Authorities in Finland are investigating a Listeria outbreak that has affected eight people.

All patients have been hospitalized but no deaths have been recorded. The age range of those sick is 60 to 93 years old, five are female and they live in different parts of the country.

Ruska Rimhanen-Finne, a veterinary epidemiologist at the National Institute for Health and Welfare (THL), said all illnesses occurred within a month in May and June.

“At the moment, we have several listeriosis clusters under investigation, but the others are long-term clusters with cases within several years,” she told Food Safety News. “We encourage the local authorities to interview the patients as soon and thoroughly as possible by using an online questionnaire that is readable at THL in real-time. We compare the interviews in order to find common exposures.

“We also encourage the local authorities to go through foods in patients’ homes and test risky foods for Listeria. The Finnish Food Authority (Ruokavirasto) types Listeria strains from foods that have been tested in April and May in order to find similar strains as in patients. We also check if we can use patients’ purchase information to find common exposures.”

Below 100 infections per year
The Multilocus sequence typing (MLST) 6 cluster is being investigated with the help of whole genome sequencing. The THL is not aware of similar cases in other countries.

Finland has between 40 and 90 listeriosis cases annually. Listeriosis is an infectious disease caused by the bacterium Listeria monocytogenes. Symptoms include fever, muscle pain, septicemia (blood poisoning) and meningitis. The incubation period is usually one to two weeks but can vary between a few and 70 days. The elderly, pregnant women, newborn infants and people with weak immune systems are more susceptible to infections.

High risk foods include pre-packed sandwiches, deli and ready-to-eat meat products such as cooked, cured and/or fermented meats and sausages, soft cheeses and cold smoked fishery products.

Between March and May, four suspected foodborne outbreaks were reported in the country, compared with an average of 18 in previous years, according to the THL.

The agency believes this is because of the coronavirus pandemic and associated limitations and recommendations. When hands are washed and food prepared for smaller groups, there are fewer epidemics. Suspected pathogens in the four outbreaks were Campylobacter, Yersinia, and norovirus.