[Nosocomial Legionnaires' disease--results from the analysis of Germany's surveillance data; 2004-2006]

Legionella bacteria colonize drinking water systems and can cause severe pneumonia in humans (Legionnaires' disease (LD)). The German network for community-acquired pneumonia (CAPNETZ) estimates 15,000-30,000 new cases of LD per year in Germany. LD cases are divided into those that were acquired in the context of a stay in a hospital or nursing home (healthcare-associated; HCA), in the community (community-acquired (CA)) or during travel (travelassociated (TA)). According to the recommendations of the Communicable Disease Surveillance Centre (CDSC; UK) and the Healthcare Infection Control Practices Advisory Committee (HICPAC; USA) a single case of nosocomial LD should prompt an epidemiologic and, depending on its results, also technical investigation of the institution. In this study we present data from nosocomial cases of LD in the context of all cases of LD that were reported to the Robert Koch Institute (RKI) within the mandatory surveillance system from 2004 through 2006. We calculated the number of cases per population (incidence), the number of cases per person-days at risk (incidence rate) and case fatality. The analysis comprised 1,339 cases of LD. Among the 942 cases with one of the three categories of exposure CALD was reported in 58 % (547 cases), TALD in 29 % (270 cases) and HCA-LD in 13 % (125 cases). The incidence rate of TALD was 9-fold, but that of HCA-LD 15-fold higher than that of CALD. Case fatality of HCA-LD was 13 % and thus higher than that of CALD (9 %) and TALD (5 %). HCA-LD cases were reported from all states and included 77 different counties. Reporting counties represent the place of residence of the LD case-patients. German notification data show that cases of LD, and likely also HCALD, are underreported. Incidence rate and case fatality are highest in HCA-LD. HCA-LD occurs widespread. These results and the preventability of HCA-LD support the recommendation to thoroughly investigate single cases of HCA-LD in hospitals and nursing homes.