Global warming is fostering the spread of a deadly flesh-eating bacteria along the northeastern coast of the United States, researchers report.
Vibrio vulnificus bacteria grow in warm shallow coastal waters and can infect a person via a cut or insect bite during contact with seawater. The bacteria is found as far north as Philadelphia and is spreading even further north as ocean waters warm. Between 2041 and 2060, infections may spread to waters around New York, the investigators said.
"Climate change is likely to lead to Vibrio vulnificus wound infections being found in more northern states along the U.S. East Coast. Case numbers of these serious and potentially fatal infections will increase," said lead researcher Elizabeth Archer, a postgraduate researcher at the School of Environmental Sciences at the University of East Anglia in Norwich, England.
There needs to be increased awareness of V. vulnificus infections among people who take part in coastal activities and health care professionals, she said.
"This is especially the case in Northeast states where infections are currently rare or do not occur," Archer said. "It is very important that any suspected Vibrio vulnificus infections receive medical attention quickly, as cases can become severe very quickly. Although the number of cases in the U.S. is small, someone infected with Vibrio vulnificus has a one-in-five chance of dying."
Many people who survive a V. vulnificus infection do so at the cost of an arm or leg, which often has to be amputated.
Based on models of global warming, Archer's team predicted that V. vulnificus infections will spread northwards, but how far north depends on the degree of warming, she said. If greenhouse emissions are low, then cases may extend only as far as Connecticut. If they are high, infections could spread to every East Coast state, Archer said. By the end of this century, around 140 to 200 infections may occur each year, she noted.
The number of infections caused by V. vulnificus bacteria along the East Coast have already increased — from 10 per year to 80 per year between 1988 and 2018, Archer said.
"During this time, infections were reported further north along the coastline each year," she said. "In the late 1980s, cases were rare north of Georgia, but today they can be found as far north as Philadelphia. Our models indicate that this northward movement along the East Coast will continue with sustained warming of the climate. By the middle of this century, the number of Vibrio vulnificus wound infections could double."
The findings were published online March 23 in the journal Scientific Reports.
It's not only rising water temperatures that are fueling the spread of V. vulnificus, but rising water levels as well, said Geoffrey Scott, who was not involved with the study. Scott is chair of the department of environmental health sciences and director of the NIEHS (National Institute of Environmental Health Sciences) Center for Oceans and Human Health and Climate Change Interactions at the University of South Carolina, in Columbia.
"Increased sea levels with climate change is pushing saltwater farther into their freshwater areas so there's a 230% increase in optimum growth conditions for Vibrio bacteria, which means they're going to be more available to cause illness," he explained.
Estimated infection rates are already rising, Scott said, but most cases are asymptomatic so people don't even know they were infected.
The U.S. Centers for Disease Control and Prevention acknowledges that infections are underreported, Scott said. In 2004, the CDC estimated there were 8,000 cases; by 2019, that estimate was 80,000.
Not only is V. vulnificus becoming more prevalent, but it's becoming more virulent as waters become polluted with nutrients, Scott said.
According to Scott, those most at risk for infection are overweight people who are suffering from fatty liver disease. "If you have underlying liver damage, you are much more susceptible to a Vibrio infection," he warned.
Moreover, most of the serious infections are among white men. "Most of the illnesses had been associated with consuming raw shellfish," Scott noted.
To stay safe, Scott advises people over 60 to get tested to see if they have liver damage. He also warns against eating shellfish from waters where Vibrio levels are high.
As for swimming, if you swim in the ocean where salt levels are high, there is little danger of infection, he said. But inlets, bays and sounds, which have lower levels of salt, can be breeding grounds for Vibrio and those at risk for infection should avoid swimming there.
V. vulnificus is a saltwater bacteria, so lakes and pools are safe, Scott added.
"We are trying to develop forecasts that warn the public about Vibrio," he said. "Climate change is such a big global issue, we're not going to solve it in any one country. What we can do to protect public health is to prevent exposure."
For more on Vibrio vulnificus, head to the U.S. Centers for Disease Control and Prevention.
SOURCES: Elizabeth Archer, PhD, postgraduate researcher, School of Environmental Sciences, University of East Anglia, Norwich, U.K.; Geoffrey Scott, PhD, professor and chair, department of environmental health sciences, and director, NIEHS Center for Oceans and Human Health and Climate Change Interactions, University of South Carolina, Columbia; Scientific Reports, March 23, 2023, online