More than half a dozen people have been infected with listeria in Denmark since August.
Between August 21 and October 24, the Staten Serum Institute (SSI) reported seven people infected with the same type of Listeria monocytogenes.
Five men and two women fell ill. The age of patients ranges from 75 to 99 years, with an average of 84 years. Four patients are from Hovedstaden, two from Siddanmark and one from Sjælland.
The National Food Institute of the Technical University of Denmark, the Danish Veterinary and Food Administration (Fødevarestyrelsen) and SSI are investigating the outbreak.
SSI is responsible for whole genome sequencing (WGS) of Listeria isolates from patients and interviews with them or their relatives to try to determine the possible source of infection.
WGS of Listeria monocytogenes bacteria isolated from patients shows that they are very closely related and belong to the sequential type 403. This suggests a common source of infections.
Outbreak update
SSI also updated the number of people sick from another listeria outbreak.
It was previously known that five people fell ill. However, there are currently 11 patients registered between August 13 and October 24.
The patients were five men and six women. They range from 30 to 95 years old, with an average age of 75 years. Five cases have been reported in Sjælland, three in Nordjylland, two in Juddanmark and one in Midtjylland.
An investigation into the outbreak found that fishcakes were the cause of the illness. Comparison of patient samples and product samples showed that the bacteria were identical.
Tenax Sild A/S, which produced the fish cakes, recalled them from stores in September after Listeria monocytogenes was discovered. Expiration date: October 10, 2025
WGS of bacteria isolated from patients showed that they are closely related and belong to sequence type 7.
It can take up to 70 days after exposure to listeria for symptoms of listeriosis to develop. Symptoms may include vomiting, nausea, persistent fever, muscle pain, severe headache and neck stiffness.
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