In August 2016 local and public health officials in Colorado investigated an outbreak of Campylobacter jejuni infections among persons who consumed raw (unpasteurized) milk from the same herdshare dairy. Illness onset dates ranged from August 8, 2016 to September 16, 2016. Pulsed-field gel electrophoresis (PFGE) patterns for 10 cases with available isolates were indistinguishable. In addition, two milk samples (one from the dairy and one obtained from an ill shareholder) also tested positive for the outbreak strain. Among 91 (53%) of 171 shareholder households that responded to requests for follow-up interviews, representing 207 persons in 5 or more Colorado counties, 12 confirmed and 5 probable cases were identified. One hospitalization occurred. There were no deaths.

Five C. jejuni isolates sent to the CDC for antimicrobial susceptibility testing were resistant to ciprofloxacin, tetracycline, and nalidixic acid.