Legionella

Legionella ssp.

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Changed on: 08.04.2019
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Legionella are rod-shaped, non-sporolous, gram-negative bacteria and members of the family Legionellaceae. The sole genus Legionella includes over 40 named species with more than 60 different serogroups, a small number of which are actually pathogenic for humans. The species that is most important from an epidemiologic perspective is Legionella pneumophila, which has at least 15 serogroups, with serogroup 1 being discovered in about 90 % of human legionellosis in Austria.

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Legionella are rod-shaped, non-sporolous, gram-negative bacteria and members of the family Legionellaceae. The sole genus Legionella includes over 40 named species with more than 60 different serogroups, a small number of which are actually pathogenic for humans. The species that is most important from an epidemiologic perspective is Legionella pneumophila, which has at least 15 serogroups, with serogroup 1 being discovered in about 90 % of human legionellosis in Austria.

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Transmission

Breathing in aerosols (very fine water droplets) contaminated with legionella or particulates may cause serious pneumonia, the so-called Legionnaire’s disease. Drinking water contaminated with legionella presents no health risk. Individuals with weakened immune systems, chronic lung infections and smokers have a higher infection risk. Transmission from human to human is not possible.

Infection through Plant Soil

Legionnaire’s disease is primarily caused by legionella pneumophilia in Europe. However, there are other types of legionella, which are also spread widely and might also lead to an infection. There are an increasing number of cases of Legionnaire’s disease registered worldwide, in particular in Australia, but also in Europe, caused by the species legionella longbeachae. In these cases, the infection source seems to be commercial plant soil, as was the case in a fatality in Austria in 2008. The risk of catching Legionnaire’s disease through breathing in fine particulates of plant soil or compost contaminated with legionella is very low. AGES documented two such cases in 2009.

In Australia, where infections with legionella longbeachae are more common, the soil is labelled with a warning and it is recommended to moisten the soil before use to prevent soil particulates getting airborne, wearing gardening gloves and washing hands thoroughly after working with the soil. Additionally, it is occasionally recommended to wear protection masks when handling the soil.

Prevention

Many countries have set up national surveillance systems for legionella infections, following the discovery of this infectious disease in 1976. Authorities must be notified about any suspicion, infection or fatality in relation to Legionnaire’s disease. The epidemiologic surveillance based on the reports provided by doctors and laboratories, as well as the surveillance programme of the National Reference Centre for Legionella Infections, enables the rapid identification of clusters (i.e. accumulation of cases). The relevant regional administrative authorities, supported by AGES infection epidemiologists, can conduct the appropriate outbreak clarification with immediate identification and elimination of the source of the infection.

More detailed information on prevention can be found in the download area: Guidelines for Legionella.


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