The Public Health Agency of Canada is partnering with provincial agencies in B.C., Alberta and Ontario to look into hundreds of gastrointestinal illnesses across Canada.
More than 200 illnesses related to the consumption of raw or undercooked B.C. oysters were reported in December and January.
143 of the cases were reported in B.C., 35 were in Alberta and 24 were reported in Ontario.
The government says norovirus contamination can occur when shellfish come into contact with sewage in water before being harvested.