Increased severity of two concurrent Campylobacter jejuni clones causing large outbreaks, Denmark, July to October 2025.

In July-October 2025, two concurrent Campylobacter jejuni outbreaks (clones ST49#3 and ST52#4) with 112 notified cases were detected through Denmark's whole genome sequencing surveillance programme. The outbreaks were clinically severe: 45 (40%) infected individuals were hospitalised and 16 (14%) had bacteraemia. We estimated 900 laboratory-confirmed outbreak cases. Both outbreaks originated from Danish-produced chicken meat. These outbreaks reveal the vulnerabilities in the current prevention and control framework given by the regulatory tolerance for Campylobacter in fresh poultry meat.