Just How Risky Are Raw Oysters Anyway?

Nov 14, 2018

A former North Dakota lawmaker recently died after eating at a New Orleans restaurant. The alleged culprit: a bacterial infection from a raw oyster. Oysters have long been a trademark of southern cuisine, but they also pose health risks for some. So, just how dangerous is it to eat raw oysters?

Thomas “Uptown T” Stewart is the famous oyster shucker at the Uptown New Orleans restaurant Pascal’s Manale. He’s worked at the restaurant for more than 30 years, and he knows his clients well. It seems like he’s always shouting “What’s happening, y’all?” to people walking through the front door.

Stewart’s side of the bar is covered by a pile of raw oysters and ice. One by one he digs them out of the ice. He pries open the shells with a knife and slices the meat free with effortless speed.

Brent and Paula Coussou are on the other side of the bar. They’re each nursing a beer and there’s a row of empty oysters between them. They say they’re regulars making the drive from Lafitte for as long as Stewart has been working there.

 

“This guy here's the best. The best,” says Brent Coussou.” I mean, I've been to a lot of places and it's just, his oysters are very clean. He doesn't have any chiplies in his oysters.”

I’m not sure if that’s an official term, or if he’s pulling my leg. But he’s referring to those crunchy bits of shell you sometimes slurp down with the raw oyster.

Coussou heard the news about the politician who died, but he’s not worried. He says he’s never gotten sick. But of course, sometimes, people do get sick. And every now and then, someone actually dies.

“There's always going to be a small amount of risk,” says Dr. Fred Lopez, who studies infectious disease at LSU’s Health Sciences Center.

Lopez says the biggest danger comes from a bacteria called Vibrio vulnificus. That’s what allegedly killed the politician from North Dakota. And it’s actually everywhere.

Vibrio vulnificus is a naturally occuring bacteria that thrives in brackish waters when the temperature is above 68 degrees Fahrenheit. As a result, it’s actually more common in the Gulf of Mexico where the waters are warmer -- compared to the East and West coasts.

"If you're consuming a raw oyster that comes from the Gulf Coast waters...particularly in the summer months,” says Lopez, “You have to assume that it has Vibrio vulnificus."

But, even though many oysters are exposed to Vibrio vulnificus, that doesn’t mean they’re dangerous to everyone. People with specific pre-existing health problems are most vulnerable.

That list includes liver disease, diabetes, kidney disease, alcoholism, cancer, and people being treated with chemotherapy for cancer, and a few others. Generally speaking, people with weakened immune systems. Lopez says those people shouldn’t eat raw oysters -- period.

“They can eat shellfish,” he says. “They just need to make sure that they're thoroughly cooked -- boiled, fried, steamed, etc.”

Proper cooking kills the bacteria completely. All things considered,Vibrio vulnificus infections are still very rare. If you don’t have one of those pre-existing health issues, Lopez says you’re probably fine. It’s nothing to worry about.

But in cases where people with weakened immune systems are infected by Vibrio vulnificus, anywhere from one-third to one-half of those people die.

“That's a very high mortality rate,” says Lopez.

That’s why there are very strict regulations around oyster harvesting. The Interstate Shellfish Sanitation Conference (ISSC) sets those regulations for the Food and Drug Administration.

“Probably, shellfish and milk are the two most regulated foods in the country,” says Ken Moore, Executive Director of the ISSC.

There’s an old adage, that you should only eat raw oysters in months with an “R.” September through April -- basically the cooler months. So this isn’t a new idea.

Moore says regulations have tightened over the last ten years or so. For example, during the warm summer months oysters that are meant to be eaten raw have to be refrigerated within an hour of harvesting. He says it’s had a positive effect.

“We've actually seen a reduction in [raw oyster Vibrio vulnificus] cases,” Moore says. “We think that the controls that we have in place are actually keeping those numbers low.”

Dr. Alex Billioux agrees. He’s the Assistant Secretary for Louisiana’s Office of Public Health.

“It is very, very rare to become ill from eating oysters,” says Billioux.

 

But, Billioux says even though infections from raw oysters are down, the amount of Vibrio vulnificus in the water is actually increasing due to warming waters.

Even though Vibrio vulnificus infections by eating raw oysters declining in the state and across the country, overall infections are climbing. Officials say that's because the oceans are warming.
Credit Louisiana Office of Public Health

“I definitely expect our jobs to become harder as the waters continue to warm because of climate change,” he says.

That could mean more testing, scrutiny, and risk in the future.

“I think that's sort of the big point when we start talking about the climate change effects. On not just the planet, but Louisiana,” Billioux says. “It really can touch everything.”

So, if you don’t have any vulnerable health issues -- slurp those raw oysters while you can. Or just toss ‘em in a deep fryer.

 

Support for the Coastal Desk comes from the Walton Family Foundation, the Greater New Orleans Foundation, the Foundation for Louisiana, and local listeners.

 

Clarification: A previous version of this story referred to Vibrio vulnificus by the shorthand "Vibrio" in several places. Though the Vibrio bacteria family includes Vibrio vulnificus, not all Vibrio members are dangerous to human health. The the shorthand references have been made more specific.