Legionella

Legionella is a bacterium that occurs in two distinct clinical forms:

Legionnaires disease appears as a form of pneumonia ranging from a mild illness to a severe life threatening disease.

Pontiac fever is a mild condition with self-limiting symptoms similar to those of moderate influenza. Legionnaires’ disease acquired its name in 1976 when an outbreak of pneumonia occurred among persons attending a convention of the American legion in Philadelphia.

How does a person become infected?

Legionella exist naturally in water, moist soils, compost and potting mix. Infection results from inhalation of contaminated water sprays or mists. The bacteria live in water and colonize hot-water systems at temperatures of 20-50°C (optimal 35-46°C). They contaminate air-conditioning cooling towers, hot-water systems, humidifiers, whirlpool spas and other water-containing devices. There is no direct person-to-person transmission.

People of any age may get Legionnaires’ disease, but the illness most often affects middle-aged and older persons, particularly those who smoke cigarettes or have chronic lung disease. Also at increased risk are persons whose immune system is suppressed by diseases such as cancer, kidney failure requiring dialysis, diabetes, or AIDS. Those that take drugs that suppress the immune system are also at higher risk.

Pontiac fever most commonly occurs in persons who are otherwise healthy.

Signs and symptoms of the illness

Patients with Legionnaires’ disease usually have fever, chills, and a cough. Some patients also have muscle aches, headache, tiredness, loss of appetite, and occasionally, diarrhea. Chest x-rays often show pneumonia. The incubation period for legionella ranges from two to ten days, but is usually five to six days.

Patients with Pontiac fever experience fever and muscle aches and do not have pneumonia. The incubation period is between a few hours and three days. Patients generally recover in 2 to 5 days without treatment.

Treatment of legionellosis

Treatment includes supportive care and antibiotics.

Summary

Legionella occurs in two distinct clinical forms: Legionnaires disease and Pontiac fever.
Legionella exist naturally in water and moist soils. Infection results from inhalation of contaminated water sprays or mists.
Susceptibility to legionellosis increases with age, especially among smokers and people with pre-existing chronic lung disease or other immuno-compromising conditions.
Patients with Legionnaires’ disease usually have fever, chills, and a cough. Some patients also have muscle aches, headache, tiredness, loss of appetite, and occasionally, diarrhea.
Patients with Pontiac fever experience fever and muscle aches and do not have pneumonia. This condition is self-limiting.
Treatment includes supportive care and antibiotics.

More information

For more information about legionellosis, please contact your doctor or a health protection officer from the Health Protection Unit (telephone (07) 838 2569).

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