Rudy's Shellfish, based in the US city of Shelton, Washington, has recalled its oysters and Manila clams due to a norovirus outbreak, the Washington State Department of Health (WSDH) and the Interstate Shellfish Sanitation Conference (ISSC) have announced.

The recall includes oysters and Manila clams that were harvested between Nov. 15 and Dec. 11 from the Pickering Passage growing area, which is in the southern end of part of Puget Sound. Products have been distributed within Washington state and California, per a notice posted by ISSC.

Norovirus is a highly contagious foodborne illness that is often called "food poisoning" or the "stomach flu," reports the state health agency. Shellfish often become contaminated with the virus when untreated human sewage enters the marine environment. While any bivalve shellfish can be contaminated with norovirus, norovirus outbreaks are "more often linked to oysters because they are commonly eaten raw," WSDH advises.