Pretty much any time of the year on the American Gulf Coast, oysters are plentiful on restaurant dining tables. The Gulf-grown bivalves are a staple crop for the region’s fishing industry and a beloved component of seafood feasts, served raw on the half-shell or broiled with bacon and breadcrumbs into oysters Rockefeller.
Now, though, concerns around Gulf oysters are growing following a major outbreak of Vibrio vulnificus, sometimes described as “flesh-eating bacteria,” in the state of Louisiana. Starting in June, cases of Vibrio vulnificus infection began popping up across Louisiana, sickening more than two dozen people and leaving five dead. Vibrio infections become more common during the summer months, as warmer waters provide a more suitable breeding ground for the bacteria. According to the Louisiana Department of Health, that’s a significant increase over previous years—across the last decade, the agency has typically only seen about ten cases of vibrio infection each year.
For those who are unfamiliar with Vibrio, it’s a genus of bacteria with more than 100 different variants, some of which can cause a severe disease called vibriosis in humans. According to the Centers for Disease Control and Prevention (CDC), Vibrio vulnificus is among the most dangerous of these variants, and as many as 1 in 5 people who are infected with the bacteria die. Others may require limb amputation or extended hospitalization.
Vibrio has long been a concern for oyster enthusiasts, but those concerns have grown in recent years thanks to warming waters caused by climate change. In the last 30 years, Vibrio vulnificus infections have increased “eightfold,” and as water temperatures continue to rise, those infections will only become more common.
Does that mean that you should stop eating Gulf oysters, though? As it turns out, the answer is a little more complicated than you might think.
According to the Louisiana Department of Health, 85% of this year’s Vibrio vulnificus cases weren’t from eating oyster but from exposure to brackish or coastal waters, like walking into the Gulf with an open wound. “It just happens,” says Dr. Keith Schneider, a professor of food safety at the University of Florida’s Institute of Food and Agricultural Sciences. “Somebody steps on an oyster shell, or goes swimming with a cut in an estuary where the Vibrio vulnificus bacteria is present.” As for the deaths, a Louisiana Department of Health spokesperson declined to tell Serious Eats whether any had been linked to oyster consumption, citing patient confidentiality.
Eating oysters does still pose a risk of ingesting the Vibrio vulnificus bacteria, though, but Schneider says there are several ways that consumers can mitigate that risk. His first recommendation is to follow a 4,000-year-old piece of advice that still holds today: Stick to eating raw Gulf oysters in months with the letter “R” in them. “Sometimes, the old adage is just true,” Schneider says. “Warmer waters mean that there are more pathogens in the water, and we have seen upticks in [Vibrio] illnesses in the summer for decades. These organisms just thrive in warmer water.”
Once the oysters have been pulled out of the water, how they’re handled is incredibly important, which means that it’s a good idea to get your raw Gulf oysters from reputable purveyors—and from restaurants that handle and serve them with care. Schneider suggests staying away from the super-cheap raw oyster happy hour deals, where a focus on low prices and volume could result in improper handling.
“You want to make sure that they’re serving you oysters that are still alive and healthy, because if they’re not, that bacteria will start to multiply,” he says. “That’s important, because you can’t tell by look or smell if an oyster is harmful.”
Some people, though, may want to skip raw oysters altogether. Individuals who have liver conditions like hepatitis are much more vulnerable to Vibrio vulnificans infection from consuming raw oysters than those who do not have those conditions, and the complications can be life-threatening. Experts suggest that very young children, the elderly, immunocompromised, and pregnant people should probably skip raw oysters in general, because their immune systems are less able to fight off an infection caused by the bacteria.
Even though he knows more about Vibrio than most people, Schneider still enjoys eating Gulf oysters. “My own personal risk calculus really depends on the time of the year and the number of oysters I’m planning to consume,” he says. “I don’t have any liver conditions, but I am getting on up there in age, so maybe at some point I will stop. But I think generally the risk is fairly low, especially if you’re getting them from a reputable establishment.”
In terms of keeping the Gulf’s oyster population as healthy as possible, there are a number of systems in place to monitor the waters in which they’re caught, as well as the oysters themselves. Agencies like Louisiana’s Molluscan Shellfish Program monitor the production of oysters and require producers to use shipping tags that can be used to track specific bags of the bivalves in the event of an outbreak. “The health agencies react quickly to these outbreaks,” Schneider says. “If there’s an outbreak, they’re going to be able to find that exact batch of oysters and pull it off the shelf.”
Oyster producers are also experimenting with new-to-the-industry technologies to reduce Vibrio infections in raw oysters. At Prestige Oysters in Dickinson, Texas, a method called high-pressure processing (HPP) is used to simultaneously separate the oyster meat from its shell and virtually eliminate foodborne pathogens like Vibrio bacteria, while extending the shelf life of the oyster. The result is a raw but safe oyster that is ready to slurp, with a lower risk of illness. The downside: Many consumers don’t like the way that the HPP process changes the texture and fresh flavor of the raw oyster, even if it is less likely to make them sick.
If you really want to be as safe as possible, there’s a straightforward solution: Just eat cooked oysters. Heat kills Vibrio bacteria, and just a few minutes of cooking can all but eliminate your risk of getting sick. The CDC recommends boiling or frying oysters in hot oil for three minutes, or roasting them in the oven at 450°F for 10 minutes to ensure that all bacteria have been killed by the heat. You should, however, ignore the urban legends that hot sauce, lemon juice, or alcohol will kill the bacteria—none of these “remedies” are supported by research.
