Ocean currents may have spread norovirus to B.C. oysters

The B.C. Centre for Disease Control says a norovirus outbreak that sickened more than 400 people may have been spread widely among West Coast oyster farms by ocean currents.

The outbreak forced the closure of 13 oyster farms on both the east and west coasts of Vancouver Island last fall.

Investigators were initially uncertain how a single source of illness could affect such a huge area, but researchers at the disease control centre say it's likely that contaminants spread by currents affected the oyster farms.  

Sewage is often the cause of ocean contamination, but an article in the British Columbia Medical Journal says it's still unclear if one or many sewage sources were involved. Some of the possible sources include raw sewage discharge from coastal towns, commercial fishing vessels and wastewater treatment plants.

A wet fall and unseasonably cold winter could have created ideal conditions for the norovirus to survive in B.C. waters.