Sorry, you need to enable JavaScript to visit this website.


DC Health

DC Agency Top Menu

-A +A
Bookmark and Share

Legionellosis (Legionnaires’ disease and Pontiac fever)

What is Legionellosis?

The term legionellosis refers to two different forms of disease: Legionnaires’ disease and Pontiac fever. Legionnaires’ disease and Pontiac fever are both caused by exposure to Legionella bacteria. You can be exposed to Legionella bacteria if you breathe in small droplets of water in the air that contain Legionella. Less commonly, you can be exposed if you drink water containing Legionella and the water “goes down the wrong pipe” and enters your lungs. Legionella is not spread from person to person.

Legionnaires’ disease is a severe form of pneumonia, while Pontiac fever is a mild form of Legionnaires’ disease and does not include pneumonia.


In 1976 individuals who attended the American Legion convention in Philadelphia developed a type of pneumonia that later became known as Legionnaires’ disease. This convention is known as the first outbreak of Legionnaires’ disease.

How does Legionellosis spread?

The bacteria Legionella is found naturally in the environment, for example in freshwater lakes and rivers. If Legionella grows into large numbers and spreads in human-made water systems, it can become a human health concern. Legionella can flourish in human-made water systems like hot tubs, cooling towers, showerheads and decorative fountains.

Please note: air-conditioning units do not use water to cool air, so they are not at risk of Legionella growth.

Signs and Symptoms

Legionnaires’ disease Pontiac fever
  • Fever
  • Cough
  • Shortness of breath
  • Muscle aches
  • Headache
  • Nausea / Vomiting
  • Confusion

Symptoms appear 2–14 days after exposure

  • Fever
  • Muscle aches

Symptoms appear 3 hours–3 days after exposure

Risk Factors

Most healthy people exposed to Legionella do not get sick. People who are at higher risk of severe disease include:

  • People 50 years or older
  • Current or former smokers
  • People with chronic lung disease
  • People with weak immune systems or who take drugs that weaken the immune system
  • People with cancer
  • People with underlying illnesses such as diabetes, kidney failure, or liver failure

What to do if you think you have Legionellosis (Legionnaires’ disease or Pontiac fever)?

If you think you have Legionnaires’ disease, please reach out to a healthcare provider (primary care physician, emergency department, etc.). If the healthcare provider suspects Legionnaires’ disease, laboratory tests will be conducted to confirm the presence of Legionella. Laboratory tests for Legionnaires’ disease include a urine antigen test and a lower respiratory culture. Antibiotics are used to treat Legionnaires’ disease.

If you think you have Pontiac fever, most people recover at home within 2–5 days without treatment.


There is no vaccine to prevent legionellosis. The presence of Legionella can be reduced by properly maintaining water systems where the bacteria grow (such as heating, cooling and plumbing systems).

Healthcare Provider Reporting

Healthcare providers must report all cases of legionellosis to DC Health within 48 hours. Report cases to DC Health by completing a Notifiable Disease and Condition Case Report Form or by calling the Division of Epidemiology at (844) 493-2652.

Please review the Online Notifiable Disease Case Report Form User Guide for information on how to complete and submit the online case report form.

Additional Resources

DC Health Contact Information

  • Contact Email: [email protected]
  • Contact Phone: (844) 493-2652
  • Contact Fax: (202) 442-8060