Legionnaires' Disease Fact Sheet (PDF)

Specific prevention resources for the general public, healthcare providers, and businesses are located at the bottom of this page.

What is Legionnaires’ disease?

Legionnaires’ disease is a respiratory infection (pneumonia) caused by legionella, a bacterium that occurs naturally in freshwater like lakes and streams. Legionella can grow in water sources like water pipes, water heaters, and water storage tanks. 

Most healthy people recover, but Legionnaires’ disease can be very serious if untreated. A milder form of this infection, Pontiac fever, is an influenza-like illness without pneumonia that resolves on its own.   

Who can get Legionnaires’ disease?

Anyone can get Legionnaire’s disease. Current or former smokers, adults age 50 years and over, those with chronic lung conditions, and people with weakened immune systems have a higher risk of getting Legionnaires' disease.

How is Legionnaires’ disease spread?

People can get Legionnaires’ disease when they breathe in droplets of water in the air that contain the legionella bacteria. Legionnaires’ disease is not spread from person to person. Common sources of exposure include:

• Cooling towers (large building air conditioning systems)
• Whirlpool spas and hot tubs
• Hot water tanks
• Decorative fountains
• Showers

Home and car air conditioners do not use water to cool the air, so they do not pose a risk for legionella growth. 

What are the symptoms of Legionnaires’ disease?

Common symptoms include:

• Fever (typically between 102-105 degrees)
• Chills
• Cough
• Shortness of breath
• Muscle aches
• Headaches
• Confusion
• Nausea
• Diarrhea
• Chest pain

Symptoms typically occur 2-14 days after exposure. Antibiotics are used to treat Legionnaires’ disease. Prompt diagnosis of the disease is important. Talk to your doctor if you believe you were exposed to legionella and develop symptoms.

How can Legionnaires’ disease be prevented?

• Quit smoking – this is the most important personal step to lower risk.
• In large buildings (especially in healthcare), water system maintenance is crucial to prevent legionella growth.
• Maintain and disinfect hot tubs, pools, and jetted tubs properly by ensuring proper chlorine and pH levels. 
• Use sterile, distilled, or boiled water (water that has been boiled, cooled, and placed in a clean container) for CPAP machines, nebulizers, and point-of-use humidifiers. 
  • Drain, clean, and sanitize these items, along with whole house humidifiers, regularly according to the manufacturer’s directions. 
• Drink and make ice with distilled or boiled water rather than tap water if you have a poor immune system or difficulty swallowing. 
• Flush hot water heaters on an annual basis or per manufacturer’s recommendations, and flush hot water lines (letting them run for 2-3 minutes) on a regular basis to prevent water from sitting inactive in the lines.

Additional Info