In 2022, there were 86 recorded cases of listeria, which is the highest number since 2014 with 92 cases. It is a significant increase relative to last year with 62 recorded cases and 2020 with 43 recorded cases. In 2022, the Central Outbreak Management Group investigated three major listeria outbreaks that accounted for a third of all recorded cases in 2022.
These are the findings presented in the annual report on the occurrence of zoonoses - animal and foodborne diseases that can be transmitted to humans prepared by the National Food Institute, Statens Serum Institut, and the Danish Veterinary and Food Administration. These three organizations make up the Danish national food safety contingency response team and are jointly responsible for investigating outbreaks of foodborne diseases in the Central Outbreak Management Group.
“Listeria is one of the foodborne bacteria we monitor particularly closely, as it can cause a serious infection with blood poisoning or meningitis in already weakened people and pregnant women. In 2022, we found the source of two major outbreaks,” says epidemiologist Luise Müller from Statens Serum Institut.
“All outbreaks have been reviewed to find genetic matches. We can therefore say with great certainty that the tracing showed that two of the outbreaks were caused by infected fish cakes and sliced meat roll, respectively,” says Head of Research Group and Senior Researcher Marianne Sandberg from the National Food Institute.
Difficult to combat
Listeria is a highly resistant bacterium. A survey among 20 food companies shows that listeria was found to almost the same extent at four years’ interval, despite the Danish Veterinary and Food Administration having done much work in the intervening period to prevent the problems through campaigns aimed at the companies. Listeria was found in 43 per cent of the companies in 2016 and in 32 per cent in 2020.
The Danish Veterinary and Food Administration has therefore launched a number of new measures.
“The Danish Veterinary and Food Administration has, among other initiatives, introduced additional inspections and sampling at companies that have had listeria-containing products recalled. When investigating an outbreak, we invite the affected companies to a dialogue with exchange of data and other information,” says Annette Perge, Head of Section at the Danish Veterinary and Food Administration.
Products can be made safer
In connection with the major outbreaks in 2022, many people became ill within a short period, which indicates that listeria was massively present in the products when they were sent out to the market from the companies. Listeria bacteria can hide for several years, for example in biofilm in the machines, which can be difficult to clean.
“One measure that can safeguard ready-to-eat products such as sliced meat roll and other cold cuts against high numbers of listeria bacteria may be to stabilize the product by ensuring the right combination of product properties and storage conditions, so that listeria can no longer grow during the shelf life of the products. A number of tools have been developed that can help the industry find the right combination,” says Professor and Head of Research Group Lisbeth Truelstrup Hansen from the National Food Institute.
How to avoid listeria?
Elderly people, people with impaired immune systems, and pregnant women should pay special attention when eating cold cuts and cold-smoked fish - it should be as fresh as possible. The temperature in the refrigerator must not exceed 5°C, and soft cheeses made from unpasteurized milk should be avoided.
Learn more
The Annual Report on Zoonoses presents a large amount of the collected data on the occurrence of zoonoses in feed, animals, food, and humans by the Danish authorities and industry. The report contains data spanning more than ten years and thus makes it possible to follow trends over time.
The report has been published by the National Food Institute and prepared in collaboration with Statens Serum Institut and the Danish Veterinary and Food Administration. The first Annual Report on Zoonoses was published in 1998.
Read the full report on the National Food Institute website: Annual Report on Zoonoses in Denmark 2022 (pdf)
The electronic file has been amended 18. July 2023, as a few minor errors were identified in the printed version published 21. June 2023.
See reports from previous years on the DTU National Food Institute website.
Contact
Head of Section Annette Perge, Danish Veterinary and Food Administration, tel. +45 72 27 65 92, email ape@fvst.dk,
Epidemiologist Luise Müller, Statens Serum Institut, tel. +45 32 68 85 90, email lum@ssi.dk
Professor and Head of Research Group Lisbeth Truelstrup Hansen, National Food Institute, tel. +45 20 64 06 77, email litr@food.dtu.dk
