The Public Health Agency of Canada is investigating an outbreak of gastrointestinal illnesses linked to raw and undercooked oysters. The illnesses have occurred in British Columbia, Alberta, and Ontario. Testing of several cases, but not all, has confirmed norovirus. Officials think that norovirus is the cause of illness in the untested cases.
The outbreak notice states “the risk to Canadians is low.” This type of illness can be avoided if oysters are cooked to an internal temperature of 90°C/194°F for a minimum of 90 seconds, and proper hand washing and food safety practices are followed.
As of February 7, 2017, 202 clinical cases of illness linked to oysters have been reported in three provinces. The case count per province is: British Columbia (143), Alberta (35), and Ontario (24). Individuals got sick between December 2016 and January 2017. All ill persons reported having eaten oysters. Shellfish such as oysters can be contamianted by sewage in the water before they are harvested. Because oysters are filter feeders, any bacteria or viruses they consume can be concentrated in their flesh.
The symptoms of norovirus are diarrhea, vomiting, nausea, stomach cramps, low grade fever, headache, chills, muscle aches, and fatigue. Most people get better on their own within a day or two. But some people can become seriously ill and need to be hospitalized after this type of infection, usually because of dehydration.
Norovirus is a very contagious virus and the illness is spread through contaminated food and water and person-to-person. To protect yourself against this virus, always fully cook seafood before eating it. Discard any oysters that do not open after cooking. Eat oysters right away after they are cooked and promptly refrigerate leftovers. To avoid cross-contamination, wash cutting boards, counters, knives, and other utensils after preparing raw foods.
Norovirus can survive relatively high levels of chlorine and varying temperatures, which means it can survive on contact surfaces. If someone in your home has norovirus, clean contaminated surfaces using chlorine bleach. If you are diagnosed with norovirus or any gastrointestinal illness, do not prepare food or pour drinks for others while you have symptoms, and for the first 48 hours after you recover. Check with your doctor about returning to work if you work in the health care or food service industries or in a school or daycare center.