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Swimming pool in Bonn: Hardtbergbad closes due to Legionella in drinking water

Swimming pool in Bonn : Hardtbergbad closes due to Legionella in drinking water

In the drinking water system of the Hardtbergbad the limits for Legionella have been exceeded. Because the pipe system now has to be disinfected, the swimming pool will close for two days according to the city council.

A high concentration of Legionella was found in drinking water samples of the Hardtberg indoor swimming pool. According to the administration, the limit values were exceeded. In order to avert the risk of infection, the entire pipe system is to be disinfected with chlorine dioxide. Therefore, the outdoor swimming pool will be closed on Monday and Tuesday next week. The indoor swimming pool is scheduled to start operation on 30 September.

Although according to the administration no harmful Legionellen concentration was determined in the outdoor swimming pool, which is still open at present, also that must beflushed. Afterwards samples will be taken again. Further questions about the Legionella contamination, which the GA addressed to the city in writing on Wednesday afternoon upon request, were not answered by the press office. Questions as to how far the concentration of harmful bacteria exceeds the limit value and what kind of bacteria remained unanswered until the evening.

"Legionellosis is not a lapidary disease", Professor Martin Exner, Director of the Bonn Institute for Hygiene and Public Health, told the GA. Legionella is his area of expertise. He considers the decision of the administration to close the outdoor pool for large-scale disinfection to be the right one. In any case, it is important to "act transparently".

Exner: Statistics only show the tip of the iceberg

Legionella are permanently present in the natural environment. "They become a danger if the concentration is too high," explained Exner. "Legionella is not harmful if you drink the water. However, if the finest water sprays with a high concentration of Legionella enter the air and are inhaled, they cause infections. They do not affect the stomach or intestines, but the lungs. The infection can lead to death.“ According to Exner, people over the age of 50 and smokers are more susceptible.

The problem with the current examination procedure is that water samples are only available after ten days. This means that the system was theoretically contaminated ten days ago. Exner also does not speak of a limit value, but of a "technical measure value", from when action must be taken. This is based on a finding of 100 legionella per 100 millilitres of water. Of course, a distinction must be made between the different types. The pathogens act aggressively in different ways.

Basically, Legionella multiply extremely quickly at water temperatures between 25 and 55 degrees. Therefore, it is important to constantly maintain swimming pool facilities "so that uncontrolled proliferation cannot occur". Last year, the Robert Koch Institute reported around 1500 cases of legionellosis nationwide. Exner: "These are the most serious diseases, and the statistics only show the tip of the iceberg. We assume that the figure is 15,000 to 30,000 patients in Germany."


Legionella are rod-shaped bacteria. They were first discovered in July 1976 at the Bellevue-Stratford Hotel in Philadelphia (USA). There 180 of 4400 delegates fell ill at a veterans' congress of the American Legion (Pennsylvania American Legion). There were 29 fatalities. Despite immediate research activities, it took until January 1977 to isolate the bacterium from the lung tissue of a deceased veteran.

According to Wikipedia, the transmission of Legionella is in principle possible by contact with tap water if the Legionella reaches the deep lung sections. Not every contact with water containing legionella leads to a health hazard. Only inhalation of water containing bacteria in the form of bioaerosol - aspiration or inhalation, for example in showers, air-conditioning systems, lawn sprinklers and whirlpools - can lead to infection.

Drinking water containing legionella is not a health hazard for people with an intact immune system. An infection is particularly associated with the following technical systems: hot water supplies (in residential buildings, hospitals, homes, hotels), air conditioning systems and humidifiers, swimming pools, especially whirlpools, other systems that atomize water into droplets (fog generators, fog fountains).

(Original text: Jutta Specht, Translation: Mareike Graepel)