When several people fall ill from the same bacterium, the investigation becomes a race against time. The aim is to identify the source of infection as quickly as possible to contain the outbreak before more people become ill.
A new tool in the investigation of foodborne outbreaks is the platform SOFI (national Sequence-based surveillance Of Foodborne Infections).
“Foodborne outbreaks can be complex to investigate. The work involves multiple authorities, and effective collaboration is essential throughout the process,” says Camilla Thougaard Vester, Academic Officer at the DTU National Food Institute.
The platform allows the Central Outbreak Management Group, which coordinates the tracing of foodborne outbreaks in Denmark, to compare bacteria from patients, food and food production at the level of bacterial DNA. SOFI thereby enables faster and more reliable identification of infection sources.
The Central Outbreak Management Group consists of the Danish Veterinary, Food, Agriculture and Fisheries Agency, Statens Serum Institut and the DTU National Food Institute.
“The faster we can link patients and food, the faster we can determine the source of infection and warn the public if necessary. One of our strongest pieces of evidence is when we can find exactly the same bacterium in samples from patients and food,” says Head of Unit Susanne Schjørring from Statens Serum Institut, adding:
“SOFI contains data from both areas, which means we can establish direct links at the level of bacterial DNA without delay, even when the data have been generated by different authorities."
Investigation of foodborne outbreaks
The platform has contributed to the investigation of several major outbreaks described in this year’s report on zoonoses.
Salmonella Strathcona caused an international outbreak with at least 437 cases, including 29 in Denmark, and was linked to cherry tomatoes from Italy.
In September 2025, a Listeria outbreak in which 11 people fell ill and were hospitalised was rapidly linked through genetic analyses to ready-to-eat fish patties.
Investigations showed that Listeria bacteria found in patients were genetically identical to those found in the products, which were subsequently recalled.
“In connection with the Listeria outbreak mentioned, we quickly carried out an inspection visit at the suspected company. Samples collected during the inspection confirmed the presence of the bacteria in the production environment,” says Head of Unit Sørine Quaade Møller from the Danish Veterinary, Food, Agriculture and Fisheries Agency, and continues:
“With the new possibilities for comparing data via the platform, we have a stronger basis for targeting controls and preventive measures where they have the greatest impact.”
SOFI is owned and funded by the Danish Veterinary, Food, Agriculture and Fisheries Agency and Statens Serum Institut, and was developed with contributions from the DTU National Food Institute.
The Annual Report on Zoonoses compiles knowledge on diseases that can be transmitted between animals, food and humans, and is published by the DTU National Food Institute in collaboration with the Danish Veterinary, Food, Agriculture and Fisheries Agency and Statens Serum Institut
