What Is Legionnaires Disease and Can It Come From Water Damage?
Last updated October 31, 2026
The short answer
Understanding Legionnaires Disease
Legionnaires disease is a serious lung infection you can get by breathing in tiny droplets of water that contain Legionella bacteria. It is not spread from person to person, and most healthy people who are exposed do not become ill. However, older adults, smokers, and people with weakened immune systems face a higher risk of severe illness.
The bacteria grow well in warm water between 77 and 108 degrees Fahrenheit, especially in stagnant conditions. You might encounter them in cooling towers, hot tubs, decorative fountains, and large plumbing systems. Symptoms include fever, cough, shortness of breath, and muscle aches, and they usually appear two to ten days after exposure.
How Water Damage Creates Risk
Water damage from leaks, floods, or high humidity can leave standing water in your home, which is exactly where Legionella can multiply. Carpets, drywall, and insulation that stay damp for days create a breeding ground. Even a small leak behind a wall can produce the warm, still conditions the bacteria prefer.
The risk rises when water sits in places like air conditioning drip pans, humidifiers, or hot water heaters. If your home has had water damage, you should dry affected areas thoroughly within 24 to 48 hours to limit bacterial growth. For large or hidden water damage, the pros can help with inspection and drying to reduce health risks.
If you live in a humid climate, the humid summers can make drying harder, so act quickly after any leak.
Signs of Water Damage to Address
You should look for water stains on ceilings or walls, peeling paint, musty odors, and warped flooring. These can signal hidden moisture that might support bacterial growth. Pay attention to areas around pipes, air conditioning units, and window seals where condensation can collect.
Also check your attic and crawlspace for damp insulation or standing water after heavy rain. A musty smell often means mold is growing, which is a separate but related concern. If you notice any of these signs, act quickly to find the source and dry the area.
For a thorough check, consider a water damage inspection to identify all affected spots.
- Water stains or discoloration on walls or ceilings
- Peeling or bubbling paint near water sources
- Musty or earthy smells in rooms or closets
- Warped or buckling hardwood floors
- Damp insulation in attic or crawlspace
- Visible mold growth on surfaces
Preventing Legionella Growth
Prevention starts with controlling moisture. Fix leaks promptly, dry wet areas completely, and keep indoor humidity below 60 percent. Clean and disinfect cooling systems, humidifiers, and hot tubs according to manufacturer instructions. If you have a hot water tank, keep the temperature above 140 degrees Fahrenheit to inhibit bacterial growth, but be careful to avoid scalding.
For areas that are hard to dry, like behind drywall or under carpet, you may need to remove and replace materials. The pros can handle drying, cleaning, and restoration to ensure your home is safe. If you suspect a large contamination, see a doctor if you feel unwell, and consult a mold professional if you see mold growth.
- Fix leaky pipes and roofs without delay
- Dry wet carpets and padding within 48 hours
- Keep indoor humidity below 60 percent
- Clean air conditioning drip pans regularly
- Maintain hot water temperature above 140 degrees Fahrenheit
- Use exhaust fans in bathrooms and kitchens
When to Seek Professional Help
If water damage is extensive, hidden, or has been present for days, professional help is wise. The pros have equipment to detect moisture behind walls and to dry structures thoroughly. They can also remove contaminated materials like drywall and carpet that you cannot effectively clean yourself.
You should also involve professionals if you have health concerns or if the water may contain sewage or chemicals. In such cases, your safety comes first, so evacuate and avoid contact. For routine water damage, a local water damage pro can help restore your home and reduce health risks.
Policies vary, and your insurer decides what is covered. Check your policy to understand your options.
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Call Now (614) 412-4391Frequently asked questions
Can legionnaires disease spread from person to person?
No, Legionnaires disease is not contagious. You get it by breathing in water droplets that contain Legionella bacteria. It does not spread through coughing or touching an infected person. If you have symptoms, see a doctor for evaluation.
How long after water damage do symptoms appear?
Symptoms usually appear two to ten days after exposure to Legionella bacteria. The incubation period can be up to two weeks in some cases. If you develop fever, cough, or difficulty breathing after water damage, seek medical care promptly.
Is mold from water damage the same as legionella?
No, mold and Legionella are different. Mold is a fungus that grows on damp surfaces, while Legionella is a bacterium that lives in water. Both can cause health issues, but they require different treatments. If you have mold, a mold professional can help with removal.