History & Disease Patterns
Legionnaires' disease (LEE-juh-nares) is caused by a type of bacteria called Legionella.
The bacterium got its name after a 1976 outbreak, when many people who went to a Philadelphia convention of the American Legion suffered from this disease, a type of pneumonia (lung infection). Although this type of bacterium was around before 1976, more illness from Legionnaires' disease is being detected now.
The pictured magazine covers feature the work of public health professionals in 1976 as they raced to trace the origin of the first documented outbreak of Legionnaires’ disease in Philadelphia, Pennsylvania (1).
Each year, between 8,000 and 18,000 people are hospitalized with Legionnaires' disease in the U.S. However, many infections are not diagnosed or reported, so this number may be higher. More illness is usually found in the summer and early fall, but it can happen any time of year.
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