Between 2014 and 2018, investigators traced around 48 outbreaks of foodborne illness in California back to seafood.
Statistically, that’s not bad. California had 607 total foodborne illness outbreaks in 2014–2018, meaning only about 8 percent of all outbreaks were tied to seafood.
But there’s a story behind every number. Those 48 outbreaks caused 619 people to get sick, 21 of whom had to be hospitalized. Thankfully, no one died.
Most of the contaminated seafood items were served in fast food or sit-down restaurants, although others were eaten at home. The most serious outbreak occurred in March 2018, when approximately 100 people came down with norovirus after eating raw or undercooked oysters.
Investigators traced the mollusks to two oyster farms in Canada. The British Columbia Centre for Disease Control determined the oysters most likely became contaminated through human sewage in the water.
Special considerations for seafood safety
Fish and shellfish are an important part of a healthy diet. According to the Dietary Guidelines for Americans, you should eat seafood twice a week.
But, as with every other type of food, seafood can make you sick if it’s been improperly handled.
Foodborne illness outbreaks traced to seafood in California between 2014–2018
When researching the number of outbreaks traced to seafood in California, we made every effort to think of and include all the relevant foods possible. The 48 outbreaks mentioned above involved six different types of seafood. Some outbreaks were connected to more than one type of seafood:
- Oysters (22 outbreaks)
- Fish (21 outbreaks)
- Sushi (10 outbreaks)
- Shrimp (3 outbreaks)
- Crab (1 outbreak)
- Clams (1 outbreak)
It’s not surprising that oysters were the number one cause of seafood-related food poisoning. If you search for information about seafood safety on the web, oysters tend to get singled out. They have their own section in the CDC’s article “Foods That Can Cause Food Poisoning.” They also have their own page on the FDA’s website: “Raw Oyster Myths.”
One reason oysters get special attention is that they can carry multiple different germs. The oysters from British Columbia that sickened 100 people in 2018 were contaminated with norovirus. But that’s not the only germ that raw oysters can carry. Vibrio vulnificus bacteria can be far more dangerous.
According to the CDC, the safest way to eat oysters is fully cooked. Avoid eating oysters raw or undercooked, especially if you have liver disease, diabetes, or a weakened immune system.
Seafood-caused illnesses associated with fish
Fish was the second most common cause of food poisoning in the data we collected from the CDC National Outbreak Reporting System. Of course, there are many different kinds of fish. The specific varieties involved in those 21 fish-caused outbreaks were:
- Tuna (11 outbreaks)
- Mackerel (2 outbreaks)
- Salmon (2 outbreaks)
- Wahoo (1 outbreak)
- Mahi Mahi (1 outbreak)
- Red Snapper (1 outbreak)
- Escolar (1 outbreak)
- Fish taco — the exact type of fish wasn’t identified (1 outbreak)
- Other — the exact type of fish wasn’t identified (1 outbreak)
As you can see, tuna accounted for more than half of the total outbreaks involving fish. In the California outbreaks, the specific germs found in the tuna were scombrotoxin and Salmonella enterica.
According to the FDA, tuna is one of the most common types of fish to carry scombrotoxin. And Salmonella is one of the 5 most common germs that cause food poisoning in the United States.
Tips for preparing seafood safely
Before you get too worried about the potential risks of eating seafood, remember it was linked to only 8 percent of outbreaks over a five-year period in California. If you know how to handle seafood properly, it’s unlikely to make you sick.
Preventing food poisoning from seafood boils down to three basic things:
- When purchasing seafood, choose it wisely
- Store seafood apart from other foods and at a safe temperature
- Thaw, cook, and serve seafood according to FDA guidelines
Buying fresh and frozen seafood
Whether you’re buying seafood fresh or frozen, the first thing you should check is that it’s being held at a safe temperature. Fresh seafood should be displayed in a refrigerated case or on a thick bed of ice.
For whole fish, also check for
- Clear and shiny eyes
- Firm flesh that springs back when pressed
- Red gills
Fish fillets should also have firm flesh, as well as red blood lines. Don’t choose any fillets that look discolored, dark, or dry around the edges.
For shrimps, scallops, and lobsters, look for clear flesh with a pearl-like color.
If you’re buying live shellfish, make sure their tags or labels include the processor’s certification number. This indicates they were harvested according to federal guidelines.
Live clams, oysters, and mussels should close when you tap them. Don’t buy any with cracked or broken shells.
Live crabs and lobsters should move their legs.
Frozen seafood should be frozen solid, with no ice crystals or other signs of thawing in the packaging. The packaging also shouldn’t appear damaged.
Storing seafood properly
Refrigerate or freeze your seafood as soon as possible after you buy it or receive it in a delivery. Keep it at 40°F or lower to keep germs from growing to dangerous levels.
Keep raw seafood separate from other foods, especially ones that don’t require cooking. This will help prevent it from cross-contaminating other items in your fridge or freezer. Also, don’t store sushi-grade fish with other raw fish or meat.
Thawing, cooking, and serving
The safest and easiest way to thaw raw seafood is in the refrigerator. In general, this method takes about 24 hours per five pounds of food.
If you’re in a hurry, you can thaw the food in cold water or in the microwave.
The cold water method typically takes 20–30 minutes per pound of food. To use it, seal the seafood in a plastic bag and submerge it in cold water. Keep the water temperature at or below 70°F and change the water every 30 minutes as needed.
If you’re planning to cook the seafood immediately after thawing, you can use the microwave. This is by far the quickest way to thaw food — it only requires about 7–8 minutes per pound.
Once your seafood is fully thawed, you’re ready to cook! The FDA recommends cooking raw seafood to 145°F. Cooking your food to this temperature will help kill germs and prevent foodborne illness.
Different types of seafood react differently when cooked. When fish reaches the proper temperature, it becomes clear and is easily separated with a fork. Shrimp, scallops, crab, and lobster flesh turns clear and firm. As for clams, mussels, and oysters, their shells should open during cooking. Throw away any shells that don’t open.
Make sure you put cooked seafood in the fridge within two hours of cooking. Only leave it out longer than two hours if you have holding equipment to keep it warm (135°F or higher).
As a rule of thumb, eat leftover food within seven days of when it was first thawed, opened, or prepared.
Is sushi safe to eat?
We’ve established that raw seafood can carry illness-causing germs. So what about sushi? Is it safe to eat?
It depends. Sushi is generally safe, but it’s more likely to make you sick than fully cooked seafood. If you or someone you’re serving is pregnant, younger than 5, age 65 or older, or has a weakened immune system, it’s a good idea to stay away from sushi.
If you work for a food establishment that serves sushi, you must publish a consumer advisory to make guests aware of the increased risk of foodborne illness.
Follow the policies set by your local health department to prepare sushi safely. Those policies likely include purchasing sushi ingredients from approved suppliers and storing them at proper temperatures.
During preparation, take care not to cross-contaminate other food items. For raw sushi, only use sushi-grade fish that was previously frozen. The freezing process helps kill parasites that might have been in the fish.
Learn more about food safety
For more food safety tips, check out our California food handlers card training. Or, if you usually cook only for yourself and your family, try our Food Safety in Home Kitchens course.
— Jessica Pettit
