Legionella in Switzerland: what you should know

Legionella: how to protect yourself from infection

Legionella bacteria live in water pipes, cooling towers and air conditioning systems, and enter our lungs via the smallest water particles. Once they’re there, they can cause serious infections. The number of people getting ill from the bacteria in Switzerland is increasing year on year.

AuthorSWICA Content Team

3 minutes reading time08. September 2026

2026-09-08-gw-blog-feuchtgebiet-algen-legionellen-keime-getty

Legionella bacteria and their effects

Legionella are small, rod-shaped bacteria. They are most widespread in warm water. They occur naturally in almost all watery and humid environments, and they like water temperatures between 25 and 45 degrees Celsius. There are different types of Legionella. For humans, Legionella pneumophila is the most common cause of disease.

Legionellosis, which includes Legionnaires’ disease, is the more serious of the two diseases that can be caused by Legionella. It can have serious consequences and, in the worst case, may be fatal. The milder disease is Pontiac fever, which causes flu-like symptoms such as fever, cough, muscle aches and headaches. Pontiac fever clears up on its own after a few days and Legionella is often not pinpointed as the cause because the symptoms are similar to other, harmless viral diseases.

Legionella infection occurs via aerosols, i.e. water particles carried in the air. The aerosols enter the airways and affect lung function. However, there is no danger to your system if you swallow contaminated water, as stomach acid kills Legionella.

Risk groups and sources of infection

The risk of contracting Legionnaires’ disease is particularly high for smokers, people with pre-existing lung conditions or weakened immune systems, and older people from around 60 years of age. Experts have found that chronic diseases such as diabetes or cardiovascular problems also increase the risk of the disease. According to the FOPH, men are about two to three times more susceptible than women.

Legionella, like many other bacteria, multiply particularly rapidly in humid environments and warm water temperatures. That means that systems and equipment in which warm, stagnant water is present and finely atomised are potential sources of infection. Typical examples are hot tubs, showers, air conditioners, humidifiers and cooling towers. However, heating systems and water pipes in general can also be breeding grounds for Legionella, especially if hot water has been standing in them for a long time or if the pipes promote the attachment and growth of Legionella, for example due to mineral deposits.

2026-09-08-gw-blog-klimaanlage-hitze-legionellen-keime-getty

Reasons for rising cases

The number of Legionella infections is steadily increasing. This is partly due to more frequent reporting and better testing. But the FOPH also believes that hotter summer temperatures are increasingly creating ideal conditions for Legionella to spread. Demographic trends are also seen as one of the possible reasons, as older people have a higher risk of contracting legionellosis. In addition, changes in the construction industry affect the risk of infection if water hygiene standards are not being adhered to.

How to protect yourself from Legionella

Individuals with an increased risk of infection are advised to equip water sources at home with a Legionella filter. The following measures are recommended for effective protection against Legionella at home:

Perform periodic inspection and maintenance work on water sources
Regular descaling of water heating systems and fittings
Set your boiler to 60 degrees Celsius and do not allow cold water to get warmer than 25 degrees.
There is no mandatory general, periodic testing for privately rented flats. Strict requirements and testing obligations apply primarily to public institutions, hospitals, hotels, indoor swimming pools and commercial shower facilities as part of self-monitoring