Legionella outbreak in Basel-Stadt: 26 cases, one death confirmed

Basel-Stadt has announced that it is currently tackling a Legionella outbreak. One person has died, and 25 people were hospitalised. Residents are urged to watch out for symptoms of pneumonia.

Canton Basel-Stadt shares Legionella outbreak update

On Monday, August 3, canton Basel-Stadt confirmed in a press release that it was dealing with “an unusually high number of Legionnaires’ disease cases”. The canton’s Department of Health (Gesundheitsdepartement) reassured residents that the suspected source has been “identified and eliminated”. Further potential sources of infection are also being looked into.

A total of 26 Legionella cases have been confirmed in Basel. Nine people continue to receive inpatient treatment, seven required intensive care, one person remains in intensive care, and unfortunately one person has died.

Cooling towers shut down on Rebgasse following contamination

Basel-Stadt is focusing its investigations on cooling towers in central Kleinbasel, where tested facilities showed “exceedances of the limit for Legionella bacteria”. Evaporated water droplets from cooling towers may have contained the infection and, depending on the weather, spread and been inhaled by residents.

On Friday, July 31, authorities shut down two cooling towers located on the roof of the Manor headquarters on Rebgasse in Kleinbasel, and further investigations continue.

The Department of Health recommends consulting your doctor if you live in Basel-Stadt and develop suspected pneumonia. Symptoms include shortness of breath, fever and a severe cough.

What is Legionnaires’ disease and is it contagious?

Legionnaires’ disease is a type of pneumonia caused by the bacterium Legionella pneumophila. Infection happens when aerosolised water droplets containing the bacteria are inhaled.

The disease is not transmitted between people; rather, it spreads in water systems where the temperature is warm (between 25 and 45 degrees celsius) and where water is not frequently changed. The incubation period can range from two to 14 days.

Legionnaires’ disease can be transmitted in water pipes, faucets, showerheads, whirlpools and water cooling towers. According to the Basel-Stadt Department of Health, AC units and heat pumps used in Swiss homes are not impacted.

According to the Federal Office of Public Health (FOPH), reported by Watson, the number of Legionnaires’ disease cases in Switzerland has been on the rise since 2001. In 2025 alone, 529 suspected and confirmed cases were reported.