Infections caused by a type of deadly, flesh-eating bacterium are becoming more common and widespread as ocean temperatures rise because of climate change. And without intervention to halt global warming, such cases are likely to continue increasing and spreading, according to a paper published Thursday in the journal Scientific Reports.
The study focuses on Vibrio vulnificus, a microorganism that thrives in warm, shallow, slightly salty waters, including along the East Coast of the United States. When humans go swimming or wading, the bacteria can find their way into wounds, cuts and even insect bites; people can also accidentally ingest V. vulnificus and other Vibrio species while eating raw or undercooked seafood, such as oysters.
V. vulnificus numbers tend to peak at the height of summer. They might also rise when sewage spills into coastal waters, which is what authorities say likely happened when Hurricane Ian struck Florida last year, followed by an uptick in V. vulnificus infections.
The immune systems of healthier people can often fight off one of these bacterial infections, however, elderly people and others who are more susceptible to illness may become seriously sick. V. vulnificus can cause watery diarrhea, fever, chills, low blood pressure, blistering skin lesions, nausea and vomiting. When the bacteria get into an open wound, they can kill off otherwise healthy tissue via a phenomenon known as necrotizing fasciitis.
To understand the bacteria’s prevalence and reach, the researchers analyzed U.S. Centers for Disease Control and Prevention statistics on V. vulnificus infections reported along the East Coast between 1988 and 2018.
In the past, V. vulnificus cases have typically occurred along the Gulf of Mexico and the southern coast of the Atlantic Ocean but were uncommon in the waters north of Georgia. However, over the last 30 years, these infections have been expanding farther and farther north, reaching latitudes as high as Philadelphia while still occurring in southern states like Texas. The number of cases has also increased from ten per year in the late 1980s to around 80 per year by 2018, scientists report.
Together, the findings outline the “effect that climate change is already having on human health and the coastline,” study co-author Iain Lake, an environmental scientist at the University of East Anglia in England, says in a statement.
The researchers also modeled the bacteria’s fate under different climate scenarios. Under medium to high future greenhouse gas emissions, V. vulnificus infections will be present in every state along the East Coast between 2081 and 2100, they predict. If emissions are lower, however, the bacteria might be less widespread and only reach as far north as Boston, per the paper.
Though overall infection numbers remain low, scientists are concerned because the mortality rate of V. vulnificus is high: Around 20 percent of people who become infected die. Beyond that, some people who become infected need to have their limbs amputated.
“The infection can proceed incredibly fast: I worked with one woman whose husband was infected and it went from looking like a spider bite to necrotizing fasciitis within four hours,” says William Schaffner, an infectious disease specialist at Vanderbilt University who was not involved in the study, to USA Today’s Elizabeth Weise.
The U.S. has a growing population of elderly individuals, who may be more vulnerable to the harmful pathogen, per the study. And V. vulnificus infections are notoriously expensive to treat, costing an estimated $320 million per year across the nation.
Overall, the findings suggest the need for more proactive public outreach about V. vulnificus, scientists say, especially if ocean temperatures continue to rise in the future.
“It’s critical to get out public health messaging, such as when it’s not advisable to swim or when you should avoid these waters if you have an open wound,” says Amy Sapkota, an environmental health scientist at the University of Maryland who was not involved in the study, to NBC News’ Denise Chow. “We need to get these types of messages out to recreationalists, as well as people whose livelihoods are based on being out on the water.”