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April 16, 1997

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

Author Affiliations

From the Ontario Ministry of Health, Toronto (Ms Troy); Field Epidemiology Training Program (Drs Ellis and Hockin and Ms Troy), Bureaus of Microbiology (Dr Peeling), and Infectious Diseases (Dr Spika), Laboratory Centre for Disease Control, Health Canada, Ottawa, Ontario; the Windsor-Essex County Health Unit, Windsor, Ontario (Ms Bennett); and the Windsor Regional Public Health Laboratory (Ms Murphy).

JAMA. 1997;277(15):1214-1218. doi:10.1001/jama.1997.03540390044033

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<.001) and sore throat (P<.001). Residents who smoked had onset of illness earlier than nonsmokers (P=.007), which perhaps is related to airborne transmission in a designated smoking room.

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.