February 2012

What Is Legionnaires’ Disease?

Legionnaires’ disease (LEE-juh-nares) is caused by a type of bacteria called Legionella pneumophila. Legionella bacteria are found naturally in the environment, usually in water. The bacteria grow best in warm water (hot water tanks, large plumbing systems, parts of air conditioning systems of large buildings). People get Legionnaires’ disease when they breathe in air contaminated by droplets of water containing the bacteria.

What Are the Symptoms?

People with Legionnaires’ disease have symptoms similar to other types of pneumonia. These include high fever, chills, cough, muscle aches and headaches.

How Soon Do Symptoms Appear?

Symptoms usually begin 5 to 6 days after being exposed to the bacteria but can occur as early as 2 or as late as 14 days after exposure.

How Do I Know I Have Legionnaire’s Disease?

Laboratory tests are available to detect Legionnaires’ disease in those suspected of having this infection.

How Serious Is It? Who Is at Risk?

Persons 65 years and older are most at risk for Legionnaires’ disease. Smokers, those who have chronic lung disease or weak immune systems (diabetes, cancer, transplant patients) are also at higher risk. Even with treatment, Legionnaires’ disease can be fatal in up to 5-30% of people with pre-existing severe medical problems.

How Is Legionella Spread?

Legionella bacteria are NOT spread from one person to another person. To get infected, you must breathe air contaminated by droplets from a source of Legionella bacteria. A person diagnosed with Legionnaires’ disease in the community or the workplace is not a threat to others who share common space.

How Is Legionnaires’ Disease Treated?

Most cases can be treated successfully with antibiotics. Healthy people usually recover from the infection. Older people and those with other serious, pre-existing health problems are not able to fight the infection as effectively and often take longer to recover, even with timely and appropriate treatment.

Outbreaks of Legionnaires’ disease

Outbreaks occur when two or more people become ill in the same place at the same time. When groups of people exposed to the same environmental source get pneumonia, doctors think about Legionnaires’ disease.

In the past decade, there have been several outbreaks in hospitals, hotels, factories, nursing homes and older buildings. Sources of outbreaks have been linked to atmospheric cooling towers, hot water systems and hydro-massage tubs.

If you are involved in the maintenance, ownership, or day-to-day operation of cooling towers or a hot water system, visit the following sites for more information on what you can do to prevent the growth and spread of Legionella bacteria:

  • Cooling towers
  • Hot water systems (i.e. spa and/or hydro massage tubs)

What is Pontiac Fever?

Pontiac Fever is a mild form of illness caused by the same bacteria, Legionella pneumophila that causes Legionnaires’ disease. Symptoms include fever and malaise but illness does not progress to pneumonia. Pontiac Fever usually lasts 2 to 5 days and does not require treatment.

What Should I Do If I Think I Was Exposed to Legionella Bacteria?

Most people exposed to the bacteria do not become ill. If you have reason to believe you were exposed to the bacteria that causes Legionnaires’ disease, talk to your doctor and call Toronto Public Health at 416-338-7600 (TTY at 416-392-0658).