[Outbreak of Legionnaires' disease in a private apartment building].

BACKGROUND

An outbreak of legionnaires disease occurred in Zaragoza (Spain) in an uncommon environment such as a private apartment building was studied.

METHODS

The investigation began upon notification of 3 patients admitted with pneumonia, living in the same apartment building. The suggestion of a common source of infection led to an active search for cases and a micro-environmental study of the zone where the patients lived, as well as a follow up study of other cases with hospital acquired pneumonia throughout the city.

RESULTS

Six cases were detected over 9 days with a rate of 1.54%. The evolution of all the cases was favorable. The causal agent was serologically identified as Legionella pneumophilia serogroup 1 which was also found in the shower of one of the patient's bath with further confirmation that the strain isolated belonged to the Pontiac subgroup.

CONCLUSIONS

The probable source of infection was the potable water. The stagnation, low temperature of the boiler and the under-chlorination of the water are factors which may have contributed to the appearance of this outbreak. The control of this type of outbreak must be based on a specific information system which treats this disease as requiring individualized declaration.