Chlamydia pneumoniae as a new source of infectious outbreaks in nursing homes

JAMA. 1997 Apr 16;277(15):1214-8.


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 C pneumoniae 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; C pneumoniae 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.

MeSH terms

  • Aged
  • Chlamydia Infections / diagnosis
  • Chlamydia Infections / epidemiology*
  • Chlamydia Infections / physiopathology
  • Chlamydia Infections / transmission
  • Chlamydophila pneumoniae* / isolation & purification
  • Cohort Studies
  • Cross Infection / diagnosis
  • Cross Infection / epidemiology*
  • Cross Infection / physiopathology
  • Cross Infection / transmission
  • Female
  • Fluorescent Antibody Technique, Direct
  • Homes for the Aged / statistics & numerical data*
  • Humans
  • Male
  • Nasopharynx / microbiology
  • Nursing Homes / statistics & numerical data*
  • Ontario / epidemiology
  • Retrospective Studies
  • Serologic Tests
  • Severity of Illness Index