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.