As The Oceans Warm, A Flesh-Eating Bacterium Is Making Its Way North

If you were planning a beach vacation this year, you may have kept an eye out for great white sharks.

The apex predator made famous by Jaws (and, OK, The Meg and Sharknado) has been observed on East Coast beaches from South Carolina up through Cape Cod, causing potential beachgoers to be concerned after reports of close encounters and attacks.

Many marine biologists, however, are concerned about a much smaller, in fact microscopic, threat. They are tracking an unusual spike in Vibrio bacteria, which recently killed three people and sickened a fourth in Connecticut and New York, at least two of whom were swimming in Long Island Sound’s coastal waters.

Vibrio is a well-known summer nemesis for swimmers and fishermen in the Gulf of Mexico. It’s one of the reasons why the old adage goes that you shouldn’t eat oysters in months with no R in their name: Warmer water promotes bacterial growth, which oysters consume when they feed. Anyone who receives a cut while clearing up drenched debris after a cyclone is also at risk of infection from the bacterium. However, the appearance of Vibrio in the seas of the upper East Coast is a new and unknown hazard, exacerbated by climate change’s rapid ocean warming.

Researchers are concerned that Vibrio may become a permanent threat to people’s ability to enjoy the beach safely, and physicians who work in locations where it is already prevalent wonder if their northern colleagues will be aware of its possibly fatal consequences. “We are used to certain diseases in our area, but they are something that clinicians in the Northeast, for example, may not be as familiar with,” Cesar Arias, a professor and chief of infectious diseases at Houston Methodist Hospital, says. “All of these climate changes, including the tremendous warming of the oceans, are changing the geography of infectious diseases.”

Already, the Centers for Disease Control and Prevention estimates that Vibrio species cause 80,000 illnesses and 100 fatalities in the United States each year, with 52,000 of them caused by eating seafood. However, because shellfish safety is strictly enforced by federal agencies, the other type of Vibrio infection, caused by the species Vibrio vulnificus, is causing the most concern right now. These infections occur when bacteria-laden seawater penetrates a skin breach. An average year is thought to have 28,000 cases, however this is largely regarded an undercount.

These illnesses are treatable if people receive medicines as soon as possible. However, if not treated quickly, they can induce necrotizing fasciitis, a flesh-eating illness that can only be stopped by amputation, and can also put patients in septic shock in as little as two days. The germs can enter the body through tiny injuries such as treading on a shell, being pricked by a crab’s claws, or having water touch the incision caused by a new piercing or tattoo. One-fifth of people who get vibriosis as a result of wound infections die.

The risk is high enough that the CDC issued an advisory to health agencies and physicians on Friday afternoon, encouraging them to consider V. vulnificus if they discover of wound infections in anyone who has been in the water in the Gulf of Mexico or on the East Coast. The advisory underlines how quickly these infections can become septic and advises doctors to submit cultures to a lab—but it also wants clinicians to start patients on antibiotics right away, without waiting for lab results or consulting with a specialist.

Vibrio are spreading. In March, a study team based at the University of East Anglia in the United Kingdom used diagnostic data linked with global change models to characterize the current condition in the United States and project what would happen ahead. They discovered that cases of V. vulnificus wound infections increased eightfold between 1988 and 2018. They were recorded roughly 30 miles (48 kilometers) further north every year.

The authors then mapped the bacterium’s potential additional shift using different computer models based on expected levels of greenhouse gas emissions along with population shifts. They discovered that Vibrio, which is already present in the Chesapeake Bay, might expand its range to the center of the New Jersey shore by 2060 under a conservative low-emissions scenario. In a high-emissions scenario, it might move as far north as the coast of southern Maine by 2100.

Elizabeth Archer, an environmental scientist who led the research as a doctorate student, says it was a slight surprise to learn that V. vulnificus had already reached the outskirts of New England after hearing about recent cases in Connecticut and New York. “Our model had predicted that area to be in the main distribution of infections by mid-century,” she explains. “So it was perhaps a bit surprising that it came so soon—but also not surprising, given the trends in ocean warming and air temperatures.”

For years, some scientists have been concerned that temperature fluctuations are allowing Vibrio to spread outside its historic range. Bacterial surges have been observed on the beaches of the Netherlands and Poland, as well as on tidal flats in northern California—all locations where the water should be too cold for Vibrio to grow. Vibrio has also surged in Atlantic coastal waters off Florida and the Carolinas during the last decade, contaminating seafood and creating a risk to individuals who fish or boat in marshes and in-shore rivers.

The unusual warming of ocean water this year, which spurred Hurricane Idalia’s quick intensification the night before it reached Florida’s Big Bend, is transforming marine habitats all the way up the Atlantic Coast. In recent years, both Long Island Sound (where two of the Connecticut patients were apparently infected) and the waters off New England have reached record-high temperatures.

“V. vulnificus is only active above 13 degrees Celsius, and then it becomes more prevalent up until the temperature reaches 30 degrees Celsius, which is 86 degrees Fahrenheit,” says Karen Knee, an associate professor and water-quality expert at American University, as well as an open-water swimmer used to ocean conditions. “I was looking at sea surface temperature maps, and everywhere south of Cape Cod is getting into territory above 20 degrees Celsius, which is when [Vibrio] really starts to become more infectious.” And it includes the majority of the swimming areas on the East Coast.”

There’s more to it than just temperature changes. Changes in water quality, according to Geoffrey Scott, head of environmental sciences at the University of South Carolina’s Arnold School of Public Health and leader of an oceans and climate change research group, are amplifying Vibrio’s propensity to cause serious sickness. People relocating to coasts are driving these changes, which increases nutrient fluxes into the ocean via wastewater.

Vibrio used to be a late-summer threat, but it is increasingly appearing earlier—and later—in the year. “We’ve gone from them being primarily a problem from late July to early October to having them from April to November,” says Scott, who previously oversaw numerous coastal facilities for the National Oceanic and Atmospheric Administration. “And in some cases, they have been seen overwintering in North Carolina, around the Outer Banks.”

To the difficulties of V. vulnificus becoming more virulent in more areas for longer periods of time, you may add that more people may be exposed: first, since hot weather naturally drives more people to the beach, and second, because some of those people may be unaware of their vulnerability. “[Vulnificus] appears to affect people with liver disease much more severely than those without,” says Scott Roberts, an infectious-disease physician and assistant professor at Yale School of Medicine. “And, in general, being immunocompromised.” That could be due to old age, treatment, or if there is an underlying ailment.”

Many people will be unaware that they are in risk. Every state with a shellfish business participates in the Food and Drug Administration’s National Shellfish Sanitation Program, which establishes standards for all aspects of shellfish production, including screening for Vibrio contamination. That’s because any suspicion of the organism’s presence can shut down a state’s shellfish industry. (In fact, since the recent deaths, the Connecticut Department of Agriculture’s main page has been topped with a highlighted banner declaring that “Connecticut shellfish have never been associated with Vibrio vulnificus infections.”

However, there is no national program that can warn swimmers or surfers of the presence of Vibrio in the ocean; no testing regime like those that look for coastal E. coli; and no flag system like those that notify severe surf and rip tides. These dangers are common knowledge among those who have lived near them.

“People down here might have a friend who got cut on a shell or while fishing, and their finger is a little red and swollen, and someone will say, ‘Don’t sleep on that.'” “I had a friend who waited until the next morning and he lost his hand,” recalls Brett Froelich, an assistant professor of microbiology at George Mason University in Virginia. “Others in other places are unaware of this. They will undoubtedly think, ‘Well, I hope it gets better in the morning,’ and their hand will be black in the morning.”

This raises the question of how to make the population in newly endemic areas aware of their new hazards. No one wants to be viewed as harming seaside tourism, especially researchers at publicly financed colleges. “We don’t want to scare people away from beaches,” adds Froelich. “You don’t have to avoid them.” All you have to do is be aware.”

As The Oceans Warm, A Flesh-Eating Bacterium Is Making Its Way North

If you were planning a beach vacation this year, you may have kept an eye out for great white sharks.

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