The B.C. Centre for Disease Control has confirmed that an outbreak of illness related to eating uncooked Pacific Coast oysters is being caused by a norovirus.

The Canadian Food Inspection Agency is warning about eating raw oysters harvested from Effingham Inlet on Vancouver island. (iStock)The affected oysters have been traced to a section of Effingham Inlet on the west coast of Vancouver Island. The oysters were harvested between Sept. 7 and Sept. 21.

A health hazard alert by the Canadian Food Inspection Agency has been expanded to include oysters from Evening Cove Oysters Processing of Nanaimo, B.C.

Other processors already listed in the alert include Albion Fisheries of Victoria, Albion Fisheries of Vancouver, Pacific Rim Shellfish of Vancouver and Sea World Fisheries of Vancouver.

The Centre for Disease Control reports that at least three clusters of illness in the Vancouver area are related to eating uncooked oysters from Effingham Inlet.

Contaminated oysters were traced to a section of Effingham Inlet, on Vancouver Island. The number of people who have come down with gastrointestinal ailments is not being disclosed. Health officials say symptoms that include nausea, vomiting, diarrhea and stomach cramps usually occurred within 48 hours of consuming raw oysters, and lasted a couple of days.

Oysters feed by filtering large amounts of water through their gills. When the water is contaminated with norovirus, the virus can build up in the flesh of the oyster.

Norovirus — which can spread from person to person as well as through tainted food or in water contaminated by feces — is a common cause of gastroenteritis, but is rarely fatal. The virus is killed by cooking.