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What is Norovirus and what are the early symptoms?

People can get the Norovirus from contaminated food or water, and once infected can easily spread the disease to those around them directly or indirectly.

Norovirus outbreak in US and Canada linked to raw oysters
Lisa Maree WilliamsGetty

Authorities in Canada and the US are advising about a recent norovirus outbreak due to contaminated raw oysters from British Columbia. No recall has been issued for the US, but two Canadian distributors have decided to recall certain oyster products they sell in light of possible contamination.

Norovirus outbreaks are not uncommon, according to the CDC there are roughly 2,500 reported outbreaks in the US annually. Typically, they occur between November and April but can happen throughout the year. Anyone can get Norovirus, but children under age five, the elderly and those with weakened immune systems are more likely to have sever infections.

What is the Norovirus?

It is very likely that you will have a bout of Norovirus more than once in your life. Sometimes called the stomach bug or stomach flu, it has nothing to do with influenza virus, otherwise known as the flu.

Because there are many different types of noroviruses, getting infected by one does not necessarily grant immunity to another strain. Once you’ve been infected with one type of Norovirus you may develop immunity to that specific strain, but the length of time that protection lasts is unknown which explains why so many people of all ages get infected during outbreaks. There are those who are naturally unaffected by Norovirus due to their genetic makeup.

How do you catch Norovirus?

An outbreak can occur when a person ingests contaminated food or water. Noroviruses spread easily from one person who is infected to another as the infected person can shed billions of norovirus particles, but it only takes a few to get infected.

So direct contact with someone with the norovirus illness can result in infection or simply touching contaminated surfaces and then putting your hand in your mouth before washing.

What are the symptoms of Norovirus and how long before they appear?

Symptoms of norovirus infection generally appear within 12 to 48 hours after exposure to Norovirus. Most people will experience diarrhea, nausea, stomach pain and vomiting. You may also have body ache, fever and headache. The majority who contract norovirus illness will get better within one to three days.

However, young children, the elderly and those with compromised immune systems or other illnesses could experience severe illness. This could include having diarrhea and vomiting several times a day which could lead to dehydration.

Symptoms of dehydration according to the CDC include a decrease in urination, dry mouth and throat, and feeling dizzy when standing up. For young children, they may cry with few or no tears and be unusually sleepy or fussy.

The CDC advises that if you think you or someone you are caring for is severely dehydrated, to call your healthcare provider.

What have authorities said about the recent outbreak of Norovirus?

The FDA’s advisory on the recent norovirus outbreak links its source to raw oysters harvested in British Columbia as early as 31 January 2022, which consumers and retailers should find printed on product tags. The oysters in question were harvested in the south and central parts of Baynes Sound from areas BC 14-8 and BC 14-15.

They were shipped to 13 states including California, Colorado, Florida, Hawaii, Illinois, Maine, Minnesota, New Jersey, Nevada, New York, Oregon, Texas and Washington, as well as British Columbia and Ontario. However, they may have been distributed in other states, provinces and territories of the US and Canada.

The oysters contaminated with norovirus may look, smell, and taste normal, so authorities advise not serving raw oysters. The FDA recommends that restaurants and retailors return potentially contaminated oysters to their distributor for destruction or dispose of any products by throwing them in the garbage.

The two companies whose product has been linked to the outbreak have issued recalls for their affected oysters. They include Chef Creek Oysters from Stellar Bay Shellfish and Royal Miyagi oysters in the shell (Oyster N/Shell Royal Miyagi Ow) from Intercity Packers Ltd.


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