Legionnaires' Disease

Legionnaires' disease is a serious type of pneumonia caused by Legionella bacteria. It takes its name from an outbreak among people attending an American Legion convention. The same bacteria can also cause Pontiac fever, a milder, flu-like illness that does not infect the lungs.

Where the bacteria live

Legionella occurs naturally in fresh water such as lakes and rivers, and in soil. People usually get sick only when it grows and spreads in human-made water systems — hot tubs, fountains, and the plumbing of large buildings such as hotels and nursing homes. You generally cannot be infected by drinking water containing the bacteria unless you accidentally breathe it into your lungs (aspirate it), and the disease does not spread from person to person. Outbreaks happen when many people are exposed to the same contaminated water source.

Who is at risk

Most healthy people exposed to the bacteria do not get sick. Infection is more likely if you:

• are over 50;
• smoke now or used to;
• have a chronic disease such as diabetes or kidney failure;
• have a chronic lung disease such as COPD or emphysema;
• have a weakened immune system from a disease such as HIV or cancer, or from immune-suppressing medicines;
• live in a long-term care facility;
• recently stayed in a hospital or had surgery under anesthesia.

Symptoms

Symptoms usually start 2 to 14 days after exposure and resemble those of other pneumonias, but Legionnaires' disease can also cause digestive symptoms and mental changes:

• cough;
• high fever;
• chills;
• headache;
• chest pain;
• shortness of breath;
• fatigue;
• nausea and vomiting;
• diarrhea;
• confusion.

It can lead to life-threatening respiratory failure, kidney failure and sepsis. About 1 in 10 people who get sick with it die of complications.

Diagnosis and treatment

A provider will usually order a chest x-ray to look for pneumonia. If it is present, urine or sputum tests can look for Legionella, and a blood test can show exposure to it. Most patients need hospital care and are treated with antibiotics. Most recover, especially if they were healthy before, and early treatment improves the chances.

Prevention

• Clean water-using devices regularly, including portable humidifiers, water heaters, air conditioners and nasal rinse devices.
• If faucets and showerheads have gone unused for a week or more, run the hot and cold water for at least two minutes before using them.
• Stay away from decorative fountains and hot tubs if you do not know how well they are maintained.
• Fill your car's wiper fluid tank with windshield washer fluid, not water.
• Ask how well the water systems in your buildings are maintained.

Sources

• MedlinePlus, National Library of Medicine: "Legionnaires' Disease," drawing on the Centers for Disease Control and Prevention. The source writes "decorative foundations" where fountains are meant; it is corrected here.