 staff members. Main Outcome Measures. —Morbidity and mortality were determined by a review of disease surveillance forms, residents' charts, and a self-administered questionnaire to staff. Single and paired serum samples for C pneumoniae serological testing and nasopharyngeal swabs for Cpneumoniae culture were collected, and direct fluorescent antibody assays were performed to confirm C pneumoniae infection. Results. —The attack rates for confirmed and suspected cases combined were 68%, 46%, and 44% among residents in nursing homes A, B, and C, respectively, and 34% among nursing home C staff. A total of 16 cases of pneumonia confirmed by chest x-ray and 6 deaths were identified. The spectrum of illness among nursing home C residents included a new cough in 58 (100%), fever in 37 (64%), sore throat in 14 (24%), and hoarseness in 8 (14%). Staff members at nursing home C were more likely to report hoarseness (P Conclusions. — Chlamydia pneumoniae caused serious morbidity and mortality among residents and morbidity among staff; Cpneumoniae is an important cause of respiratory disease outbreaks in nursing homes, and diagnostic tests must be readily available for early recognition of C pneumoniae infections.