Legionellosis Cases Rising in Switzerland, Particularly in Ticino and Valais

Legionellosis, a respiratory disease caused by Legionella bacteria, is experiencing a rise in cases across Switzerland, with the cantons of Ticino and Valais reporting the highest numbers of new infections in 2024. The disease, contracted through inhaling contaminated water droplets, can lead to pneumonia and requires prompt medical attention.

Current Situation in Switzerland

According to data published at the start of 2024, approximately 25 cases of legionellosis were reported in the canton of Valais, mirroring figures from the previous four years. This translates to an incidence rate of 6.5 cases per 100,000 inhabitants. Valais’s incidence rate places it within the mid-range for French-speaking cantons, all of which maintain rates below 8 cases per 100,000 inhabitants.

However, the canton of Ticino is experiencing a more significant impact. In 2024, Ticino recorded 58 new cases, resulting in an incidence rate of 13.9 cases per 10,000 inhabitants – a notably higher figure than other regions.

Understanding Legionellosis

Legionella bacteria are naturally present in freshwater environments, but can proliferate in human-made water systems, such as cooling towers, hot water tanks and plumbing systems. Infection occurs when individuals inhale aerosolized water containing the bacteria.

Symptoms of legionellosis typically include:

• Fever
• Cough
• Shortness of breath
• Muscle aches
• Headache

In severe cases, legionellosis can lead to severe pneumonia, respiratory failure, and even death. Individuals at higher risk include those with weakened immune systems, chronic lung disease, and smokers.

Public Health Response

The Federal Office of Public Health (FOPH) is dedicated to the health of the Swiss population and is responsible for national healthcare policy [FOPH Website]. The FOPH monitors public health threats and provides guidance to cantons and healthcare providers. The FOPH also monitors radioactivity in the environment, including at a high-altitude station on the Jungfraujoch [FOPH Website].

Wastewater-based epidemiology (WBE) is being used to monitor the spread of pathogens, including SARS-CoV-2 and influenza viruses, in wastewater treatment plants in the Ticino region [ARIS SUPSI]. This approach can help track disease outbreaks and inform public health interventions.

Prevention and Mitigation

Preventing legionellosis involves maintaining and disinfecting water systems to prevent bacterial growth. Key preventative measures include:

• Regular cleaning and disinfection of water tanks and cooling towers.
• Maintaining appropriate water temperatures.
• Properly designing and maintaining plumbing systems.

Individuals can reduce their risk of exposure by avoiding inhaling aerosols from potentially contaminated water sources.

Looking Ahead

The FOPH continues to monitor the situation and provide updates as needed. Ongoing surveillance and preventative measures are crucial to controlling the spread of legionellosis and protecting public health in Switzerland. As respiratory infections, including those caused by flu viruses and RSV, remain a concern, continued vigilance and preventative measures are essential [FOPH Website].