Oysters are filter feeding animals that can concentrate Vibrio bacteria from the water into their system. This concern exists for any raw oysters regardless of harvest from approved or questionable waters. When eating shellfish, particularly oysters, be sure that they are properly and thoroughly cooked. Thorough cooking kills the Vibrio bacteria and markedly reduces the risk of becoming ill. Steaming to open the oyster shells or blanching the shellfish does not always provide enough heat to kill all the Vibrio bacteria.
Additional heating is necessary to impart a noticeable cooked appearance.
Avoid cross-contamination of previously cooked shellfish with raw shellfish. A common cause of cross-contamination is storing cooked shellfish in the original container used for raw shellfish, or storing raw and cooked shellfish in the same area. Most healthy individuals are not troubled by Vibrio vulnificus infections from water or food. Also, extensive federal and state regulatory programs monitor the production and marketing of raw shellfish to assure product safety. Thus, the Vibrio vulnificus problem is primarily restricted to individuals in the risk categories.