Potentially hundreds sick in Danish Campylobacter outbreaks

Danish public health officials have reported two outbreaks and a general increase in Campylobacter cases.

Since July, two outbreaks of Campylobacter jejuni have been registered at the Statens Serum Institut (SSI). Half of the patients in both outbreaks have been hospitalized. Only a small proportion of cases are subtyped, which means the actual number of people ill in outbreaks is likely much higher. SSI said the outbreaks may include several hundred patients.

Campylobacter is the top cause of bacterial infections in Denmark. Since the end of July, more cases have been reported compared to the same period in previous years.

The two outbreaks have 20 and 12 patients, respectively. Those sick are 19 men and 13 women. Patients are between 2 and 89 years old and live in different parts of the country.

The outbreaks are being investigated by the National Food Institute at the Technical University of Denmark, Danish Veterinary and Food Administration (Fødevarestyrelsen), and SSI.

SSI is responsible for whole genome sequencing Campylobacter isolates from patients and the Danish Veterinary and Food Administration leads the examination of samples from products and the environment. Positive human samples are compared with any positives from products and the environment.

In 2024, seven of 10 Campylobacter outbreaks were linked to chicken meat. A total of 5,546 cases were reported, up from 5,186 in 2023.

Danish action plan
The Campylobacter action plan, developed by the Danish Veterinary and Food Administration, industry groups, and the National Food Institute, aims to reduce human infections and focuses on lowering prevalence of the bacterium in chickens and chicken meat, the primary source of transmission.            

“The technological advances of recent years, including whole genome sequencing, enable quicker identification of both sources of infection and new preventive methods,” said Brian Lassen, senior researcher at the National Food Institute.

“At the DTU National Food Institute, our research is particularly focused on reducing Campylobacter in organic and free-range flocks, although several of the methods can also be applied to conventional flocks.”

Projects by the National Food Institute are aimed at limiting Campylobacter in production and improving risk assessments. Research ranges from feed additives and cooling technologies to advanced packaging solutions, whole genome sequencing, and machine learning for source attribution and outbreak tracing. 

The action plan also includes information for consumers.

“As a consumer, you can take steps yourself to avoid Campylobacter infection. Remember good kitchen hygiene practices – in particular, keep raw meat separate from ready-to-eat foods, and ensure chicken meat is thoroughly cooked,” said Sørine Quaade Møller, from the Danish Veterinary and Food Administration.

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