Possible nosocomial transmission of psittacosis.

OBJECTIVES: To investigate a cluster of seven pneumonia cases among persons exposed to a pet-shop worker hospitalized with psittacosis.

DESIGN: Epidemiological study of the outbreak, sero-diagnostic evaluation of exposed persons with pneumonia; and retrospective review of the pneumonia cases.

SETTING: 450-bed teaching community hospital.

PARTICIPANTS: Employees of the nursing unit where the patient with psittacosis was hospitalized.

RESULTS: The index case had laboratory and clinical evidence of psittacosis. Four of the seven exposed persons who developed pneumonia had serologic results that met criteria for a diagnosis of psittacosis, and three met criteria for Chlamydia pneumoniae infection, possibly reflecting cross-reactivity between the microimmunofluorescence assays for the two diseases. The epidemiological graph suggested a relationship between the index case and the cluster of pneumonias in exposed individuals.

CONCLUSIONS: Psittacosis may have been transmitted person to person in a hospital setting.