[Legionella in Trondheim, Norway--determining sources of contagion and tracing risk environments]

Legionnaires' disease, most often a serious condition, is a relatively rare disease in Norway although in recent years it has been on the increase. Because of clinical and microbiological diagnostic difficulties, one can assume that the number of new cases reported is significantly too low.

A multidisciplinary team established in the City of Trondheim has two main functions; first, to trace sources of contagion when outbreaks of the disease and detected; second, to carry out routine inspections in order to trace potential environmental sources.

Over a four-year period (2001 - 2004), 19 cases of Legionnaires' disease were diagnosed; 17 of these are presumed to have originated locally. This is an incidence rate five times greater than the national average. Legionella pneumophila was discovered in the patients' local environment in 6 cases. Environmental investigations showed that the bacterium was present in three water-cooling towers, one Jacuzzi, one swimming pool, a shower in a factory, and in the hot-water system of a building complex. Most of the discoveries were made in the summer or autumn in several different locations in the city. Legionella pneumophila was found more often with low rather than high bacterial count, contrary to the information given in the Norwegian Legionnaires' disease prevention handbook.

Legionella pneumophila is in all likelihood a naturally occurring bacterium in many of the water sources and water supply plants in Trondheim. This requires continual awareness and readiness to tackle the disease. We have seen that a multidisciplinary team is well suited to evaluating high-risk environments, tracing outbreaks and carrying out information tasks targeted both at professionals and the public at large.