Raw oysters from British Columbia, Canada, have sickened more than 100 people in California and has been linked to a norovirus outbreak. The Food and Drug Administration (FDA) issued a warning Wednesday urging people not to consume raw oysters.

As of April 27, about 100 people reported of sickness after consuming oysters sold at restaurants and by retailers in California. The FDA warned the latest outbreak was linked to oysters harvested in the south and central parts of Baynes Sound, British Columbia, and distributed to Illinois, Massachusetts, and Washington.

In Canada, a total of 172 illnesses were reported linked to oyster consumption. However, no deaths were reported in the outbreak. 

“Avoid eating raw and undercooked shellfish, including oysters, to reduce your risk of illness,” California Department of Public Health's officer Dr. Karen Smith said in a statement. “If you do eat shellfish, cook it until it reaches an internal temperature of at least 145°F. Quick steaming isn’t sufficient to kill norovirus.”

What is norovirus and its symptoms?

Norovirus, which is a very contagious form of virus, can cause gastroenteritis, or stomach and intestinal illness. It spreads easily through food and drink, and symptoms can be seen 12 to 48 hours after the infection. Children younger than five, older adults, and those people with weak immune systems are more likely to have severe symptoms. However, some persons with norovirus infection may show no signs or symptoms.

Typical symptoms include nausea, vomiting (more often in children), watery diarrhea (more often in adults), stomach cramps, fever, chills, headaches, muscle aches and fatigue. 

According to the Centers for Disease Control and Prevention (CDC), norovirus causes nearly 19-21 million cases of acute gastroenteritis (inflammation of the stomach or intestines or both) each year in the United States. It also contributed to about 56,000–71,000 hospitalizations and 570-800 deaths, mostly among young children and the elderly.

Prevention from latest outbreak

The FDA has advised retailers not to serve raw oysters harvested from locations (or landfiles) within Baynes Sound: #1402060, #1411206, #1400483, and #278757. Consumers were also urged not to eat any raw oysters from these locations. 

CDC has recommended cooking oysters and other shellfish thoroughly (to 145°F or higher) before eating. Health officials also said contaminated oysters or shellfish may look, smell, and taste normal but can cause norovirus. 

The FDA and CDC recommend doctor's consultation if any person, who consumed raw oysters, suffer from diarrhea for more than three days, or it is accompanied by high fever, blood in the stool, or vomiting.