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Biological Health Hazard – Norovirus Outbreak, Mass Food Poisoning (shellfish): British Columbia, Canada

2017/02/20

NOROVIRUS – CANADA: (BRITISH COLUMBIA, ALBERTA, ONTARIO)
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Published Date: 2017-02-19 15:15:52
Subject: PRO/EDR> Norovirus – Canada: (BC, AB, ON)
Archive Number: 20170219.4850305

Date: Fri 17 Feb 2017 2:14 PM PT
Source: CBC News [edited]

An outbreak of norovirus linked to B.C. [British Columbia] – harvested oysters is now under federal investigation.

The Public Health Agency of Canada (PHAC) says it has taken on a leadership role in the investigation, now that cases have been reported in Alberta and Ontario, as well as B.C.

As of [Tue 14 Feb 2017], the agency says it’s aware of 221 reported cases of norovirus connected to B.C. oysters.

“We knew in November-December [2016] that there were cases popping up in B.C., but it wasn’t until the middle of January [2017] or so … that we started seeing or hearing about other cases in Ontario and Alberta,” said Mark Samadhin, director of PHAC’s outbreak management division.

“We know that it’s oysters from B.C., but beyond that, we don’t know what’s contaminated the oysters.”

Samadhin said local investigations are still being carried out by provincial health authorities, the Department of Fisheries and Oceans (DFO) and the Canadian Food Inspection Agency (CFIA), but PHAC has taken on a coordinating role in the investigations now that the outbreak is multi-jurisdictional.

Samadhin said oyster-related norovirus outbreaks of this scale are rare in Canada.

He said this outbreak does not seem to come from one particular source. He said the DFO and CFIA have shut down multiple farms for the short term after testing positive for norovirus.

Samadhin said that when oysters are contaminated with norovirus, it’s usually due to contact with untreated sewage, but the investigation has yet to prove the exact cause of the current outbreak.

Norovirus is a relatively common virus that can be contracted from many sources, Samadhin said – including those already infected, which can make it hard to find the original source.

“Those secondary transmission cases would’ve contracted the illness from somebody who was ill and not necessarily from direct contact with the food,” Samadhin said.

Keith Reid, owner of Odyssey/Stellar Bay Shellfish in Deep Bay, B.C., said his farm was closed for about a week-and-a-half while officials investigated before giving him the all clear.

Though his sales remain strong, Reid says outbreaks like this are troubling due to the difficulty in tracking down the source.

“There are so many things shellfish are exposed to before they’re finally eaten, so it’s really hard to trace exactly where this is coming from,” He said.

“It’s important as an industry that we put product into the marketplace where we’re confident that, no, this isn’t going to make you sick.”

Samadhin said the best way to avoid contracting norovirus from shellfish is to follow proper food safety practices.

This includes ensuring shellfish is cooked all the way through before eating it, keeping raw food separate from cooked food, and to wash your hands thoroughly – particularly if you’ve had contact with someone who is ill themselves.

Symptoms of norovirus include nausea, vomiting and diarrhea. (It’s the same virus that causes the “winter vomiting bug.”)

Samadhin said people generally recover from the illness in a day or 2 and often don’t seek medical attention.

But he said that if anyone gets sick after eating oysters, they should contact a health care provider and ensure that the case is reported to their local health authority.

PHAC’s full public health notice regarding the outbreak can be found on its website.

[Byline: Matt Meuse with files from Greg Rasmussen]

Communicated by:
ProMED-mail from HealthMap Alerts
<promed@promedmail.org>

[Mark Samadhin, director of PHAC’s outbreak management division, stated that he doesn’t think there is a single source, but it appears there may be a single supplier.

There also were norovirus outbreaks associated with oysters in 2016 in Canada. A notice was issued by Fisheries and Oceans Canada for the Subtle Islands, located east of Campbell River, B.C., after tests by the Canadian Food Inspection Agency found norovirus in oysters from the area. In addition, part of Clayoqout Sound on the west coast of Vancouver Island was also closed to shellfish harvesting in December 2016 after more than 100 people got sick from eating raw oysters in Tofino. [CBC 29 Dec 2016]

Norovirus can survive in marine water for long periods of time, although the virus does not multiply in that environment. Shellfish such as oysters, clams, and mussels are filter feeders and ingest norovirus if it is present in the water. Through filter feeding, oysters may concentrate the virus to much higher levels than might be found in the surrounding water. Potential sources of contamination include faulty wastewater treatment plants, failing septic systems, storm water runoff, dumping of boat sewage waste, and vomiting overboard near shellfish beds. Shellfish can be a source of norovirus illness, especially in colder months (November – March).

To prevent norovirus contamination, harvest shellfish only from open and approved areas. Cooking can reduce the risk of norovirus illness, but the virus can survive at temperatures up to 140 F [60 C]. Quick steaming or cooking until the shells just open is not enough to protect against norovirus illness. [Excerpted and edited from: http://www.doh.wa.gov/CommunityandEnvironment/Shellfish/RecreationalShellfish/Illnesses/Norovirus]

Additional reading: Y Yu et al. Molecular epidemiology of oyster-related human noroviruses: Global genetic diversity and temporal-geographical distribution from 1983 to 2014. Appl. Environ. Microbiol. 28 August 2015. doi:10.1128/AEM.01729-15
-Investigators examined DNA of 1077 samples of norovirus in oysters. They found 80 percent of documented human noroviruses and saw a match in the oysters, most of which were found along coasts contaminated by human sewage. More unsettling, oysters act as incubators for the virus to mutate between outbreaks. Raw oysters seem to be especially dangerous transmitters [of norovirus]. – Mod.LK

A map of Canada can be found at http://healthmap.org/promed/p/12

A HealthMap/ProMED-mail map can be accessed at: http://healthmap.org/promed/p/12.]

See Also

Norovirus – Germany, UK (England) 20170127.4797915

2016
—-
Gastroenteritis: Greece, UK (England) 20161231.4734849
Norovirus – USA (02): (Chicago) 20161217.4705776
Gastroenteritis – Australia: norovirus, new strain 20161004.4529481
Norovirus – Italy (02): (SC) waterborne susp 20160722.4362934
Norovirus – Italy: (SC) waterborne susp 20160722.4360244
Norovirus – USA: (OH) political convention 20160720.4357183
Undiagnosed illness – Canada (02): (ON) norovirus susp. summer camp, children 20160710.4336375
Norovirus (02): cruise ship UK to USA, USA to Cuba, Disney line 20160510.4212873
Norovirus – Spain (02): (CT) bottled water 20160427.4186835
Norovirus – Philippines: (ZAS) 20160427.4186834
Norovirus – Spain: (CT) bottled water 20160419.4170111
Norovirus: prolonged viral shedding post infection, research 20160111.3927380
Norovirus – China: (GD) 20150409.3287755astroenteritis: Greece, UK (England) 20161231.4734849
Norovirus – USA (02): (Chicago) 20161217.4705776
Gastroenteritis – Australia: norovirus, new strain 20161004.4529481
Norovirus – Italy (02): (SC) waterborne susp 20160722.4362934
Norovirus – Italy: (SC) waterborne susp 20160722.4360244
Norovirus – USA: (OH) political convention 20160720.4357183
Undiagnosed illness – Canada (02): (ON) norovirus susp. summer camp, children 20160710.4336375
Norovirus (02): cruise ship UK to USA, USA to Cuba, Disney line 20160510.4212873
Norovirus – Spain (02): (CT) bottled water 20160427.4186835
Norovirus – Philippines: (ZAS) 20160427.4186834
Norovirus – Spain: (CT) bottled water 20160419.4170111
Norovirus: prolonged viral shedding post infection, research 20160111.3927380

2015
—-
Norovirus update (03): USA (MN, CA) new strain (MN), RFI 20151228.3896625
Norovirus – middle & high income countries: elderly, retrospective studies 20151019.3724752
Norovirus update (02): Italy, novel Kawasaki strain 20150904.3622339
Gastroenteritis – Macedonia: Dutch-holidaymakers, norovirus susp. 20150819.3589707
Gastroenteritis – USA (PA) Cowans Gap, norovirus 20150729.3545782
Norovirus update (01) 20150724.3534291
Norovirus – China: (GD) 20150409.3287755
………………………………………….sb/lk/ec/jh

Source:
A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases


Related

TV: Shellfish disappearing along west coast, nobody knows why — Has become systemic crisis — Finding Pacific shellfish ‘next to impossible’ — Manager: “Recently there’s no local scallops at all, supply gone” — Chef: Began a few months ago, oyster farms flourishing for years all of a sudden had to shut down (VIDEOS) February 8, 2015

Massive die-off of oysters and scallops in Pacific Northwest: “Millions of shellfish dying” — Never seen anything like it — “By July mortality hit 95 to 100 per cent” — “Deformed shells, smaller in size” — “Cause is unknown, but ocean acidification is main suspect” (AUDIO) February 28, 2014

Infection from Consumption of Raw Shellfish or Marine-Related Wounds

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