Periodically, Legionnaires disease is reported to the Bureau of Epidemiology. The illness, legionellosis, is caused by the bacterium legionella pneumophila. The bacterium can cause two forms of illness: the more serious Legionnaires disease and Pontiac fever, a milder illness. The name, Legionnaires disease was assigned in 1976 when an outbreak of pneumonia occurred among attendees to an American Legion Convention in Philadelphia. Outbreaks of legionella receive significant media attention. However, most occur as a single isolated case and often without a recognized source of infection.

Legionellosis is not transmitted person to person, rather from mists that may be inhaled that come from a water source, such as air conditioning cooling towers, whirlpool spas and showers contaminated with the legionella bacteria. People of any age can acquire the illness, but it occurs more commonly in middle-aged and elderly people. Smokers, people with chronic lung disease and immune compromised individuals are at increased risk for the illness. Specific tests are performed for confirmation of the illness. Symptoms include fever, chills and a cough, which may be dry or productive, and the person often has pneumonia.

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