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Legionnaires' disease

Also called: Legionnaires' disease, Legionella pneumonia

A serious pneumonia caused by Legionella bacteria breathed in from contaminated water mist, like hot tubs, cooling towers, or showers. It needs antibiotics.

Spread byWater mist, not person to person
Higher riskOver 50, smokers, weak immune systems
TreatmentAntibiotics

Overview

Symptoms start 2 to 14 days after exposure with high fever, cough, muscle aches, and sometimes diarrhea or confusion.

Outbreaks are often linked to hotels, hospitals, or large buildings.

Symptoms

Common signs:

  • High fever and cough

Less common

  • Muscle aches
  • Shortness of breath
  • Diarrhea
  • Confusion

Look up a symptom: Cough · Fever · Getting winded easily with activity or stairs

When to get medical care

Call 911Trouble breathing or confusion.
Get care todayHigh fever with cough, especially after travel.
See a doctor soonCough lasting more than 3 weeks.

Causes

Legionella bacteria in water systems.

Does it spread or run in families?

  • It usually doesn't spread from person to person.
  • People get it from: breathing in water mist.

Who is more likely to get it

  • Over 50
  • Smoking
  • Chronic lung disease

Diagnosis

A clinician asks about your symptoms and may order tests.

The exam

A physical exam.

Tests

Tests, if needed:

  • Urine antigen test:
  • Chest X-ray:

Treatment

Treatment depends on the cause and how severe it is.

Self-care

  • Rest and drink fluids
  • Take all antibiotics
  • Tell your doctor about recent travel or hotel stays

Medicines

Medicines that may help:

MedicineHelps withGood to know
Antibiotics
Infection

OwieClear doesn't give doses: follow the label or your healthcare professional. Medicine names here are examples, not a full list.

Prevention

To lower your risk or catch problems early:

  • Keep hot tubs cleaned and disinfected

Which doctor treats this

  • Start with your primary care provider (family doctor or internist).
  • They may send you to an infectious disease specialist, for hard-to-treat infections.

Children, pregnancy, and older adults

  • Older adults: Higher risk of severe illness.

Pregnancy and breastfeeding

  • If you're pregnant or planning to be, tell your prenatal provider about this condition.
  • Some infections can pass to the baby during pregnancy or birth. Tell your provider if you've been exposed.
  • Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
  • Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
  • Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.

Outlook

Most recover with antibiotics, though tiredness can last weeks.

Getting ready for your visit

Bring a list of your symptoms and medicines.

What to bring

  • A list of your medicines and supplements
  • Notes on when symptoms started and what makes them better or worse

Questions to ask

  • What's causing this?
  • What treatment do you recommend?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Legionnaires' disease

Sources

Last updated 2026-11-12.