Epidemiologic assessment of methods of transmission of legionellosis.

The ubiquity of Legionella pneumophila in the environment creates special problems for identifying the source of either outbreaks or sporadic cases due to this organism. Efforts must be made to associate a specific hypothesized source with the occurrence of disease through appropriate epidemiologic studies. Well documented sources of outbreaks include contaminated heat rejection devices, industrial aerosols, and recreational whirlpools. The presence of L. pneumophila in potable water supplies has been associated with the disease in several settings. The precise mechanism of aerosol generation and transmission from potable water remains to be defined.