Other virulence factors may be involved in causing illness but they have not been characterized as yet. However, this virulent strain has been known in Asia since 1994 and has been increasingly isolated from cases of diarrhea in Japan, India, and other countries. This raises the possibility that this strain was introduced to U.S. coastal waters by ballast water discharged from ships which had traveled to Asia. A similar situation apparently occurred 4 years ago when V. cholerae was detected in oysters in Mobile Bay, Alabama. Prevention of foodborne illness Fortunately, most Americans prefer to eat their seafood cooked baked, fried, or boiled and this heat treatment effectively kills foodborne pathogens present in raw fish and shellfish.
Vibrios are heat sensitive and destroyed by adequate cooking.
Nevertheless, even adequate cooking cannot prevent foodborne illness if cooked shellfish are subsequently recontaminated. This scenario occurred in Louisiana in 1978 when cooked shrimp were returned to boxes in which raw shrimp had been shipped and then were held at warm temperatures for several hours before serving. Precautions should also be taken to prevent an increase in numbers of vibrios between harvest and consumption. Such inadequately cooked fish and shellfish have caused a variety of foodborne disease outbreaks due to parasitic worms, viruses, and bacteria. Since raw oysters are a significant source of a potentially lethal infection and to persons with liver disease, there are regulations in California, Florida, and Louisiana for posting warnings in places that sell raw oysters.