FERNDALE — Five people were sickened by the bacteria found in raw milk that was recalled last month from a local dairy, the Whatcom County Health Department announced Monday.

Four Whatcom County residents and one Skagit County resident tested positive for the same campylobacter jejuni strain that was found in a routine sample of raw milk from Pleasant Valley Dairy. The dairy pulled that batch of milk from the shelves and has resumed its distribution of raw milk.

The dairy has changed its testing procedures to reduce the risk of releasing contaminated milk, the health department said.

Campylobacter is the most common bacterial cause of diarrhea in the U.S., the department said. The county averaged 52 cases per year between 2002 and 2006.