Legionellosis

Legionella

Legionellosis is caused by a type of bacteria called Legionella.

These bacteria tend to live in wet environments. Examples include natural bodies of water, moist soil and man-made water systems. 

They thrive in warm water such as hot tubs, cooling towers and large plumbing systems. They also thrive in parts of air conditioning systems in large buildings.

Cases have increased statewide and globally in recent years. North Carolina reported 310 cases in 2025 compared to 201 cases in 2024.

People at higher risk

Most healthy people exposed to Legionella don't get sick. People most at risk include:

• People 50 years and older.
• People who smoke or previously smoked.
• People with a chronic disease or a compromised immune system.

How it spreads

People get Legionellosis by inhaling mist or vapor contaminated with Legionella. It is not spread through person-to-person contact. 

Common sources of exposure include: 

• Hot tubs
• Decorative fountains
• Cooling towers
• Hot water tanks
• Large plumbing systems
• Misting devices and humidifiers (if not properly cleaned and maintained) 
• Showerheads and sink faucets that haven't been used in 3+ days
• Garden hoses where unused water may have collected and sat

Home and car air-conditioning units do not use water to cool the air, so they aren't a risk for Legionella growth. This includes window units, like the kind seen at some hotels. 

Legionella can also grow in the windshield wiper fluid take if water is added instead of windshield wiper fluid. When the windshield is sprayed with mist to clean it, the bacteria can be inhaled.

Signs and symptoms 

Legionnaires' disease symptoms usually develop two to 14 days after exposure. Symptoms may include: 

• High fever
• Chills
• Cough
• Shortness of breath
• Muscle aches
• Headaches
• Other symptoms such as confusion, diarrhea or nausea

Pontiac Fever symptoms usually develop a few hours to three days after exposure. It lasts less than one week. Symptoms may include: 

• Fever
• Headache
• Muscle aches

No pneumonia: Unlike Legionnaires' disease, Pontiac fever does not involve pneumonia.

Legionnaires' disease can be serious and even fatal. Pontiac fever is generally milder than Legionnaires' disease and complications are not expected.

How to Prevent Legionnaires' Disease

Prevention practices include:

• Flush faucets and showerheads that have not been used for more than three days.
• Maintain and disinfect hot tubs correctly.
• Only use distilled water to rinse your sinuses.
• Use recommended water for in-home medical equipment. Devices may include CPAP and BIPAP machines, humidifiers, vaporizers, etc. Clean equipment regularly. 
• Follow instructions for cleaning and replacing water filters.
• Drain garden hoses to avoid stagnant water.
• Don't use tap water in place of windshield wiper fluid.  
• Avoid fountains and misters if you are at higher risk.

Get more prevention tips for Legionnaires' Disease.

Treatment and recovery

Treatment with antibiotics is effective for Legionnaires' disease, and healthy people usually recover. Pontiac fever usually resolves on its own without treatment or complications.