Legionnaires' disease

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Definition

In July 1976, thousands of American Legionnaires gathered to celebrate the American bicentennial. Within a few weeks, hundreds of them were seriously ill and 34 had died. All had symptoms of severe pneumonia, some with fevers topping 107 F. It took nearly six months to identify the cause of the illness, a bacterium that causes lung infection and which became known as Legionnaires' disease.

Since then, sporadic outbreaks of Legionnaires' disease have occurred around the world — in hospitals and nursing homes, hotels, prisons, on cruise ships and even at garden shows. The common denominator is water and occasionally soil contaminated with the bacteria that cause the disease. Most often, people develop Legionnaires' disease after they inhale bacteria now called legionella, which flourish in large air conditioning systems, showers, whirlpool spas and in some cases, potting soil. It's not entirely clear why some people exposed to the bacteria become sick and others don't, although older adults, smokers and people with weakened immune systems are especially vulnerable.

The same bacteria that cause Legionnaires' disease also cause Pontiac fever, a much milder illness resembling the flu. Separately or together, the two illnesses are sometimes called legionellosis. Pontiac fever usually clears on its own in a few days with no lasting effects, but untreated Legionnaires' disease is sometimes fatal. Although prompt treatment with antibiotics can usually cure Legionnaires' disease, some people continue to experience problems even after treatment.

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Symptoms