Since January, Public Health — Seattle & King County has reported at least 39 people with illness suggestive of norovirus (nausea, vomiting and diarrhea) after eating raw oysters at one of several restaurants or private events in King County (see below).
The oysters served at each of the meals in the table below 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 3/17/17 for all species.
On site investigations were conducted by inspectors at each retail location where the oysters were purchased or consumed. No factors that can contribute to the spread of norovirus were found at any of the establishments, except for RN74 where a food worker was observed handling lettuce with their bare hands. Importantly, no ill food workers were found at any of the food establishments. Lacking any identified ill food workers, Public Health believes the most likely cause of the reported illnesses to be from consumption of raw oysters.
According to Dr. Meagan Kay, Medical Epidemiologist with Public Health, shellfish such as oysters, clams, and mussels are filter feeders. They ingest norovirus if it is present in the water. Because they are filter feeders, these shellfish may concentrate the virus to much higher levels than might be found in the surrounding water. Though all shellfish can be a source of norovirus infection if consumed raw or undercooked, oysters are much more commonly consumed raw than other shellfish; we are not aware of any norovirus cases linked to consumption of other types of shellfish right now.
When eating out, pay attention to any consumer advisories on the menu. The advisory is there to let you know which animal foods are served raw or undercooked. There is an increased risk of becoming ill from consuming any raw or undercooked meat or seafood.
Norovirus is a highly contagious viral illness that often goes by other names, such as viral gastroenteritis, stomach flu, and food poisoning.
The symptoms include nausea,vomiting, diarrhea, and some stomach cramping. Sometimes people additionally have a low-grade fever,chills,headache, muscle aches, and a general sense of tiredness. The illness often begins suddenly, and the infected person may feel very sick. In most people, the illness is self-limiting with symptoms lasting for about 1 or 2 days.
In general, children experience more vomiting than adults do.
Norovirus is spread person to person particularly in crowded, closed places. Norovirus is typically spread through contaminated food and water, touching surfaces or objects contaminated with norovirus and then putting your hand or fingers in your mouth and close contact with someone who is vomiting or has diarrhea.
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