You never know which bugs you’ll find in raw or undercooked shellfish.

   Vibrio vulnificus is the most dangerous and Norwalk virus is the most common. And unlike other pathogens, which target people with weakened immune systems, Vibrio parahaemolyticus can make just about anybody sick.

   “Parahaemolyticus is an equal-opportunity gut wrencher,” says George Hoskin of the FDA’s Office of Seafood.

   In June 1998, 416 people in 13 states were made ill by a strain of Vibrio parahaemolyticus.

   “This strain appears to be more virulent,” says Hoskin. Some speculate that it got to the Gulf of Mexico in ballast water dumped by a passing ship.

   Even if your seafood is thoroughly cooked, it could make you sick. Ciguatera toxin is a neurotoxin found in fish harvested from reef areas. Scombroid poisoning comes from histamine that can form on the flesh of fresh tuna, mahi mahi, and some other fish that aren’t kept cold enough (usually before they reach the store). Neither is killed by heat.
 

 Don’t eat raw shellfish, especially from the Gulf Coast.

 To cut your risk of ciguatera poisoning, avoid locally caught grouper, amberjack, and red snapper in tropical areas. It’s especially a problem in Florida, the Caribbean, and Hawaii. Avoid barracuda everywhere.

 The fish most likely to cause scombroid poisoning are fresh (not canned) tuna and mahi mahi.