THL and the Finnish Food Authority warn about the legionella risk in soil products – record number of cases last year
A record number of cases of pneumonia caused by legionella bacteria were detected in Finland last year. The increase was mainly due to a rise in soil related infections.
More than 80 cases of Legionnaire’s Disease were identified in Finland in 2025. About half of the patients reported contact with soil or earth prior to falling ill. In the two preceding years, the total annual number of cases was around 50.
“An increase in soil-related infections has recently been observed not only in Finland but also in other Nordic countries, particularly Sweden. The reason for the rise is still unknown. Some of the increase may be explained by more active testing,” says Riikka Ruotsalainen, specialist at THL.
Legionella bacteria occur in soil and natural waters
Legionella bacteria are naturally present in small quantities in fresh water and soil. They can also be found in potting soil and compost products.
Exposure pathways in soil and earth related infections have varied. For example, patients may have changed potting soil or emptied a compost bin during the incubation period.
To prevent legionella bacteria from causing illness, dry soil and compost products should not be allowed to disperse dust into the air. If the bacteria reach the lungs, they can cause severe pneumonia. Infection may also occur through wounds in the skin.
The risk of falling ill is highest among older adults and people with weakened immune systems. Lung diseases and smoking also increase the risk. Most healthy individuals do not become ill even if they are exposed.
Tips to reduce the risk of infection when handling soil
When handling soil or compost products, it is advisable to follow these guidelines:
- Avoid creating dust clouds from soil or compost.
- Protect any wounds or broken skin.
- Use protective gloves and wash your hands thoroughly afterwards.
- Open soil bags so that the opening faces away from your face.
- Moisten soil or compost if needed using low water pressure, such as with a watering can.
- Clean soil or compost from tools using low water pressure.
- Store soil bags out of direct sunlight. The temperature inside a sun exposed bag is ideal for legionella growth.
- If dust cannot be avoided, FFP2 or FFP3 respirators provide protection. Fit the respirator tightly to your face.
The Finnish Food Authority reminds that consumers must be provided with sufficient information on the safe handling and storage of soil products in marketing materials. Manufacturers have been instructed to add safety guidelines to product packaging.
Water systems remain the most common source of legionella
Traditionally, water systems have been the most common source of legionella infections in Finland. Legionella bacteria thrive in temperatures between 20–45 °C and can grow in, for example, showers, hot tubs, humidifiers and cooling systems.
Legionella growth can be prevented by ensuring that cold water remains below 20 °C and hot household water stays sufficiently hot (at least 55 °C). Hot water refers to the water circulating in domestic hot water systems.
More information
Riikka Ruotsalainen
Specialist
THL
tel. +358 29 524 8158
[email protected]
Silja Mentula
Senior Researcher
THL
tel. +358 29 524 8161
[email protected]
Merja Torniainen
Senior Specialist
Finnish Food Authority
tel. +358 29 520 5077
[email protected]
