It's how norovirus works, and sometimes hepatitis too: https://www.livescience.com/62485-how-does-norovirus-get-into-oysters.html https://www.livescience.com/6

It's how norovirus works, and sometimes hepatitis too: https://www.livescience.com/62485-how-does-norovirus-get-into-oysters.html https://www.livescience.com/62485-how-does-norovirus-get-int... Some harvesters will hold oysters in sterile water for a few days to clean them out (Depuration). This usually works but it is hard to know for sure if the one on your plate got this treatment or not.