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From June 1989 to March 1990 there were eight cases of Legionnaires' disease caused by Legionella pneumophila serogroup 1 in a renal transplant unit. There were seven cases of pneumonia and one case of pleural effusion. A study was conducted to identify the source of the outbreak. Legionella anisa was cultured from tap water. Twenty-seven staff members of the unit were serologically tested and antibody titres were positive in two. The probable source of infection was the potable water system. Control measures were hyperchlorination and heating of the water, after which there were no further cases during 5 months' follow up. We believe this is the first reported Legionnaires' disease outbreak in Latin America.

In 1 year 12 of 48 patients who developed fatal pneumonia following admission with non-respiratory disorders to the Hospital Molinette, Torino, yielded Legionella pneumophila serogroup 1 from lung at autopsy. Patients were hospitalized on seven different wards for different conditions; only two of the wards had air conditioning but legionellas were not isolated from these. All patients were in poor health or immunocompromised. Some patients had inhaled humidified oxygen from piped supplies and three had undergone surgery. Legionella pneumophila serogroup 1 was detected in the water of oxygen bubble humidifiers and an underwater chest drain. The contaminated devices had been filled with tap or distilled water and the hospital water supply was found to be contaminated with L. pneumophila serogroup 1. Our findings suggest that filling bubble humidifiers or underwater chest drains with tap water is a potential hazard and should be avoided.

We describe the first reported case of pneumonia due to Legionella pneumophila serogroup 12 in the UK. This hospital-associated infection occurred in an immuno-incompetent patient and coincided with a change in character of the local environmental strains of legionellas. The patient produced a serological response both to her own isolate and to L. pneumophila serogroups 1-6. Thus serodiagnosis was attainable using the usual screening antigens.

The installation of a valve to drain away water on the completion of showering was found to have no significant effect on the numbers of microorganisms in shower water and on the internal surfaces of shower fittings.