Vancouver Coastal Health has ordered restaurants to stop serving raw oysters from local waters in response to a rising tide of foodborne illness caused by vibrio parahaemolyticus, a bacteria that naturally occurs in shellfish.

According to an advisory issued Wednesday, 31 cases connected to raw oysters have been reported in B.C. so far this year, although the actual number is likely much higher because not all cases are reported.

Symptoms include diarrhea, cramps, vomiting and fever that can last up to a week.

VCH has ordered restaurants to cook all B.C. oysters and said only oysters from outside the province can be served raw. The order comes as the BC Centre for Disease Control issued a similar warning asking consumers to avoid eating locally harvested oysters raw.

“Normally we see between eight and 10 cases in (June and July),” said Marsha Taylor, an epidemiologist with the BCCDC. “So there has been a really notable increase this year.”