Communicable Disease Prevention and Control

Respiratory Diseases

Legionellosis

Legionellosis is an infection caused by the bacterium Legionella pneumophila. The disease has two distinct forms:

• Legionnaires' disease, the more severe form of infection that includes pneumonia, and
• Pontiac fever, a milder illness.

Outbreaks of legionellosis have occurred after people have breathed mists that come from a water source (e.g., air conditioning cooling towers, whirlpool spas, showers) contaminated with Legionella bacteria. Individuals may be exposed to these mists in their homes, workplaces, hospitals, or public places. Legionellosis is not passed from person to person, and there is no evidence of anyone becoming infected from car air conditioners or household window air-conditioning units.
 

Who can get Legionellosis?

People of any age may get Legionnaires' disease, but the illness most often affects middle-aged and older people, particularly those who smoke cigarettes or have chronic lung disease. Also at increased risk are those whose immune system is suppressed by diseases such as cancer, kidney failure requiring dialysis, diabetes, or AIDS. People who take drugs that suppress the immune system are also at higher risk.

Pontiac fever most commonly occurs in persons who are otherwise healthy.
 

What are the symptoms?

Symptoms of Legionnaires’ disease may include:

• Fever
• Chills
• Dry cough
• Muscle aches
• Headache
• Loss of appetite
• Diarrhea
• Pneumonia

Symptoms of Pontiac fever may include all of the symptoms above except for pneumonia.
 

What is the treatment?

Antibiotics are prescribed for people with Legionnaires’ disease, and hospitalization is often required. People with Pontiac fever usually recover without treatment in 2 to 5 days.