What is it?

Legionellosis refers to two different forms of disease: Legionnaires’ Disease and Pontiac Fever. Both are caused by exposure to Legionella bacteria.

• Legionnaires’ Disease is a severe form of pneumonia
• Pontiac Fever is a mild respiratory illness and does not include pneumonia

Symptoms

Who can get it? 

Anyone can be exposed to Legionella bacteria or develop Legionellosis, but certain people are at an increased risk of severe disease:

• People who are 50 years or older
• People who smoke (current or former)
• People with chronic lung disease
• People with a weakened immune system or who take medication that weakens their immune system
• People with cancer
• People with underlying illnesses (diabetes, kidney failure, or liver failure)
   

Treatment

• Legionnaires’ Disease is treated with antibiotics and often requires hospitalization.
• Pontiac Fever usually resolves without requiring treatment, in less than a week.

Is a person with Legionnaires' Disease contagious? 

In general, people do not spread Legionellosis to other people. However, this may be possible in rare circumstances. 

What if I think I have it? 

Reach out to a healthcare provider or visit a healthcare facility (primary care physician, urgent care, emergency department) if you think you have Legionellosis. The healthcare provider will conduct laboratory tests if they suspect Legionellosis.

How can you prevent it?  

There are no vaccines to prevent Legionellosis. Instead, the key is to reduce the risk of Legionella growth and spread. You can also avoid or limit your exposure to aerosolized water. For example, by taking a bath instead of a shower.

• Preventing Legionellosis at Home-2025.pdf

Legionella Bacteria 

• You can be exposed to Legionella if you breathe in small, misty, aerosolized droplets of water that contain the bacteria (Legionella enters your lungs).
• • Ingesting or drinking water that contains Legionella, does not cause Legionellosis (Legionella enters your stomach).
• Less commonly, you can be exposed during the aspiration of water containing Legionella. This happens when water accidentally goes into the lungs while drinking.

Where can you be exposed to Legionella?

Legionella can grow and spread in human-made water systems. Legionella can cause Legionellosis through aerosolized or misty water sources.

Where does Legionella come from?

Legionella bacteria live in natural water sources like lakes and rivers. Typically, exposure to Legionella from natural water sources does not cause Legionellosis (due to the small amount of Legionella). Legionella becomes a concern when it grows and spreads in human-made water systems.

Legionellosis in DC   

Information for Building Owners and Managers 

Building owners and managers should utilize a facility-specific Water Management Program/Plan to reduce the risk of Legionella growth and spread.

• Legionellosis Prevention Checklist for Building Owners/Managers-DC Health-2024.pdf
• Legionellosis Prevention Cooling Towers & Hot Tubs-DC Health-2024.pdf
• Legionellosis Prevention: Decorative Water Fountains-DC Health-2025.pdf
• Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings-CDC-2024.pdf

Information for Healthcare Providers 

Additional Resources

• Fact Sheet-Legionellosis-DC Health-2025.pdf
• Fact Sheet-Legionellosis-Spanish-DC Health-2025.pdf
• Recreational Water Illnesses-DC Health-2025.pdf
• Preventing Recreational Water Illnesses at Splash Pads/Spray Parks-DC Health-2025.pdf
• How Legionella Affects Building Water Systems and People-CDC-2021.pdf
• CDC Website: Legionella (Legionnaires’ Disease and Pontiac Fever)
• Public Health Water Advisory-DC Health-2025.pdf (PDF)

DC Health Contact Information

• Contact Email: [email protected]
• Contact Phone: (202) 442-5955
• Contact Fax: (202) 442-8060