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Germs that infect humans

Legionella pneumophila

Legionella pneumophila

© Dennis Kunkel Microscopy, Inc.

Microorganism: the bacterium Legionella pneumophila

Disease: legionnaire’s disease

Occurrence of the disease

History: the name of the disease originates from a pneumonia epidemic that occurred in 1976 during a convention of the "American Legion." The bacteria responsible for these pneumonia cases were found to be located in the air conditioning system.

Current situation: in 1988, 104 cases of legionnaire’s disease were reported in Canada, including 26 from the province of Quebec.

Mechanism of action of the disease: when the bacterium reaches the lungs, it becomes a parasite of the lungs' immune cells and releases toxins causing destruction of the nearby tissues.

Symptoms of the disease: high fever, cough, headache, and severe pneumonia

Incubation period: from two to ten days

Contagious period: there is no documentation concerning person to person transmission

Hosts: The reservoirs for this disease are probably aqueous media such as hot water tanks, air conditioning systems, and humidifiers.

Transmission: many studies support the hypothesis that the bacteria might be spread through air. Water aspiration might also be a transmission mechanism.

Treatment: antibiotics such as erythromycin

Geographical distribution of the microorganism: North and South America, Australia, Africa, and Europe

Prevention: periodic cleaning of water tanks and air conditioning systems, use of cleaning products, maintaining hot water at a temperature above 50° C.

Vaccine: not available