Legionnaires' Disease
Legionnaires' disease is a virulent form of pneumonia, which is an inflammation of the lungs resulting from infection. Also known as "legionella," Legionnaires' disease is caused by a bacterium known as Legionella bacterium. This bacterium also causes Pontiac fever, a milder illness with flu-like symptoms. Both illnesses are also referred to as "legionellosis." Pontiac fever usually clears on its own; Legionnaires' disease, if not properly treated, can be fatal.
Causes of Legionnaires' Disease
Legionnaires' disease is not contagious. It is acquired by inhaling water droplets containing the bacteria. Possible sources of contaminated water include the following:
- Hot tubs
- Swimming pools
- Physical therapy equipment
- Large air-conditioning systems
When large air-conditioning systems are contaminated, Legionnaires' disease can spread. Hospitals, nursing homes and cruise ships, in which the air supply is mostly self-contained, are particularly susceptible.
Risk Factors for Legionnaires' Disease
Most people exposed to the bacteria causing Legionnaires' disease do not become ill. Susceptibility to Legionnaires' disease is greater in people who:
- Have weakened immune systems
- Smoke heavily
- Abuse alcohol
- Are aged 50 or older
- Have undergone organ transplants
- Have chronic lung disease
- Are undergoing chemotherapy
People who take steroid medications are also at increased risk for Legionnaires' disease.
Symptoms of Legionnaires' Disease
The first symptoms of Legionnaires' disease usually appear about 14 days after exposure and are similar to those of the flu. Symptoms include the following:
- Fatigue
- Headache
- Loss of appetite
- Muscle pain
- Chills
- Fever higher than 104 degrees Fahrenheit
After 2 or 3 days, other symptoms may develop, including those below:
- Coughing (sometimes producing bloody mucus)
- Shortness of breath
- Chest or joint pain
- Nausea, vomiting and diarrhea
- Coordination difficulty
Confusion and/or memory loss are also symptoms.
Diagnosis of Legionnaires' Disease
Legionnaires' disease is diagnosed by a thorough physical examination, and a variety of diagnostic tests that include the following:
- Chest X-ray
- Blood tests
- CT scan of the brain
- Liver-function tests
- Bronchoscopic culture of sputum
- Urine tests
The blood tests for Legionnaires' disease usually include not only a complete blood count (CBC), but a study of blood gases and sedimentation rate.
Treatment of Legionnaires' Disease
Legionnaires' disease is treated with antibiotics, which may be prescribed even before the diagnosis is complete, because the earlier treatment begins, the better the outcome is likely to be. Oxygen, supplied either through a mask or by a breathing machine, may also be administered. The patient may be given intravenous fluids, sometimes containing electrolyte replacements.
Complications of Legionnaires' Disease
Legionnaires' disease may cause infections elsewhere in the body, particularly in the heart, if not treated promptly and effectively. With Legionnaires' disease, there is also a risk of respiratory failure, septic shock or kidney failure.
Recovery from Legionnaires' Disease
If treated promptly, full recovery from Legionnaires' disease is likely, particularly if the patient is free of underlying conditions. Fatigue and mental confusion, however, can persist from many months to up to a year.