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Norovirus infections are typically not reported to Public Health Ontario. However, outbreaks at hospitals, long-term care homes or child care centres are usually reported by local public health units.

Earlier this year, the shared that cases of norovirus were being reported more frequently in Ontario in 2024 than the last five years.

Canadian oyster recall

The issued a recall earlier this month for certain types of oysters contaminated with possible norovirus contamination.

The Dec. 21 recall includes certain Taylor Shellfish Canada ULC brands — some of which were sold in Ontario, Alberta and British Columbia.

An outbreak was first reported in British Columbia between Nov. 1 and Dec. 20, with 77 cases of norovirus-like illness reported in the Vancouver area.

“Oysters can become contaminated with norovirus that may be present in the marine environment where they are grown and harvested,” the .

“Regional health authorities are reminding the public of risks associated with consuming raw or undercooked oysters, especially those who may be at higher risk of severe illness such as children, older adults, people who are pregnant, or people who may be immunocompromised.”

What is Norovirus?

, or Norwalk virus, is a foodbourne illness that usually develops symptoms of gastroenteritis within 24 to 48 hours.

Other symptoms can include a low-grade fever, headache, chills, muscle aches and fatigue.

Most people who catch the virus will feel better after a day or two, without any long-term health effects.

Food contaminated with the virus may still look, smell and taste normal.

How is Norovirus spread? What to do if you get sick?

According to the , noroviruses are found in the feces or vomit of infected people. Aerosolized droplets in the air can infect someone nearby. It can also come from touching surfaces with the virus.

Outbreaks are seen mostly in nursing homes, schools, and daycares.

“There is no specific treatment, but drinking fluids is important to prevent dehydration,” the health unit said.

Drinking plenty of liquids to replace fluids lost from vomiting and diarrhea is particularly important for older adults, young children, pregnant people and immunocompromised people, the

In severe cases, patients may need to be hospitalized and given fluids intravenously.

How to prevent Norovirus

The Public Health Agency of Canada website advises you can protect yourself and your family from norovirus by following these precautions:

• wash your hands with soap and water:
• after using the washroom or changing diapers
• before preparing or eating food
• clean and disinfect surfaces after an episode of illness
• immediately wash clothing and linens that are soiled with vomit or diarrhea
• cook shellfish thoroughly before eating, especially oysters and clams
• wash raw fruits and vegetables thoroughly with clean running water before you prepare and eat them
• drink water from a safe (treated or boiled) water supply

If you’ve been diagnosed with a norovirus infection or suspect that you have one, you can help prevent the spread of illness by:

• Practising proper hand hygiene
• Not preparing or serving food or drink to others
• Not caring for others until three days after you recover
• Avoiding others until you are well again 

Shellfish study

The Canadian government recently collaborated with the U.S. to study , specifically molluscan shellfish — oysters, clams, mussels and scallops. 

The study concluded wastewater containing norovirus concentrations were being put back into the water from wastewater treatment plants, which in turn was exposing oyster-growing areas to the virus.