On 3 November 2026, reports of Legionella in tap water are once again attracting public attention. Official guidance and recent studies paint a clear picture for Germany: Legionella in water is a real but localised health risk; the risk of illness depends on the concentration of the bacteria, the type of system and individual risk factors. The Robert Koch Institute (RKI) identifies inhalation of contaminated aerosols as the main route of transmission and gives the incubation period for Legionnaires’ disease as a severe form of pneumonia as Incubation period around two to ten days. Older people and those with chronic lung conditions or weakened immune systems are particularly at risk. ([rki.de](https://www.rki.de/DE/Themen/Infektionskrankheiten/Infektionskrankheiten-A-Z/L/Legionellose/OEGD/Leitfaden.html?utm_source=openai))
Studies in Germany show that domestic drinking water systems are more often identified as a source of infection than systems in publicly accessible facilities. The LeTriWa study (Legionella in drinking watersystems) and subsequent analyses showed that certain subtypes, particularly MAb 3/1-positive strains of Legionella pneumophila, are associated with an increased risk of illness. The RKI therefore recommends targeted sampling and risk assessments, and specific remedial measures when technical action thresholds are exceeded. ([rki.de](https://www.rki.de/DE/Aktuelles/Publikationen/Epidemiologisches-Bulletin/2024/33_24.pdf?__blob=publicationFile&v=2&utm_source=openai))
In practical terms, authorities and specialist organisations recommend the following evidence-based steps: ensure hot-water temperaturetemperatures that inhibit bacterial growth (regularly above 55 °C in central systems), regularly flush infrequently used pipes, maintain boilers and circulation systems properly, and take targeted samples for laboratory testing if Legionella is suspected. In some cases, thermal flushing, disinfection or structural measures are necessary; local health authorities decide on action based on laboratory results. Informing consumers and promptly reporting suspected cases to GPs and health authorities are part of routine practice. ([rki.de](https://www.rki.de/DE/Themen/Infektionskrankheiten/Infektionskrankheiten-A-Z/L/Legionellose/legionellose-node.html?utm_source=openai))
It is important to distinguish between the presence of Legionella in water and an acute epidemic: the risk is quantitative and depends on the context. Drinking the water itself poses little danger, as stomach acid usually inactivates the bacteria. However, showering in contaminated systems can cause infection through aerosols. The national assessment is based on current RKI guidance and surveillance data, which health authorities use as a basis for preventive measures and outbreak investigations. ([rki.de](https://www.rki.de/DE/Themen/Infektionskrankheiten/Infektionskrankheiten-A-Z/L/Legionellose/OEGD/Leitfaden.html?utm_source=openai))
Editor: Clara Simonichek (Article created with AI assistance).