Cholera in Louisiana. Widening spectrum of seafood vehicles.

The largest cholera outbreak in the United States in over a century occurred in Louisiana from August through October 1986. Eighteen persons in 12 family clusters had stool culture or serologic evidence of infection with toxigenic Vibrio cholerae 0-group 1. Thirteen of these persons had severe diarrhea, and 4 required intensive care unit treatment. Although all 18 survived, 1 96-year-old woman with suspected cholera died shortly after hospital admission. A case-control study showed that case-patients were more likely than neighborhood control subjects to have eaten cooked crabs or cooked or raw shrimp during the week before illness. Case-patients who ate crabs were more likely than control subjects who ate crabs to have undercooked and mishandled the crabs after cooking. A third vehicle from the Gulf waters, raw oysters, caused V cholerae 01 infection in two persons residing in Florida and Georgia. All three seafood vehicles came from multiple sources. Stool isolates from the Louisiana case-patients were genetically identical to other North American strains isolated since 1973, but differ from African and Asian isolates. While crabs are the most important vehicle for V cholerae 01 infection in the United States, shrimp and oysters from the Gulf coast can also be vehicles of transmission. A persisting reservoir of V cholerae 01 along the Gulf coast may continue to cause sporadic cases and outbreaks of cholera in Gulf states and in states importing Gulf seafood.