Epidemiological features of Legionnaires' disease in the Paris area.

Although the first French case of Legionnaires' disease (LD) was diagnosed in 1979 and the first six serogroups of L. pneumophila and L. longbeachae serogroup 2 were demonstrated in environmental samples from the Paris area, the incidence of the disease has not yet been evaluated in France. Prevalence of antibodies, as detected by an immunofluorescent assay, in the Paris population of our study ranged from 0.9 to 2.2%. LD was demonstrated in 155 (4.4%) of 3502 patients investigated mainly by serology. In a prospective study in a respiratory intensive care unit 20 (7.8%) cases of pneumonia out of 257 were caused by L. pneumophila. 171 of the 175 cases of LD diagnosed in Paris during 33 months were caused by L. pneumophila serogroup 1. Risk factors and epidemiological features of patients are similar to those described in other countries.