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Legionella are bacteria that can cause illness in humans. They cause symptoms ranging from mild flu to severe pneumonia. Legionella are found worldwide in the environment, for example in surface water and groundwater, but only in small quantities.
The bacteria multiply particularly well at temperatures between 25 and 45°C. At temperatures above 55°C, their growth is severely inhibited, and at temperatures above 60°C, they die. At temperatures below 20°C, they hardly multiply at all.
Legionella bacteria can enter the lungs via tiny water droplets (aerosols), such as those produced when showering, and cause Legionnaires' disease, a severe form of pneumonia.
Legionella bacteria are released into the air in fine water droplets and transmitted when inhaled. Possible sources of infection include showers, whirlpools, humidifiers, taps and cooling towers. There are many other sources. Important: Transmission from person to person is not possible.
Most infections are mild and similar to the flu. Symptoms include fever, headache, aching limbs, chest pain and coughing. The symptoms usually subside on their own after 2 to 5 days. In more severe cases, high fever (above 39°C), shortness of breath, coughing and chills occur.
People with a weak immune system are particularly at risk, including the elderly, smokers and people taking medication to suppress the immune system. Men are more likely to fall ill than women, and children rarely fall ill.
Pneumonia caused by Legionella bacteria must always be treated with antibiotics. Hospital treatment is often necessary. It is important to find and eliminate the source of infection quickly to prevent further cases.
Run taps and showers for at least one minute after prolonged periods of non-use, especially after holidays.
The Drinking Water Regulations stipulate that drinking water must be tested regularly for Legionella. Since November 2012, this testing requirement has also applied to water heating systems. This means that the water must be tested regularly for Legionella to ensure that it is safe. Further information on Legionella in drinking water can be found here.