7 August 2007
Outbreak of Legionnaires' disease
It was reported that approximately 170 people were hospitalized in the Urals region of Russia following a pneumonia outbreak. The outbreak was believed to be related to the growth of legionella bacteria in hot drinking water supplies. Four patients have died. The vast majority of the cases have been diagnosed with Legionnaires' disease, which has been confirmed by laboratory results.
Legionellosis is a collection of infections that emerged in the second half of the 20th century. The infections are caused by Legionella pneumophila and related Legionella bacteria. The severity of legionellosis varies from mild febrile illness (Pontiac fever) to a potentially fatal form of pneumonia (Legionnaires’ disease). Legionnaires’ disease can affect anyone, but principally affects people who are susceptible due to age, illness, immunosuppression or other risk factors, such as smoking.
Water is the main natural reservoir for Legionella bacteria. They are found worldwide in many different natural and artificial aquatic environments, such as:
- cooling towers
- water systems in hotels, homes, ships and factories
- respiratory therapy equipment
- misting devices
- spa pools.
About 20% of the cases of legionellosis detected in Europe are travel related; these cases present a particular set of problems because of difficulties in identifying the source of infection. WHO has recently finalized a reference document for public health professionals — Legionella and the prevention of legionellosis — to review the current state of knowledge about the impact of Legionella on health.