The number of gastrointestinal illnesses linked to oysters has grown in British Columbia by 22 cases in the past two weeks, according to Canadian health officials. As of March 6, a total of 289 clinical cases of gastrointestinal illness linked to oysters have been reported in three provinces: British Columbia (201), Alberta (40), and Ontario (48). No deaths have been reported.
Individuals became sick between December 2016 and February 2017. All individuals who became ill reported having eaten oysters.
The source of illness has been identified as oysters from British Columbia but the cause of the contamination has not been identified. The outbreak is ongoing with illnesses linked to raw and undercooked oysters continuing to be reported, indicating contaminated oysters remain on the market (including restaurants, seafood markets and grocery stores).
Although not all cases of illness have been tested, testing of several cases has confirmed the presence of norovirus infection. It is suspected that norovirus illness, caused by consumption of contaminated oysters, is the cause of illness in the untested cases.
The outbreak is ongoing, indicating that contaminated oysters remain on the market (including restaurants and seafood markets and grocery stores).
Noroviruses are a group of viruses that can cause gastroenteritis in people, an illness that usually includes diarrhea and/or vomiting. Noroviruses are found in the stool or vomit of infected people. They are very contagious and can spread easily from person to person. Some foods can be contaminated at their source. For example, shellfish like oysters may be contaminated by sewage in water before they are harvested.