Public Health Notice - Outbreak of gastrointestinal illnesses linked to raw and undercooked oysters
While Canada's food supply is generally very safe, sometimes the food we eat may carry viruses that can make us sick, like noroviruses.
What are noroviruses?
Noroviruses are a group of viruses that cause gastroenteritis in people, an illness that usually includes diarrhea and/or vomiting. People often call gastroenteritis the flu, though it is in no way related to the influenza virus, which causes respiratory illness.
Noroviruses are common in North America and are very contagious, affecting all age groups. Norovirus illness can happen year-round, but outbreaks are more common in fall and winter months. The illness is easily spread in group settings where people are in close contact, like schools, hospitals, childcare facilities, nursing homes, cruise ships, and passenger trains.
The term "norovirus" was approved as the official name for this group of viruses in 2002. Previously, they were called Norwalk-like viruses, as norovirus was first identified as a virus in 1972 after an outbreak in Norwalk, Ohio.
How do people get sick?
Noroviruses are found in the stool or vomit of infected people. They are very contagious and can spread easily from person to person. People infected with norovirus can be contagious from the moment they start feeling ill to at least three days after they have recovered. Some people may be contagious for as long as two weeks after recovery.
People can become infected with the virus in several ways:
- through direct contact with another infected person (for example, when caring for or diapering an ill child, or sharing food or utensils with an ill person)
- by touching surfaces or objects contaminated with norovirus
- by eating food or drinking water that has been contaminated
Most foodborne outbreaks of norovirus illness likely happen when food is contaminated by food handlers who have the virus, especially if they do not wash their hands properly after using the bathroom. Some foods can be contaminated at their source (for example, shellfish like oysters may be contaminated by sewage in water, before they are harvested). Waterborne outbreaks are often caused by sewage contamination of drinking water or recreational water.
Noroviruses are able to survive relatively high levels of chlorine and varying temperatures. They can survive on practically any surface, including door handles, sinks, railings and glassware. On hard surfaces, they have been found to survive for up to 12 hours. On contaminated carpet, noroviruses have been found to survive for up to 12 days.
What are the symptoms and treatment?
People infected with norovirus usually develop symptoms of gastroenteritis within 24 to 48 hours, but symptoms can start as early as 12 hours after exposure. The illness often begins suddenly.
The main symptoms of norovirus illness are:
- vomiting (children usually experience more vomiting than adults)
- stomach cramps
Other symptoms may include:
- low-grade fever
- muscle aches
- fatigue (a general sense of tiredness)
About 300 to 400 outbreaks of norovirus are reported to the Public Health Agency of Canada every year. Many outbreaks in the community go unreported. Only the common cold occurs more often.
Most people feel better within one or two days, with symptoms resolving on their own and no long-term health effects. However, pregnant women, people with compromised immune systems, young children and the elderly are at risk for developing more serious complications, like dehydration.
As with any disease causing diarrhea or vomiting, people infected should drink plenty of liquids to replace lost body fluids and prevent dehydration. In severe cases, patients may need to be hospitalized and given fluids intravenously.
There is no vaccine or medicine that will prevent a norovirus infection, and norovirus cannot be treated with antibiotics because antibiotics fight bacteria, not viruses. Also, even after having the illness, you can still become re-infected by norovirus.
How do I avoid getting sick?
These tips will help protect you and your family from noroviruses:
- Wash your hands after using the washroom and changing diapers, and before preparing or eating food.
- Do not eat raw shellfish. Cook it thoroughly before eating it, especially clams and oysters.
- Wash raw fruits and vegetables thoroughly with clean, safe running water before you prepare and eat them. Use a brush to scrub produce with firm or rough surfaces, like oranges, cantaloupes, potatoes and carrots.
- Thoroughly clean contaminated surfaces, and disinfect using chlorine bleach, especially after an episode of illness.
- After vomiting or diarrhea, immediately remove and wash clothing or linens that may be contaminated with the virus (use hot water and soap).
- If you have been diagnosed with norovirus or any other gastrointestinal illness, do not prepare food or pour water for other people while you have symptoms, and for the first three days after you recover.
- Avoid contact with others until you are well again.
Also, these safe food practices will reduce your risk of contracting norovirus and other foodborne illnesses.
What does the Government do to protect me?
In Canada, several government organizations work together every day to keep your food safe:
- Health Canada makes food safety standards and policies to help minimize the risk of foodborne illnesses.
- The Canadian Food Inspection Agency (CFIA) enforces these policies and standards and carries out inspections to make sure the food industry meets its food safety responsibilities. The CFIA works with Health Canada to make sure that foodborne illness is detected early and warnings go out to the public quickly.
- The Public Health Agency of Canada studies the incidence and causes of diseases in Canada, conducts outbreak surveillance, and coordinates outbreak response.
The Government of Canada works very hard to protect your health and safety:
- We are carrying out a five-year Food and Consumer Safety Action Plan, to strengthen and modernize Canada's safety system and make sure you can have confidence in the quality and safety of the food, health and consumer products you buy.
- We are investing $75 million more in Canada's food safety system (on top of the $113 million committed in 2008) to hire more inspectors, update lab technology, and improve communication with Canadians.
- We support and participate in public awareness campaigns about safe food practices, like the Canadian Partnership for Consumer Food Safety Education's Be Food Safe program, which encourages Canadian consumers to think of food safety at every step of the food handling process, from shopping for groceries to re-heating leftovers.
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