Legionnaires' Disease — Causes, Symptoms, and Prevention

Legionnaires’ disease is a severe pneumonia caused by Legionella bacteria. People get sick by inhaling tiny water droplets containing the bacteria — not from drinking water and not from person-to-person spread (extremely rare). Outbreaks often trace back to poorly maintained water systems.

How infection happens

• Aerosolized water from cooling towers, decorative fountains, showers, hot tubs/spas, humidifiers, or complex plumbing.
• Bacteria thrive in stagnant, warm water (20–45°C / 68–113°F), biofilms, and scale.

Symptoms & timing

• Starts 2–10 days after exposure (occasionally up to 14 days).
• High fever, chills, cough (dry or productive), shortness of breath, chest pain.
• Often includes headache, muscle aches, fatigue, and sometimes diarrhea or confusion.

Who is most at risk

• Age 50+, smokers, people with chronic lung disease, diabetes, kidney disease, cancer, or weakened immunity.
• Recent hotel/cruise stays, hospitalization, or buildings with complex water systems.

Prevention — practical steps

• Prefer well-maintained accommodations; look for good hygiene standards.
• Avoid or limit time near steamy hot tubs or decorative fountains in unclear maintenance settings.
• In rooms unused for a while, run the shower hot for a few minutes with the door closed before use.
• Facility owners should follow water safety plans (regular flushing, temperature control, biocide, sediment control).

When to seek medical care

• Pneumonia symptoms (fever, cough, shortness of breath), especially after hotel/spa/cruise or healthcare exposure.
• Tell clinicians about recent travel or exposure to water systems; this helps trigger Legionella testing.
• Early diagnosis and appropriate antibiotics improve outcomes.

This guide is for general information and isn’t a substitute for professional medical advice. Seek emergency care for severe breathing difficulty, confusion, or chest pain.

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