Health Encyclopedia

Legionnaire's disease

Definition

Legionnaire's disease is an acute respiratory infection caused by the bacteria Legionella pneumophila.

Alternative Names

Legionella pneumonia; Pontiac fever

Causes, incidence, and risk factors

The bacteria that cause Legionnaire's disease have been found in water delivery systems and can survive in the warm, moist, air conditioning systems of large buildings, including hospitals.

Spread of the bacteria between humans has not been proven.

Most infection occurs in middle-aged or older people, although it has been reported in children. Typically, the disease is less severe in children.

Risk factors include:

Cigarette smoking
Underlying diseases such as renal failure, diabetes, or chronic obstructive pulmonary disease
Medicines that suppress the immune system, including chemotherapy and steroid medications
Diseases that affect the immune system, including cancer
Alcoholism
Older age
Long-term use of a breathing machine (ventilator)

Symptoms

Symptoms tend to get worse during the first 4 to 6 days. They typically improve in another 4 to 5 days.

Symptoms may include:

Muscle aches and stiffness
Joint pain
Loss of energy
General discomfort, uneasiness, or ill feeling (malaise)
Headache
Fever
Shaking chills
Nonproductive cough
Coughing of blood
Shortness of breath
Chest pain
Diarrhea
Ataxia (lack of coordination)

Signs and tests

The health care provider will perform a physical exam. The doctor may hear abnormal sounds called crackles when listening to the chest with a stethoscope.

Tests that may be done include:

Urine tests to check for bacteria
Chest x-ray
Arterial blood gas
CBC, including white blood cell count
Erythrocyte sedimentation rate
Liver function tests
Sputum direct fluorescent antibody test

Treatment

Antibiotics are used to fight the infection. Treatment is started as soon as Legionnaire's disease is suspected, without waiting for confirmation by lab test.

Antibiotics commonly used to treat this condition include:

Quinolones (ciprofloxacin, levofloxacin, moxifloxacin, or gatifloxacin)
Macrolides (azithromycin, clarithromycin, or erythromycin)

Other treatments may include:

Fluid and electrolyte replacement
Oxygen (given through a mask or breathing machine)

Expectations (prognosis)

Legionairre's disease can lead to death. The death rate increases in those with underlying diseases. The death rate for patients who develop Legionnaire's disease while in the hospital is close to 50%, especially when antibiotics are started late.

Complications

Lung failure
Death

Calling your health care provider

Make an appointment with your doctor if you have any type of breathing problem.

Prevention

Treating contaminated water delivery systems can prevent the spread of disease.

Review Date:6/20/2007
Reviewed By:Arnold L. Lentnek, MD, Division of Infectious Disease, Kennestone Hospital, Marietta, GA. Review provided by VeriMed Healthcare Network.

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