The U.S. Food and Drug Administration has announced several recalls for oysters and clams that might be tainted with norovirus, a serious illness that affects the stomach.

The contaminated oysters were sourced from British Columbia, Canada, with the first recall occurring in California.

“Consumers should refrain from consuming these potentially contaminated oysters. If you experience symptoms, please contact your healthcare provider,” the FDA advised in a press release.

Additionally, another recall by the FDA covers oysters from Washington State as well as Manila clams, both of which may also carry norovirus.

Here’s what we know regarding this ongoing recall.

Canadian Oysters

A recall issued on December 13 by S&M Shellfish Co., located in San Francisco, identified affected products sold under the names Fanny Bay, Buckley Bay, and Royal Miyagi Oysters.

These oysters were reportedly harvested in British Columbia between December 1 and December 9 by Pacific Northwest Shellfish and Union Bay Seafood.

The FDA has also broadened the recall, which now includes oysters sold to restaurants and grocery stores across Arizona, California, Colorado, the District of Columbia, Florida, Georgia, Hawaii, Illinois, Kentucky, Missouri, Nevada, New Jersey, New York, North Carolina, and Pennsylvania.

Washington State Oysters and Manila Clams

Likewise, on December 12, a recall for oysters and clams shipped in Washington state and California was issued. The FDA has since expanded this initial recall to include eateries and food retailers in Arizona, California, Florida, Massachusetts, Michigan, and New York.

The FDA indicated that the oysters and clams recalled from Washington state were harvested by Rudy’s Shellfish from November 15 to December 11.

“The FDA is currently gathering more information regarding the distribution of these oysters and Manila clams and will continue to supervise the investigation, providing support to state authorities as necessary,” stated the FDA.

Symptoms of Norovirus

The FDA mentions that food contaminated with norovirus might appear perfectly normal in smell, taste, and appearance. Symptoms can include diarrhea, stomach cramps, nausea, vomiting, or fever after consuming affected oysters.