Legionnaires‘ Disease

Legionnaires‘ disease is a virulent form of pneumonia. Like other pneumonias, it is an inflammation of the lung 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. Either or both of these two illnesses may be 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. Patients acquire Legionnaires‘ Disease by inhaling water droplets containing the contaminating bacteria from a variety of sources. Possible sources of contaminated water include:

  • Hot tubs
  • Swimming pools
  • Physical therapy equipment
  • Large air-conditioning systems

Since large air-conditioning systems may be contaminated, Legionnaires‘ disease may spread through hospitals, nursing homes or cruise ships where the air supply is mostly self-contained.

Risk Factors for Legionnaires‘ Disease

Most people exposed to the bacteria causing Legionnaires‘ disease do not become ill. Patients are more susceptible to Legionnaires‘ if they:

  • Have weakened immune systems
  • Smoke heavily
  • Abuse alcohol
  • Are age 50 or older
  • Have undergone organ transplants
  • Have chronic lung disease
  • Are undergoing chemotherapy
  • Are taking steroid medications

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. These symptoms may include:

  • Fatigue
  • Headache
  • Loss of appetite
  • Muscle pain
  • Fever higher than 104 degrees Fahrenheit
  • Chills

After two or three days, the patient may develop other symptoms, including:

  • Coughing, sometimes producing bloody mucus
  • Shortness of breath
  • Chest or joint pain
  • Nausea, vomiting and diarrhea
  • Confusion or memory loss
  • Coordination difficulty

Diagnosis of Legionnaires‘ Disease

Legionnaires‘ disease is diagnosed by a thorough physical examination and a variety of diagnostic tests which may include

  • 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, or CBC, but a study of blood gases and sedimentation rate as well.

Treatment of Legionnaires‘ Disease

Legionnaires‘ Disease is treated by the administration of antibiotics. The doctor may prescribe a course of antibiotics for the patient even before the diagnosis is complete, since the earlier such treatment begins, the better the outcome is likely to be. Oxygen may also be administered if necessary, supplied either through a mask or through the use of a breathing machine. 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 it not treated promptly and efficiently. With Legionnaires‘ disease there is also a risk of respiratory failure, septic shock or kidney failure. It is important that Legionnaires‘ disease be diagnosed and treated as quickly as possible.

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,may persist from many months to up to a year.

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