There could be something extra lurking in shellfish folks have been eating in Seattle, and it’s not a tasty mignonette: Health officials say they’re investigating a possible norovirus outbreak after multiple reports of people falling ill after eating raw oysters.

As many as 39 people have become ill with symptoms suggestive of norovirus, Public Health – Seattle & King County says, including nausea, vomiting, and diarrhea.

Those who have fallen ill consumed raw oysters at one of several restaurants or private events in King County between Jan. 10 and March 20 (click here for the list).

Inspectors investigated each retail location where the oysters were purchased and consumed, and couldn’t find any factors that can contribute to the spread of norovirus at any of the establishments, except for one restaurant where a food worker was observed handling lettuce with their bare hands.

Public Health notes that no ill food workers were found at any of the food establishments. As such, the agency believes the most likely cause of the reported illnesses is from consuming raw oysters.

The oysters were harvested from different growing areas/bays in Washington State with the exception of four meals, accounting for 22 of the reported illnesses, which included oysters harvested from a small area in the Samish Bay growing area. A section of that growing area was closed on March 17, Public Health notes.

Shellfish including oysters, clams, and mussels are filter feeders, which means that if there’s norovirus present in the water they live in, they’re ingesting it. This can lead to norovirus concentrating in much higher levels than might be found in the surrounding water. All shellfish can be a source of norovirus infection if consumer raw or undercooked, Public Health notes, but oysters are eaten raw more often than other kinds of shellfish.

The agency recommends paying attention to any consumer advisories on the menu when eating out, which will let you know which foods are served raw or undercooked. There will always be an increased risk of getting sick from eating anything that’s raw or undercooked, so it’s basically up to you to take that chance.

“While most people recover after 1-3 days of these symptoms, the repeated bouts of throwing up can cause dehydration, particularly in children, older people, and people with underlying illnesses,” says Dr. Meagan Kay, Medical Epidemiologist with Public Health on the agency’s blog.

The agency has reported the illnesses to the Washington State Department of Health Shellfish Program which is responsible for tracking the reports and harvest locations of the oysters implicated in these illnesses.

Besides avoiding raw shellfish, here are some suggestions from Public Health on how to avoid infection:
• Wash hands, cutting boards, and counters used for shellfish preparation immediately after use to avoid cross contaminating other foods.
• Wash hands thoroughly with soap after using the bathroom or changing diapers, and before preparing any food or eating.
• Wait at least 48 hours after the last episode of vomiting and/or diarrhea before preparing any food for others.

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