Learn About Legionnaires’ Disease

Key Facts: 

• Legionnaires’ disease is generally not spread from person to person. People get sick when breathing contaminated water mist. 

• Early diagnosis and treatment are vital to preventing life-threatening complications. 
• Most healthy people exposed to Legionnaires’ disease will not get sick, and most healthy people who do get sick will require hospital care but will recover fully with treatment.

Who Is at Risk of Legionnaires’ Disease?

Most healthy individuals exposed to Legionella will not develop Legionnaires’ disease. Certain groups of individuals, including adults over the age of 50, people currently using tobacco products or who have a history of tobacco use and people who are immunocompromised are particularly susceptible to the disease after exposure. 

Having chronic lung disease, such as COPD, emphysema, asthma, pulmonary fibrosis, cancer, diabetes, or having kidney or liver failure can also put you at an increased risk of developing Legionnaires’ disease.

What Causes Legionnaires’ Disease?

While Legionella pneumophila is responsible for most cases of Legionnaire’s disease, there are over 60 kinds of Legionella.  Many types live in the natural environment and rarely cause harm. When the bacteria contaminate man-made water systems, the risk of infection increases.

Legionnaire’s disease was named after an outbreak was discovered in the hotel where the 1976 America Legion convention was held in Philadelphia. The bacteria, the type of which was unknown at the time, were found in the hotel’s air conditioning system and later named Legionella pneumophila.

The naturally occurring bacteria can become a health concern when water is held in improperly maintained human-made structures and systems. In these instances, the bacteria multiply, causing abnormally large amounts of Legionella to concentrate. The bacteria thrive in warm water and have been found in shower heads, faucets, humidifiers, hot tubs, decorative fountains and cooling towers. The warm water can become a mist that, when breathed into the lungs, introduces bacteria from the contaminated water into lung tissue. While infections can happen in single family homes, most outbreaks are linked to large buildings.

Rarely, Legionnaires’ disease can be contracted by aspiration while drinking contaminated water. This most frequently occurs through choking or coughing, which allows liquid to enter the lungs.

What is Pontiac Fever?

Your healthcare provider may determine that you have contracted a less severe version of the same disease called Pontiac fever. This milder condition means you have been exposed to Legionella but you do not have pneumonia. Your infection should clear up on its own without treatment and cause no lingering problems. You are most likely to be diagnosed with Pontiac fever if there has been an outbreak of Legionnaires' disease and you are being screened due to potential exposure to the bacteria.