U.S. health authorities have issued a warning about the consumption of oysters and clams that may be contaminated with a highly contagious virus.

The Food and Drug Administration (FDA) alerted consumers not to eat these products and instructed restaurants not to serve them due to potential contamination with norovirus, a virus that causes gastrointestinal infections.

According to the agency, a preventive market recall was issued on Monday for seafood harvested in Washington state. The oysters and clams were collected between February 13 and March 3 by Drayton Harbor Oyster Company and the Lummi Indian Business Council.

The products were subsequently distributed to suppliers in several states, including California, Arizona, Florida, Georgia, Illinois, Nevada, New York, Oregon, and Washington.

Norovirus, commonly known as “stomach flu” though unrelated to influenza, can cause abdominal pain, vomiting, diarrhea, and, in severe cases, dehydration. Symptoms typically appear 12 to 48 hours after exposure, and most people recover within one to three days.

The FDA warned that contaminated food may look, smell, and taste normal, making it difficult to detect the risk. Authorities recommend that anyone who has consumed these products and experiences symptoms contact their healthcare provider and report the case to their local health department.

Restaurants that purchased these oysters or clams were instructed to discard them immediately. Employees were also advised to frequently wash hands and disinfect surfaces to prevent cross-contamination of other foods.

The FDA has not specified how many products may be contaminated and stated that the investigation is ongoing while supporting state authorities.

Individuals who believe they may have been exposed to norovirus after consuming the affected shellfish can report the case through the FDA’s Human Food Program.