[Community outbreak of pneumonia due to Legionella pneumophila: importance of monitoring hospital cooling towers]

Abstract

Objective: Description of an outbreak of legionnaires' disease originating in one of the cooling towers of a hospital.

Patients and methods: This study included patients with confirmed pneumonia caused by Legionella pneumophila serogroup 1 and related to the Vallcarca neighborhood of Barcelona (Spain) in August 2004. Exposure was determined by a standardized questionnaire. An environmental investigation was carried out to identify the source of the outbreak. A descriptive analysis including incidence rates estimation was performed, as well as molecular study to document the genetic identity among human and environmental strains.

Results: Thirty-three cases of L. pneumophila pneumonia were detected. Median age was 68 years and 70% of the affected patients were men. Incidence rate among residents in less than 200 meters of the source and older than 65 was 888.9 cases/100,000 inhabitants. Lethality rate was 6%. Four seasonal cooling towers that were not registered with the authorities were identified in a health care center. L. pneumophila was isolated from all four and at least one colony in each tower had the same genetic profile as the strains isolated from patients.

Conclusions: An association was demonstrated between a community outbreak of legionellosis and unregistered seasonal cooling towers located in a hospital. All risk facilities should be registered and inspected to ensure that they fulfill current legislation requirements.