A dangerous flesh-eating bacteria is gaining a larger foothold in the US as the oceans warm

Dianne Manson/Getty Images

• The Vibrio vulnificus bacteria thrives in warm salty or brackish water. It can cause a flesh-eating disease that can sometimes result in amputations or death.
• In the southeastern US, people can contract a Vibrio infection after wading in this water with an open wound or eating raw shellfish from the water.
• A new case report has confirmed that this flesh-eating bacteria is spreading beyond its traditional region, in part due to warming ocean temperatures caused by climate change.
• Warning: This post contains graphic images.
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In the Chesapeake Bay and along the Gulf Coast, people can contract a dangerous flesh-eating bacterial infection after eating or handling raw shellfish.

Infections caused by Vibrio vulnificus can result in tissue death, and sometimes lead to limb amputations. Fortunately they're also rare in the US.

But a case report published today in the journal Annals of Internal Medicine suggests that rising ocean temperatures may lead the bacteria to spread to previously unaffected waters.

"In 2017, we saw three cases of severe skin infections, which raised some flags," Dr. Katherine Doktor, an infectious disease specialist at Cooper University Hospital who co-wrote the report, told Business Insider. "In 2018, we saw two more. These five cases are significant because in the eight years prior to 2017, we only saw one case of Vibrio vulnificus at our institution."

Read More: A man had his arm amputated after eating raw seafood contaminated with a potentially flesh-eating bacteria

People can catch the bacteria by handling or consuming raw shellfish

In the past, V. vulnificus infections have arisen after people swam in or came into contact with seafood from the Chesapeake Bay. But it was very rare for this to occur farther north, in the cooler Delaware Bay. That's no longer the case, according to Doktor and her colleagues. All five patients in the case report were infected after they were exposed to water in the Delaware Bay or consumed crabs in the area.

There are multiple species of Vibrio bacteria, and most make us sick, causing diarrhea, cramping, nausea, vomiting, and fever. Usually such symptoms pass in about three days, according to the Centers for Disease Control and Prevention (CDC).

But V. vulnificus can cause serious bloodstream infections that are accompanied by blood-filled blisters and necrotizing fasciitis, or flesh-eating disease, which kills body tissue. Often these infections can be treated with antibiotics, but the dead tissue must sometimes be removed, or the associated limb amputated, to keep the infection from spreading to other parts of the body. The bloodstream infection leads to death in 20% of cases.

People can get infected with Vibrio vulnificus by eating raw or undercooked shellfish, especially oysters, according to the CDC. It can also infect the skin if an open wound is exposed to brackish water or saltwater. Some people get infections after wading through storm flood waters. There were several Vibrio-associated deaths after Hurricane Katrina, for example.

"The infection courses through the entire body, kind of like a hurricane or tornado that ravages everything," Doktor said.

Of the five patients mentioned in the new case report, three had to get infected tissue removed, one man had his hands and feet amputated, and one person died in the hospital.

The New England Journal of Medicine, 2018.

A Vibrio vulnificus infection caused swollen blisters on a man's hand. The limb later had to be amputated.

The bacteria is expanding its range due to warming waters

Ian Waldie/Getty Images

An oyster farmer opens a diseased oyster in Sydney, Australia, in 2005.

Vibrio infections have also been reported in Europe, and in 2018, a South Korean man had to have his left forearm amputated after contracting the infection from eating raw seafood.

V. vulnificus isn't the only infectious disease spreading due to warming

Doktor said patients who contract severe Vibrio infections - like those in the case report - typically have other risk factors like liver disease, diabetes, or hepatitis.

"People who don't have any health problems who are exposed to bacteria may feel a little sick," she said, though she added that it's still a good idea to avoid consuming raw or undercooked shellfish.

But Doktor added that experts who study infectious diseases aren't just worried about V. vulnificus spreading due to warming.

"We're concerned about infections that were once considered only tropical could now occur at warmer latitudes," she said.

A study published in March forecasted that climate change is likely affect the range and distribution of mosquitoes carrying the Zika virus and dengue fever. According to that study, nearly 500 million new people could be at risk of exposure to these diseases by 2050.

USDA

The mosquito (Aedes aegypti) can spread several diseases as it travels from person to person.

If greenhouse-gas emissions continue to rise unabated, nearly 1 billion new people will be exposed to these disease-carrying mosquito species by the year 2080.