Oysters are officially to blame for a norovirus outbreak that originated in Tofino last month.
“We do know of at least 120 people who became ill with norovirus and it was because of exposure to raw oysters,” Island Health Officer Dr. Paul Hasselback told the Westerly News on Monday.
The Department of Fisheries and Oceans Canada shut down all shellfish harvesting in a portion of Lemmens Inlet last week and Hasselback suggested further closures could be coming.
“The investigation isn’t quite complete. There are some loose ends and there may be further actions,” he said. “We can’t put every oyster back exactly where it came from but, believe it or not, we can actually track lots of oysters as to where they were processed, harvested and transported and that’s all been part of this investigation.”
Oysters were the primary suspect in Island Health’s investigation from the onset as roughly 30 reports of norovirus cases came in in the immediate aftermath of Tofino’s Clayoquot Oyster Festival.
Hasselback said the number of reported cases ballooned from 30 to 120 after anyone who became sick after attending the festival was encouraged to report in.
“We certainly did get individuals who had consumed the product in Tofino that had gone to other provinces, or even south of the border, who were notifying us of illness so it’s good to know that the communication channels worked well,” he said.
He said the oysters were likely contaminated before arriving at the Oyster Festival’s tables.
“The investigation strongly suggests that the oysters were already contaminated with norovirus before they came to any of those locations so there was nothing that the festival people or other locations would have had any control over or would have known about,” he said.
“Unfortunately we don’t have easy lab testing for things like viruses that would make it simple to screen the product before it gets out and then we end up finding out afterwards that potentially was contaminated.”
He said he has spoken with festival organizers to hash out strategies for next year.
“It was a great time and people want to come back and, if we can make it safer, that would be a wonderful thing to do,” he said.
He doubted any risk remains and added the “vast majority” of reports came in prior to Nov. 21 and none have come in since Nov. 26.
“This event happened over a month ago and we’re fairly confident that the investigation precluded distribution of additional oysters that resulted in these events,” he said.
“We’ve been monitoring locally, provincially and nationally looking for other clusters of norovirus that might be associated with oysters, so there’s nothing to suggest that oysters are making other people sick at this point in time.”
He added, though, that consuming raw oysters is always a dice-roll.
“Raw oysters might taste good and for the most part are safe, but they can be a source of a variety of illnesses,” he said. “This is just another example of one of the concerns about eating raw oysters.”
He said the recent Tofino outbreak is the largest norovirus cluster he’s seen in the past five years but noted it was not unprecedented.
“We have seen it before,” he said. “We know this can occur.”
While grossly debilitating, norovirus rarely brings more than a few days of discomfort, according to Hasselback.
“One of the reassuring things is that norovirus, for the most part, is an annoyance. It causes vomiting, nausea and diarrhoea for 24-48 hours and almost all people recover from it and bounce back,” he said. “It’s a loss of a couple of days because of a really yucky illness, but rarely results in complications or severe illness and we’re certainly not aware of any such problems having occurred amongst anybody associated with this particular event.”
Hasselback encourages anyone who becomes sick after eating at an event or restaurant to report their illness immediately.
“That initiates a series of investigations just to see if there’s anything thats a pattern developing,” he said. “We’re always happy to look into individual complaints.”