In May 2012 Minnesota and Wisconsin public health and agriculture officials investigated an outbreak of Campylobacter jejuni among members of a 5th grade class who visited a farm school located near Glenwood City, Wisconsin. During the trip which took place between May 9-11, a 5th grade teacher purchased raw milk at a farm the group visited. The teacher shared the milk with students and teachers in his class as well as with his 6 year old son.

Investigators interviewed adult chaperones, teachers and students present on the trip. Seven persons met the case definition. All 7 cases reported diarrhea and cramps. Six of the 7 cases consumed raw milk. The median incubation period was 6 days (range 3 to 10 days). One person sought medical care. No one was hospitalized and no one died.

Two cases submitted stool samples for laboratory testing. Both were culture positive for Campylobacter jejuni. Raw milk samples collected at the farm also tested positive for C. jejuni. Isolates of C. jejuni from both cases and the raw milk were indistinguishable by PFGE, Minnesota subtype designation CMP31.