There’s an old saying that you should never eat raw oysters in a month that doesn’t contain an “R” in its name. There is some truth to this, particularly this summer.
Oysters are harvested off BC’s coastal waters, and seem to be increasingly popular, particularly in the summer. Yet raw oysters can cause illness and outbreaks, mostly due to norovirus. Norovirus is a pathogen found in human feces – so how does it get into the oysters? Oysters are filter-feeders, filtering vast quantities of ocean water and concentrating any organisms, including norovirus, found in those waters. Careful handling and storage after harvesting can’t prevent this type of contamination.
You may have seen this advisory in restaurants in our region:
“The consumption of RAW oysters poses on increased risk of foodborne illness. A cooking step is needed to eliminate potential bacterial or viral contamination.” -Medical Health Officer
This summer though, we are seeing more people getting sick by eating raw oysters, there is actually an outbreak of Vibrio parahaemolyticus. Vibrio parahaemolyticus is naturally occurs in BC coastal waters (not caused by human feces) and can contaminate oysters, which can make people sick if they eat it. This illness can be nasty – watery diarrhea, cramps, vomiting and fever. It can last up to a week.
30 people in our region have had it this summer, that we know of. And since most cases of foodborne illness are not reported to us, this is likely the tip of the iceberg.
Vibrio parahaemolyticus concentrations are associated with water temperatures, as they thrive in warmer waters. So it should be no surprise that in 2015, with climate change a reality, coastal waters are even warmer and Vibrio parahaemolyticus is again a concern.
This is likely a problem that is here to stay in the summer months. So what should you do if you love oysters? Eat them grilled. Or, if you really crave raw oysters, ask for east coast oysters, where water temperatures are cooler and Vibrio has not been reported.