KTUU News reports that four people infected with Campylobacter jejuni bacteria in south central Alaska were participating in a raw milk cow-share scheme at a Mat-Su Valley farm.

All four, who ranged in age from 1 to 81, became ill after drinking raw milk from one of the farm’s cows, and two said family members also experienced symptoms but did not seek medical attention, according to the news station. The confirmed cases of Campylobacter illness were reported from May 7 through June 4.

Alaska state law does not permit the sale of unpasteurized milk, but does allow owning shares of an animal to obtain raw milk — which does not have to be tested before it is distributed, said Alaska Department of Health and Social Services (DHSS) spokesman Greg Wilkinson.

Staff with the state Department of Conservation’s Division of Environmental Health visited the farm in May to evaluate sanitary conditions and pick up a bulk milk tank for testing. The sample tested negative for Campylobacter but positive for Listeria monocytogenes, another foodborne pathogen that can cause life-threatening infections in newborns and adults.

Officials believe the month-long pattern of cases points to a series of contamination events rather than a single bad batch, which is possible given the rich nutrients contained in milk that can encourage bacterial growth.

“Raw milk is an ideal substance for the proliferation of bacteria introduced through fecal contamination,” Dr. Joe McLaughlin, chief of the DHSS Section of Epidemiology, said in a news release. “Unpasteurized milk can be infected with a number of pathogens including Listeria, Salmonella, and as we’ve seen in this case, Campylobacter.”