Federal and provincial authorities are looking into the outbreak of gastrointestinal illnesses linked to the consumption of raw and undercooked oysters from B.C.

As of March 6, a total of 289 cases of gastrointestinal illness have been reported in three provinces: B.C., 201; Alberta, 40; and Ontario, 48.

The cases were reported between December last year and February 2017.

“The investigation into the cause(s) of the contamination is ongoing and complex,” stated a notice by the Public Health Agency of Canada on March 7. “Four shellfish farms where oysters are harvested in British Columbia have been closed for harvest at this time.”

According to the federal health agency, testing of several cases of gastrointestinal illnesses confirmed norovirus infection.

“Noroviruses are a group of viruses that can cause gastroenteritis in people, an illness that usually includes diarrhea and/or vomiting,” the agency noted. “Noroviruses are found in the stool or vomit of infected people. They are very contagious and can spread easily from person to person.”

The health agency advised that illnesses can be avoided by cooking oysters to an internal temperature of 90° Celsius or 194° Fahrenheit for a minimum of 90 seconds. It also recommended proper hand washing, and food safety practices.

People who are ill should drink plenty of liquids to prevent dehydration.