ENLmedical.com: Conditions And Concerns: Medical Encyclopedia: Legionnaire's disease

Legionnaire's disease

Causes and Risks:
The bacteria has been found in water delivery systems and can survive in the warm, moist, air conditioning systems of large buildings including hospitals. The infection is transmitted through the respiratory route. Person to person spread has not been proven.

From the onset of symptoms, a worsening of the condition is typical during the first 4 to 6 days, with improvement starting in another 4 to 5 days. 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 , cancer , diabetes or chronic obstructive pulmonary disease ; people with suppressed immune systems from chemotherapy , steroid medications or diseases such as cancer and leukemia ; alcoholism ; being middle-aged or elderly, and in chronically ventilated patients.

Prevention:
Active surveillance of infections that were acquired within a hospital can lead to the treatment of contaminated water delivery systems. Detection and treatment of sources outside hospitals usually occurs during or after an epidemic has happened.

Symptoms:

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
rales
diarrhea
ataxia ( lack of coordination )

Signs and Tests:
Listening to the chest with a stethoscope ( auscultation ) reveals fine crackles.

Sputum DFA (direct fluorescent antibody) staining shows Legionella.
Chest X-ray shows pneumonia .
Arterial blood gas analysis may show low concentrations of oxygen.
CBC shows an increased white blood cell count .
Erythrocyte sedimentation rate is increased.
Liver function tests may show moderate elevation.
The causative organism can be cultured from the airway, also.

Treatment:
The goal of treatment is to eliminate the infection with antibiotics. Treatment is started as soon as Legionnaire's disease is suspected, without waiting for confirmation by culture results. Erythromycin is the drug of choice. Rifampin may be added to improve results.

Supportive treatment includes hospitalization for fluid and electrolyte replacement and oxygen administration by mask or by mechanical ventilation, if the respiratory system becomes severely compromised by the infection.

Prognosis:
The overall death rate for those with pneumonia is about 15%, and the death rate increases in those with underlying diseases.

Complications:

respiratory failure requiring mechanical ventilation (use of a respirator)

Call Your Healthcare Provider:
Call your health care provider if breathing difficulties develop.

Legionnaires disease was first described in 1976 after and outbreak of fatal pneumonia at a Legionnaires convention. The newly described organism which caused the disease was named Legionella pneumophila, shown in this picture. (Courtesy of the Centers for Disease Control.)