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14/05/18: Norovirus likely from sewage discharge during herring run

Herring-Eggs-406x288 (1)

Herring eggs

Public health officials on Vancouver Island, off Canada’s Pacific Coast, suspect that the likely source of a norovirus outbreak associated with the March herring run was from untreated sewage associated with marine operations.

Untreated sewage also was blamed for shellfish farm closures in Baynes Sound this year.

But the Public Health Agency of Canada, working with provincial public health partners in investigating the Norovirus outbreak, noted that the precise cause of the contamination has not been identified.

“There are a number of potential risk factors, one of which is the herring fleet in Deep Bay,” said Greg Thomas, executive director of the Herring Conservation and Research Society.

“In pre-season meetings with the herring industry advisors, DFO (Department of Fisheries and Oceans) reviewed the issue of contamination in Baynes Sound and prohibition on sewage discharge nearshore,” Thomas told Victoria News.

Dr Paul Hasselback, medical health officer for Central Vancouver, told the newspaper the outbreak was caused by a single genotype that has not been seen in community-based illness in British Columbia since 2012. That led Hasselback to suggest the outbreak probably did not come from a land-based domestic source.

“It appears probable that the event was caused by a single contamination event likely around the time of the herring fishery,” he said in a letter to the Regional District of Nanaimo. “There is a strong suspicion that the event may be associated with untreated sewerage contamination associated with marine operations.”

The herring run happened in March when the presence of Vibrio Cholera was found in herring egg samples taken from the area of French Creek and Qualicum Bay after four people got sick after eating them. The Department of Fisheries and Oceans closed the area for the harvesting of herring eggs.

While investigations into the presence of Vibrio Cholera continue, Hasselback noted that it is most likely that that organism is naturally occurring in marine waters and unrelated to human sewage.

In April, federal officials closed two shellfish farms due to the outbreak of Norovirus. Health authorities have reported about 40 cases of the acute gastrointestinal illness since early March.

Dumping raw sewage by vessels is against the law and regulated by Transport Canada, but local officials say the agency is unable to fully enforce the law.

Noroviruses cause acute gastroenteritis, sometimes thought to be stomach flu. This is not influenza or the flu, which is a respiratory infection caused by the influenza virus, Island Health said.

Norovirus outbreaks occur in British Columbia each year and are common in long-term care homes, daycare centres, schools, hospitals and on cruise ships, the health agency said.

The virus can be spread among people who do not wash their hands, or if someone with the illness handles food, water or ice. Norovirus can also be found in the vomit and diarrhoea of people who are sick.

Symptoms usually appear within 24 to 48 hours after exposure to the virus. There is no vaccine to prevent it and no treatment for the illness, but most people recover in two or three days.

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