No Fiction Needed: Vibrio Vulnificus Infections Scary Enough Already
Texas A&M University at Galveston Seafood Safety Lab scientist Mona Hochman '94 tackles the facts behind potentially deadly bacterium.
Mona Hochman '94 is the senior research associate for the Seafood Safety Lab, which tests 5,000 oysters a year for Vibrio parahaemolyticus and Vibrio vulnificus. Credit TAMUG Division of Marketing and Communications
When Vibrio vulnificus makes the news, Texas A&M University at Galveston (TAMUG) scientist Mona Hochman ’94 takes notice and often cringes at the way the dangerous bacterium is described.
“It’s typical for news reports to make this more fantastic than it actually is,” said the Seafood Safety Lab senior research associate who has spent 28 years looking for Vibrio bacteria where it shouldn’t exist in numbers concerning to humans.
“The thing about Vibrio vulnificus is that it’s fantastic enough on its own,” Hochman said. “We don’t have to make it scarier.”
How fantastically scary is Vibrio vulnificus? For anyone who is immunocompromised, infections from this bacterium can be caused by open-wound exposure to brackish water or eating undercooked shellfish/seafood.
Either type of infection could prove deadly within 48 to 72 hours if not treated, warned Hochman, a senior lecturer in Marine Biology and Honors Program chair for the College of Marine Sciences & Maritime Studies.
Florida has reported 21 cases of V. vulnificus infection this year, including four deaths and Louisiana, 15 cases with six deaths.
According to the U.S. Centers for Disease Control and Prevention, nearly one in five people with this infection die. Recent news reports also show scientists documenting Vibrio much farther north than the typical southern hotspots.
“I’m not a physician,” Hochman noted, while insisting anyone who begins feeling ill after eating raw oysters or notices pain, redness, or swelling around a wound after swimming in coastal waters should seek medical attention immediately. “People who are immunocompromised in any way should never have fresh raw oysters.”
As the overseer of an operation that fills a unique role in monitoring the efficacy of oyster processing nationwide, the Sea Aggie scientist should know. The Seafood Safety Lab tests 5,000 oysters a year for Vibrio parahaemolyticus and Vibrio vulnificus to ensure processed oysters are safe to eat.
Infection from Vibrio parahaemolyticus is more common than that of V. vulnificus, as it can affect anyone who consumes raw or undercooked shellfish with high bacteria levels. The infection causes severe gastroenteritis, or what Hochman describes as “an emergency evacuation of your system from all exits, no waiting.” It’s not deadly unless the patient gets severely dehydrated and doesn’t seek treatment.
When ingested, the rare systemic infection Vibrio vulnificus can cause spreads throughout the body and often feels like the flu at first. When it enters through an open wound such as a sore, cut, or insect bite, the infection can kill flesh and may require limb amputation to save a patient.
“We rarely find either Vibrio species in the processed oysters we test, because the post-harvest process is supposed to destroy them,” Hochman said of the Seafood Safety Lab. The post-harvest processes that are currently used by the oyster industry include individually quick-freezing, high hydrostatic pressure treatment, gamma-irradiation, or low-temperature pasteurization.
The safest way to enjoy raw oysters is to choose processed ones instead of fresh, the researcher added. “You can perform a post-harvest treatment and still serve it as a raw oyster. Calling it a raw oyster doesn’t mean it was freshly shucked. It simply means it hasn’t been cooked.”
But there’s more to the story. People often misunderstand risk levels, Vibrio’s origins, and what precautions to take; some mistakenly call it a virus when it is a bacterium, Hochman said.
“I don’t want to make light of Vibrio vulnificus; it’s scary enough on its own, but I would like the correct information to be out there,” Hochman said.
The Sea Aggie sifts through other facts and fictions about Vibrio vulnificus below.
FACT VS. FICTION
FICTION: Vibrio vulnificus eats flesh.
FACT: News stories about Vibrio vulnificus often describe the bacteria as “flesh-eating,” but that commonly used nickname or description doesn’t accurately describe what the bacterium is doing when it enters through a cut or sore. It doesn’t consume tissue. Instead, it causes necrotizing fasciitis, meaning it kills tissue by producing toxins and cutting off blood supply as the bacterium reproduces. The infected tissue can turn black and fall off.
FICTION: Vibrio vulnificus is deadly to anyone.
FACT: According to the Centers for Disease Control and Prevention, healthy people rarely develop severe illness.
“People whose bodies can’t fight off a systemic infection, those are the ones for whom it is deadly,” Hochman said.
High-risk groups include those with liver disease, diabetes, blood disorders, and immunocompromising conditions, such as those undergoing chemotherapy.
“Some people don’t understand what immunocompromised means,” Hochman said, noting it also includes those who’ve had gastric bypass surgery or gotten a gastric sleeve because they have less stomach acid to help prevent a serious infection.
FICTION: People can encounter Vibrio vulnificus anywhere in the Gulf or ocean if the water is warm enough.
FACT: Most seawater, including in the Gulf, is too salty for Vibrio. The bacterium’s upper salinity limit is around 25 parts per thousand, while Gulf salinity generally exceeds 32 parts per thousand. Instead, people get Vibrio in the low-to-moderate salinity estuaries or bays.
“If the bacteria got washed out of the bay, and the nearshore waters all of a sudden were more fresh than normal, Vibrio could be there too,” Hochman said. “So, I wouldn’t say you’d never catch it on the Gulf side, but it doesn’t tend to be in the ocean.”
FICTION: Pollution plays a role in how much Vibrio is in the water.
FACT: Vibrio bacteria are naturally occurring and so appear in all water with the right temperature and salinity levels. Storm runoff could affect salinity levels, but the bacteria pollution brings is not Vibrio.
“Vibrio’s been here longer than oysters have been here,” Hochman said. “It’s been here longer than people have been here.”
FICTION: Beachgoers should check monitoring services like Texas Beach Watch for Vibrio levels.
FACT: No one regularly monitors naturally occurring Vibrio. Texas Beach Watch checks for Enterococcus, which comes from fecal waste and is carried in stormwater runoff and sewage. The agency tests weekly during peak beach season and bi-weekly the rest of the year.
“They are talking about poop in the water,” Hochman explained.
Enterococcus can cause vomiting, diarrhea, and dehydration – and Beach Watch advisories should certainly be heeded – but note that those advisories have nothing to do with Vibrio bacteria.
