Legionnaire's disease: clear guide to symptoms, diagnosis, treatment, and prevention
Legionnaire's disease is a type of bacterial pneumonia caused by Legionella that grows in warm water systems. It can come on fast and hit hard, especially in older people, smokers, or anyone with a weak immune system. If you get a high fever, a persistent cough, or shortness of breath after staying in hotels, using hot tubs, or being near cooling towers, get checked.
What to watch for
Symptoms usually start 2–10 days after exposure. Early signs include fever, chills, muscle aches, headache, and a dry cough. Later you may notice chest pain, trouble breathing, confusion, nausea, vomiting, or diarrhea. The mix of lung and stomach symptoms can be a clue. Always tell your clinician about recent travel, hotel stays, or work around plumbing, air-conditioning, or spas.
How doctors test and treat it
Diagnosis uses a few tests: a rapid urine antigen test that finds the common Legionella strain, PCR or culture from respiratory samples, and a chest X-ray to see lung changes. The urine test is fast but mainly detects Legionella pneumophila serogroup 1, so culture or PCR helps catch other types and is vital for outbreak tracing.
Treatment is with antibiotics that get into lung tissue well. Doctors commonly use a fluoroquinolone (like levofloxacin) or a macrolide (like azithromycin). Many patients need hospital care for oxygen, IV fluids, and close monitoring. People usually start to feel better in a few days once antibiotics begin, but severe cases can take weeks to fully recover.
Typical courses run 7–14 days for milder illness and longer for serious infections. Follow-up chest X-rays or clinic checks ensure the lungs are healing. If symptoms return after treatment, contact your provider — sometimes a change or extension of antibiotics is needed.
Public health reporting matters. Labs often must report confirmed cases so health departments can check for linked cases and inspect buildings. During outbreaks, environmental cultures help match patient strains to water sources and guide disinfection.
Prevention focuses on keeping water systems safe. Legionella thrives in warm, stagnant water and spreads in aerosolized mist. Building owners should flush unused pipes, maintain hot water heaters at recommended temperatures, clean and disinfect cooling towers and hot tubs, and control biofilm with approved disinfectants. Regular monitoring and quick fixes cut risk a lot.
You can reduce personal risk by avoiding poorly maintained hot tubs, running taps for a minute after a long building shutdown, and not standing near unknown decorative fountains or cooling tower mist. If you travel, pick places with good maintenance reviews when possible.
Quick checklist: seek care for high fever or breathing trouble; tell providers about recent travel or building exposure; ask for urine antigen plus respiratory testing if Legionella is suspected; building managers should flush systems, check temperatures, and schedule routine disinfection.
