More than 100 people are sick in a Campylobacter outbreak in Denmark linked to a local dairy.

The Danish Veterinary and Food Administration (Fødevarestyrelsen), DTU Food Institute and Statens Serum Institut (SSI) are investigating illnesses that began in Bornholm in late May.

Patient interviews point toward pasteurized milk from Bornholms Andelsmejeri (Bornholm Dairy) as the source of infection but product testing has been negative for Campylobacter. Bornholm Dairy is a cooperative owned by Bornholm milk producers.

From May 28 to June 5, 107 people living on Bornholm or who recently visited the island have tested positive for Campylobacter jejuni. The alarm was first raised by Bornholms hospital and at least 16 people needed hospital treatment after Pentecost, a Christian holiday. Patients range in age from 9 months to 97 years old including 45 females and 62 males.

SSI contacted patients and asked them what they ate and drank before becoming ill. The agency also interviewed a control group of healthy citizens. Answers on what 34 patients ate and drank were compared with responses from 68 healthy people living in Bornholm. A total of 32 of the 34 cases drank milk while 45 of 68 controls had this exposure.

The outbreak peaked in late May. Authorities believe it is an isolated incident and that there are no products still on the market that could make people sick.

Campylobacter is the top cause of gastrointestinal infection in Denmark. In 2019, more than 5,300 cases were registered, which is the highest number ever recorded.

Negative product testing
The Danish Veterinary and Food Administration (DVFA) took samples from milk but no traces of Campylobacter have been found.

“It hasn’t been possible to find Campylobacter in the milk so we don’t have the physical proof. We took samples from four days of production, each day when they do a production they take out some reference samples and put them in the fridge and store them for a few days,” said a DVFA spokesman.

“So when we heard about the problem we tested the reference samples and there was no Campylobacter in them. It might be because it is a low concentration. Another possibility is a problem in production that has already taken place. In the coming weeks other channels will be examined, it could be in the water or in the milk producing animals.”

The spokesman said only milk and not cheese is affected but declined to answer a question on the distribution of potentially contaminated milk.

The dairy has stopped producing to do a technical review of production equipment and cleaning, according to the DVFA.

A statement from the company said no Campylobacter has been found in dairy products, the plant is clean and free of defects, and that all lawful procedures have been followed. It added there was no possibility that pasteurized milk could be mixed with the unpasteurized milk.

All consumer products analyzed from May 26 onward have not revealed any Campylobacter and site inspections by authorized external service engineers and DVFA did not find any issues.

People with Campylobacter infection usually get diarrhea, fever, and stomach cramps. They may also have nausea and vomiting. These symptoms usually start two to five days after the person ingests Campylobacter and last about one week.