Legionnaire's disease

Alternative names:

Legionella pneumonia

Definition:

An acute respiratory infection caused by the bacteria Legionella pneumophilia, which causes a serious pneumonia.

Causes, incidence, and risk factors:

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.