Legionnaires’ disease (legionellosis) is an infection caused by the bacterium Legionella pneumophila that was first identified following a 1976 outbreak of pneumonia at an American Legion Convention in Philadelphia. Legionella bacteria thrive in warm, aquatic environments and are relatively resistant to the effects of chlorine and heat. Legionellae are generally spread through the air by aerosolized water, which is then inhaled. Contaminated aerosols come from devices such as cooling towers, showers, and faucets. Infection has also occurred by contamination of surgical wounds with potable water. It is not transmitted from person to person. Signs of the disease can include a high fever, chills, and a cough. Some people also suffer from muscle aches and headaches. Gastrointestinal symptoms occur in 20 to 40 percent of cases.
A milder infection caused by the same type of Legionella bacteria is called Pontiac Fever. Symptoms are similar to Legionnaires’ disease with fever, headache, and muscle aches; however, there is no pneumonia.
Each year between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in the United States. Although Legionnaires’ disease can occur at any time of year, the greatest number of illnesses are usually found in the summer and early fall.
People most at risk of getting sick from infection with Legionella bacteria are older people (usually 65 years of age or older), people who smoke and those who have a chronic lung disease (like emphysema). People who have weak immune systems from diseases like cancer, diabetes, or kidney failure are also more likely to get sick when exposed to Legionella bacteria. People who take drugs that weaken the immune system (like after a transplant operation or chemotherapy) are also at higher risk.
Refer to the links below for more information about Legionnaires’ disease.
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