Outbreak of legionnaires' disease from a cooling water system in a power station.

In September and October 1981 six cases of pneumonia occurred among men working in a power station under construction. Three were identified as cases of legionella pneumonia and two others had serology suggestive of legionella infection. In a sample of 92 men from the site 10 had low levels of antibodies to legionella; a similar sample of men working on an adjacent site showed none with positive serology. In a case control study it was found that cases of pneumonia were more likely than controls to have worked on a part of the site where four small capacity cooling towers were located. Legionella pneumophila serogroup 1 was isolated from the water systems of these four towers but was not found in samples from any other cooling towers or hot or cold water outlets on the site. It would appear that there was airborne spread of the organism from these cooling water systems which had not received conventional treatment to inhibit corrosion and organic growth. This is the first outbreak of legionnaires' disease to be recorded in an industrial setting in the United Kingdom. No cases of legionella infection have occurred on the site since the introduction of control measures.

Epidemic legionellosis in England and Wales 1979--1982.

National surveillance of legionnaires' disease in England and Wales identified 588 cases during the years 1979--1982. The majority of cases appeared to be sporadic but 32 clusters of two or more cases were recognised, 24 in association with hotels, seven with hospitals and one with a construction site. Reports (3 published and 3 unpublished) on the investigation and control of six outbreaks are reviewed. All six were found to be common source outbreaks; four hotel associated, one was nosocomial and one was associated with a construction site. Domestic water systems were implicated as sources in the four hotels and the hospital. The most effective control measure was found to be continuous chlorination of the water supply combined with raising the hot water temperature to 60 degrees C or more in the calorifier and at least 55 degrees C to a maximum of 60 degrees C at outlets. Raising hot water temperatures alone was not always completely successful as a control measure. Only in the construction site outbreak was a cooling water system shown to be the principal source of infection.