Legionnaires’ disease (legionellosis) is an infection caused by
the bacterium Legionella pneumophila.
It was first identified in 1976 after many attendees at an American Legion
convention in Philadelphia suffered from pneumonia. The bacteria are found
naturally in the environment, generally in warm water. Because the bacteria grow best in warm
water, they have also been found in cooling towers, hot tubs, hot water tanks,
large plumbing systems and decorative fountains.
People become sick when they breathe in contaminated water
droplets through mist or vapors. Most people with legionellosis have pneumonia
and some will require hospitalization. Others will have more severe
complications and some will die from the infection. The Legionella bacteria can also cause Pontiac Fever, which is a milder
form of legionellosis and does not cause pneumonia. Pontiac Fever will go away
on its own after about 2-5 days and does not require treatment with
antibiotics. People who are infected with Legionella
bacteria can not spread it to other people; it is not contagious.
People most at risk from illness due to legionellosis are those
aged 65 years or older, current and former smokers, those who are
immunosuppressed or taking drugs to suppress the immune system, and people with
chronic lung disease.
On average, between 8,000 and 18,000 people are hospitalized in
the U.S. and 51 are diagnosed with Legionnaire’s disease in Connecticut
annually. Many infections are not diagnosed or reported so these numbers may be
higher. Summer and early fall are generally the times when more cases are seen;
however, infection can happen during any season.
Outbreaks happen when two or more people become sick at the same
time in the same place. This generally happens in buildings with complex water
systems. Outbreaks have also been associated with whirlpool spas, cruise chips,
and water used for drinking and bathing.
Legionnaires’ disease can be prevented by thorough cleaning of cooling
towers according to guidelines and other warm water holding containers according
to the manufacturer’s instructions.
To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.