Legionnaires’ Disease

What is Legionnaires’ Disease?

Legionnaire’s Disease is a form of atypical pneumonia caused by Legionella bacteria. It is normally spread by breathing in mist that contains the bacteria. The bacterium can be found naturally in fresh water but can also contaminate hot water tanks, hot tubs, and the cooling towers of large air conditioners.

Legionnaire’s disease is hard to diagnose because it shares signs and symptoms with other conditions like Pontiac fever which goes away without the need of treatment. The disease is named after the outbreak where it was first identified, the 1976 American Legion convention in Philadelphia. Most people who become exposed don’t become infected and it’s not typically transmitted from person to person.

Individuals at greater risk for contracting Legionnaire’s disease include older people, those with a history of lung disease, and those with poor immune function. It’s important to note that the disease can be fatal. Around 10% of those infected die. Every year in the United States eight to eighteen thousand people are hospitalized because of Legionnaire’s disease.

What are the Symptoms of Legionnaires’ Disease?

Legionnaires’ Disease can cause a cough, high fever, shortness of breath, headaches, muscle pains, vomiting, nausea, tiredness, loss of appetite, coughing up blood, and diarrhea.

Symptoms usually occur two to ten days after being exposed.

Legionnaires’ Disease Causes

Legionnaire’s disease is caused by a bacteria called Legionella which is contracted by humans when they breathe it in via water droplets. The bacteria thrives in freshwater environments and commonly affects lakes and streams. However, when it contaminates man-made water systems it tends to become a major health risk because it can then easily spread to humans.

In order to contract Legionella, you must breathe droplets of contaminated water. This could happen if, for example, a hot water tank becomes contaminated, and you have a shower which runs water from that tank. Cooling towers, pools, water features and fountains and large plumbing systems are all places where Legionnaire’s disease could originate.

Hot tubs pose a particularly high risk of Legionella contamination because they are sources of standing fresh water which is constantly kept warm, a temperature which is perfect for the growth of the bacteria. Furthermore, this warm temperature tends make chlorine and other chemicals designed to kill bacteria less effective.

Legionella cannot be contracted when it is ingested. This means that if contaminated water is drunk, it won’t infect someone unless it is accidentally breathed in and enters the windpipe instead of the digestive tract.

How is Legionnaires’ Disease Treated?

Most cases respond well to antibiotics such as fluoroquinolones, azithromycin, or doxycycline. Mild cases can be treated in an outpatient setting but some people still require hospitalization.

After a two-week cycle with antibiotics, patients need to go through close follow-up screening to make sure that all the symptoms have disappeared and that the bacteria have been completely eliminated.

Legionnaires’ Disease Prevention

Legionnaire’s disease can be prevented by keeping water systems and sources of fresh water meticulously clean, and preventing water from becoming stagnant. People with pools and hot tubs should use appropriate products to control bacteria growth, and follow recommendations from the manufacturer in regards to draining, cleaning and refilling the water.

Not everyone who contracts Legionella will get become sick. Those who smoke are at a particularly high risk of developing Legionnaire’s disease because smoking damages the lungs and makes the body more susceptible to infection. By quitting smoking, you can reduce your risk of Legionnaire’s disease.

Last Reviewed:
September 21, 2016
Last Updated:
March 12, 2018