The Public Health Agency of Canada (PHAC) said Thursday recalls of B.C. oysters have been issued on four dates since March 18, and that more could be issued.
Some oyster harvesting areas on the B.C. coast have also been closed as federal and provincial health and food inspection officials investigate.
The bulletin did not state which areas have been closed, but the recalls were related to harvest areas 14-15 and 14-8, located between Denman Island and Vancouver Island.
Most of the norovirus cases linked to the outbreak (262) were reported in B.C., however cases have also been documented in Alberta, Saskatchewan and Ontario. No deaths have been reported.
Source of B.C.-based norovirus outbreak traced
Earlier this month, Vancouver Coastal Health issued its own raw B.C. oyster warning, after linking 50 cases to the shellfish.
Norovirus can create severe gastrointestinal distress, with symptoms that include diarrhea, vomiting, nausea and stomach cramps. PHAC says symptoms usually develop within 24 to 48 hours of consuming the affected product. Symptoms pass for most people within a day or two and suffer no lasting health effects.
People who are pregnant or have compromised immune systems, along with young children and the elderly are at a higher risk.
Anyone with severe symptoms should contact their health-care provider.
The public is being urged not to eat any of the recalled oysters, and to avoid eating any raw or undercooked oysters.
Oysters should be cooked to an internal temperature of 90 C/ 194 F and for a minimum of 90 seconds before eating, according to PHAC.
B.C. saw another norovirus outbreak linked to raw oysters in 2016 and 2017, which sickened an estimated 400 people across Canada.
Researchers with the B.C. Centre for Disease Control later linked that outbreak to norovirus in sewage carried by ocean currents, along with colder-than-usual weather that helped the virus survive.
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