Legionella infections in Finland reached a record high in 2025, with more than 80 reported cases of legionella pneumonia, many linked to soil and compost products. Health authorities say this is the largest annual total ever recorded and marks a significant rise from roughly 50 cases in each of the previous two years.
The Finnish Institute for Health and Welfare and the Finnish Food Authority have noted that around half of those infected reported handling soil shortly before falling ill. Activities included changing potting soil, emptying compost, or working with garden growing media. Authorities have issued warnings about the risks posed by dry soil and compost, highlighting the need for careful handling.
Experts stress that legionella bacteria are naturally present in small amounts in fresh water and soil. Compost and other growing media can also harbor these bacteria. Infection occurs when bacteria are inhaled into the lungs, causing pneumonia. In some instances, the bacteria may enter the body through cuts or broken skin, though this is less common.
Riikka Ruotsalainen, a specialist at the Finnish Institute for Health and Welfare, said that the increase in reported cases may partly reflect more active testing and detection of the disease. She added that the rise mirrors trends seen in other Nordic countries, including Sweden, though the underlying reasons for soil-related infections remain unclear.
Authorities recommend practical precautions to reduce risk. People handling soil should open bags away from their faces, use low water pressure when moistening soil, wear gloves, and wash hands afterward. Cuts or abrasions should be covered, and FFP2 or FFP3 respiratory masks can protect against dust in situations where exposure is unavoidable. Soil products should be stored out of direct sunlight, since warmer conditions inside bags promote bacterial growth.
The risk of illness remains highest for older adults and individuals with weakened immune systems. Smoking and preexisting lung conditions also increase susceptibility. Healthy individuals are generally less likely to become ill from exposure.
Traditionally, legionella infections in Finland have been associated with water systems. The bacteria thrive in temperatures between 20 and 45 degrees Celsius and can grow in showers, hot tubs, humidifiers, and cooling systems. The recent spike linked to soil highlights an evolving public health concern that requires careful attention to gardening and composting practices.
