North Carolina Sea Grant
Mariner's Menu

Mariner's Menu

October 21, 2013 | Joyce Taylor

seafood is safe to eat

Eating raw or partially cooked oysters, clams, mussels and scallops poses significant health risks for some people. Eating these raw or undercooked shellfish accounts for 85 percent of all seafood-borne illnesses. Shellfish need to reach an internal temperature of 145 F to be done. Just-opened shellfish are not fully cooked. A crinkled appearance to the meat typically indicates doneness.

The reason for the high incidence of illness from this handful of popular bivalves is simple. We eat them whole — digestive tract and all — and whatever microorganisms or toxins have accumulated in their guts reaches ours. As filter feeders, bivalve mollusks sit in one place and eat whatever the water brings them. If the water is contaminated by natural toxins, sewage or industrial pollution, so is the oyster, clam, mussel or scallop.

A naturally occurring bacterium, Vibrio vulnificus, poses a threat for people with certain medical conditions. Most infections occur from eating raw or partially cooked oysters. The bacterium can also enter the body through an open wound, cut, sore, puncture or burn on skin exposed to sea water or raw shellfish containing the bacteria. Vibrio vulnificus can be found in warm water along the coast, especially during the summer months. It does not pose any danger to most healthy people and can be killed by thorough cooking. Freezing does not destroy it. Nor does drinking alcohol or eating with hot pepper sauce.

Gastroenteritis usually occurs within 16 hours of ingesting the organism. Symptoms include chills, fever, nausea, vomiting, blood poisoning and even death within two days for people with weakened immune systems. More than 50 percent of infections from Vibrio vulnificus prove fatal for people with the health conditions listed here.

No major outbreaks of illness have been attributed to Vibrio vulnificus, but sporadic cases occur frequently.


People with any of the following medical problems are at risk and should not eat raw or partially cooked shellfish:

Older adults tend to be at increased risk because they suffer from these health conditions more often. Also, pregnant women, infants and very young children should eat fully cooked shellfish.

The best way to reduce the risk of illness is to keep within the seafood safety net. Never purchase shellfish from unknown or uncontrolled sources. They’re no bargain. Buy only from reputable dealers who buy from shellfish harvesters licensed under the National Shellfish Sanitation Program. If in doubt, ask to see the shipper’s tag that accompanies in-the-shell products. Also, ask to see the shipper’s number on shucked oyster containers. Such information tells who shipped the product and where it came from originally.

From: Mariner’s Menu: 30 Years of Fresh Seafood Ideas 

Contributed by Joyce Taylor

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