Fishing for safe seafood.

Last May, a 38-year-old Los Angeles man with diabetes developed fever, chills, nausea, and muscle pain two days after eating raw oyster from Texas. Three days later, in a hospital intensive care unit, he died of blood poisoning.

A week later, 46-year-old Los Angeles man with cirrhosis of the liver came down with fever, sweats, and nausea one day after eating raw ousters from a different source in Texas. Despite antibiotics and hospital care, he, too, died within days.

And later that month, also in Los Angeles, a 51-yeat-old woman with hepatitis developed fever, nausea, and muscke aches a day after she ate raw oysters from Louisiana at a party. Two days later she was dead from blood poisoning.

Each day in the United States, hundreds - perhaps thousands - of people get sick from eating seafood. For most, it's an inconvenience, maybe an unpleasant day or two of diarrhea and stomach cramps. Others are disabled for weeks ... or even years. And a small number - mostly those who eat raw shellfish - die.

All the from one of the healthiest foods you can eat. Seafood is remarkably low in (heart-damaging) saturated fat. And it's the richest source of omega-3 fatty acids, which could protect against heart attacks.

The trick is to get the most benefit ... at the least risk.

Contaminated seafood causes about 113,000 cases of food poisoning each year in the U.S., according to the Food and Drug Administration (FDA). But that's clearly an underestimate. "There are probably many incidents that are not reported," says Sean Altekruse, an FDA epidemiologist who tracks seafood poisoning for the Centers for Disease Control (CDC) in Atlanta.

Unlike with meat, where ground beef is the chief culprit, the most popular varieties of seafood are among the safest. Canned tuna, for example, poses little or no risk of illness. The same goes for shrimp, cod, imitation crabmeat, breaded fish filletss and fish sticks, flounder and haddock, catfish, and salmon (canned or fresh). That takes care of more than two-thirds of the seafood that Americans buy. Some of the other third can be a bit dicier.

RAW SHELLFISH

"The biggest seafood hazard by far is raw or undercooked shellfish," says Morris Potter of the CDC. About 20 million Americans eat raw shellfish, says the FDA. And it's raw shellfish that accounts for more than 90 percent of seafood poisoning cases.

"One has to bear in mind that when you eat raw shellfish you're eating a whole living organism complete with its GI tract," Potter points out. "That would be equivalent to plucking a live chicken and eating it whole, guts and all."

What's more, shellfish feed by filtering two to three gallons of water an hour. That means they take in whatever's floating by - not only plankton and other food, but viruses, bacteria, mercury, and who-knows-what-else.

Here's what could be waiting for you in your next oyster, mussel, or clam:

*Norwlak Virus. The most common cause of shellfish poisoning comes from human sewage. It causes nausea, vomitting, or diarrhea, but most of the 100,000 or so people who are attacked each year recover within a day or two.

"In general, it's a mild illness," says Melvin Kohn of the Louisiana Department of Health and Hospitals, "People get very sick for a couple of days but they usually don't die."

As with just about all seafood contamination, you can't see or smell Norwalk. And stewing or steaming doesn't necessarily solve the problem.

"We know that high degrees of heat clearly can kill it and low degrees of heat don't," says Kohn. "But how many degrees it has to be has not been determined."

*Vibrio. The nastiest strain found in the U.S. is Vibrio vulnificus, which kills about 10 to 15 people each year. Vibrio bacteria thrive in the waters of the Gulf of Mexico, so seafood that comes out of that environment, particularly when the waters are warm, have Vibrio on them," notes Morris Potte

In fact, every case that the CDC has traced since 1990 came from raw shelifish harvested in the Gulf.

Only a small percentage of the population is susceptible to Vibrio vulnificus infections, but about half of those who get it die. "There aren't very many trivial Vibrio vulnificus infections," says Potter. The most vulnerable: people suffering from liver disease, liver damage caused by too much alcohol, or iron-overload disease (hemochromatosis), and people with diabetes, AIDS, or cancer.

Fortunately, heat destroys Vibrio. So as long as you avoid raw or undercooked Gulf Coast shellfish, especially from May through November, you're probably safe.

FINFISH 

While most seafood poisoning is caused by raw shellfish, fish with fins aren,t always squeaky clean. And cooking may not make a contaminated fish safer.

*Ciguatera. "It's the most common finfish food poisoning in the United States," says W. Robert Lange of the Johns Hopkins School of Medicine.

Some 8,000 Americans a year are made ill by the ciguatera toxin, which is produced by plankton that grow on tropical reefs. Small fish that eat the plankton also eat the toxin, and large predatory fish that eat the small fish end up carrying even more ciguatera. In the U.S., ciguatera poisoning cases are concentrated in Florida, Hawaii, Puerto Rico, the Virgin Islands, and Guam.

"The early symptoms can mimic any kind of foodborne iliness, typically nausea, abdominal cramps, and diarrhea," says Lange. "Later, a 'pins and needles' sensation occurs around and inside the mouth and in the hands and feet." Victims often experience temperature reversals," where hot things feel cold and, more likely, cold things feel hot.

While the effects of ciguatera usually last about two weeks, "as many as 20 percent of all victims will still have some symptoms at six months and five percent at two years," says Lange.

Because of ciguatera's neurological symptoms, doctors have been known to misdiagnose it as multiple sclerosis.

What can you do to avoid ciguatera? Don't eat barracuda, no matter where you are," warns Lange. If you're visiting the Bahamas or the Caribbean, pass up grouper, red snapper, or any fish dish like bouillabaisse where vou don't know the ingredients.

"In the States, if you want grouper or red snapper, stick to smaller, younger specimens, which haven't accumulated as much toxin."

*Scombroid Poisoning. It's less common and less serious than ciguatera. Scombroid poisoning occurs when certain fish aren't kept cool enough. Bacteria on the fish create large amounts of histamine, which can cause tingling and burning sensations around the mouth, as well as diarrhea, cramping, and an itching rash. Symptoms seldom last more than a few hours.

In the U.S., "most cases involve scombroid fish like mahi mahi or fresh tuna," says Lee Weddig of the National Fisheries Institute, a trade group.

CHEMICAL CONTAMINANTS

Harmful metals, industrial chemicals, and pesticides like mercury, PCBs, dioxin, and chlordane often wash into rivers, lakes, and oceans. In fact, 47 states currently have fish consumption advisories that warn about eating certain species. They cover 1,740 rivers and lakes (including all of the Great Lakes) and large chunks of coastal areas.

"At greatest risk of eating contaminated fish are sports fishermen, charterboat crews, and those who need to fish for food like some Native Americans, the poor, and recent immigrants to this country," says Tom Sinks of the CDC's Center for Environmental Health.

The most common reason for consumption advisories: mercury. In large amounts, the metal can cause brain and nerve damage, especially to fetuses and young children.

Large fish like fresh tuna and swordfish have the highest levels. But a new study from the Seychelles Islands off the coast of East Africa concluded that the amounts in those fish don't appear to cause problems.[1]

"The children of mothers who ate a lot of these fish during their pregnancies do not show any signs of harmful effects, at least up to the age of two and a half," says researcher Thomas Clarkson of the University of Rochester in New York. His team is continuing to monitor the children.

Still, says Sinks, while there may be little evidence that people get enough mercury or other contaminants from fish to suffer short-term harm, "there might be subtle, adverse neurological problems over the long term that we aren't noticing."

A recent study underscores his point. Researchers tested children of women who ate at least four pounds a year of PCB-contaminated Lake Michigan fish for six years before thev gave birth. Those children, now 11 years old, are more likely to have lower IQs and to lag behind their peers in reading comprehension.[2]

[1] Neuro Toxicology 16:711, 1995. [2] New England J. Medicine 335:783, 1996.

How to Buy Fresh Fish

Do you knowa freshfish when you see one? Roger Berkowitz does. He,s the CEO of Legal Sea Foods, a Massachusetts company that operates a processing plant, retail markets, and a chain of restaurants in the Northeast. Here,s Berkowitz,s advice:

"A fresh fish should have the nice clean smell of the ocean. If a whole fish, a fillet, or a steak smells repugnant or of ammonia, it's old or has been mishandied.

"If little particies of flesh come off when you run your hand across the fillet, the fiesh is breakin down and the fish is old. Wiggle the center bone of a fish steak. If the meat pulls away, it,s old. White-fleshed fish should have a bright, white color. If there are yellow tones, it,s old."

What's the best way to store seafood that you're going to cook within 48 hours? "Keep it cold as much as possible as long as possible until it's ready to cook. Bury it in ice."

Fish Fraud

Is that expensive red snapper at the fish counter really just cheaper rock-fish? Is that jar of pricey oysters weighed down by extra water? Do your fried clams have more breading than fish?

"Fish fraud goes on, but we don't know how often or how much," says Rich Cano, Chief of the Inspection Services Division of the National Marine Fisheries Service.

That's because seafood is not systematically checked for fraud.

What can you do to protect yourself? Shop at reputable stores and restaurants. And - assuming, tell a turbot from an orange roughy - "pick the freshest, cheapest fish available," advises Mary Snyder, who is in charge of fish fraud enforcement at the FDA.