Viruses, as well as bacteria, are among the pathogens. However, unlike bacteria, viruses do not count as living organisms. They do not engage in cell division to reproduce, but require a host. Viruses therefore attack other cells, the so-called host cells, into which they introduce their own genetic information. The genetic information of the virus “reprograms” the host cell’s genome so that it produces many more viruses. Viruses such as influenza viruses are among the pathogens that can be transmitted fecal-orally through drinking water. These include viruses such as poliomyelitis virus (polio), Norwalk virus and Rota virus, which cause gastrointestinal diseases. Viruses can survive in drinking water for several weeks, depending on the water temperature. With disinfection of the water, these can be killed and rendered harmless.