Legionellosis - Epidemiology

Epidemiology

There are about 8,000 to 18,000 cases of Legionnaires’ disease each year in the United States, according to the Bureau of Communicable Disease Control. Much has been learned about the epidemiology of Legionnaires' disease since the organism was first identified in 1976. National surveillance systems and research studies were established early, and in recent years improved ascertainment and changes in clinical methods of diagnosis have contributed to an upsurge in reported cases in many countries. Environmental studies continue to identify novel sources of infection, leading to regular revisions of guidelines and regulations. Between 1995 and 2005 over 32,000 cases of Legionnaires' disease and more than 600 outbreaks were reported to the European Working Group for Legionella Infections (EWGLI). In the future, there may be an increase in cases as the population becomes more elderly. There is a shortage of data on Legionella in developing countries and it is likely that Legionella-related illness is underdiagnosed worldwide. Improvements in diagnosis and surveillance in developing countries would be expected to reveal far higher levels of morbidity and mortality than are currently recognised. Similarly, improved diagnosis of human illness related to legionella species and serogroups other than Legionella pneumophila would improve knowledge about their incidence and spread.