The amount of coastal water that can harbor harmful Vibrio bacteria has spiked 56%. One species is flesh-eating.

• Rising sea temperatures are leading the habitat for Vibrio bacteria - which lives in warm, brackish water - to expand.
• The portion of coastlines in which Vibrio bacteria can thrive has risen 56% since the 1980s.

The amount of coastal water in which harmful bacteria can live has increased 56% over the past few decades, a report published Wednesday found.

That bacteria family, called Vibrio, lives in salty or brackish coastal waters, including in the US and Canada. The infection it causes, vibriosis, is usually contracted by eating raw or undercooked seafood or by exposing a wound to bacteria-infested seawater. Mild cases resolve in about three days, but Vibrio can also cause severe diseases, including gastroenteritis, life-threatening cholera, dangerous wound infections, and sepsis.

One species of Vibrio bacteria, Vibrio vulnificus, is referred to as flesh-eating because the bacteria can aggressively destroy body tissue. Those infections, though rare, often require intensive care or amputation. And they can be fatal, killing one in five infected people, usually within two days, according to the Centers for Disease Control and Prevention.

The reasons Vibrio is becoming a greater threat are that sea surface temperatures are rising and seawater is getting saltier. That's one of many alarming findings from the medical journal The Lancet's sixth annual report on health and climate change. In it, researchers from academia and the United Nations tracked 44 indicators of health effects linked to climate change.

Their conclusion: Climate change is worsening health around the globe and exacerbating existing health and social disparities.

"As the COVID-19 crisis continues, every country is facing some aspect of the climate crisis," Anthony Costello, executive director of the report, said in a statement, adding, "The Lancet Countdown's report has over 40 indicators and far too many of them are flashing red."

One of those red indicators is the link between rising sea temperatures and waterborne diseases like vibriosis. According to the report, the amount of habitable coastline for Vibrio bacteria in certain latitudes of the northern hemisphere has expanded from 7% in the 1980s to 10.9% in 2020.

Most Vibrio infections happen during the summer

Every year in the US, an estimated 80,000 people are sickened by Vibrio and 100 die from their infections. Because Vibrio bacteria thrives in warm water, 80% of those infections are contracted between May and October, according to the CDC.

The bacteria isn't just a threat to people: In April, after hundreds of dead fish washed up on shore in New Jersey, the culprit turned out to be a species of Vibrio bacteria, according to the Associated Press.

"It is suspected that if there are wider temperature swings during the fall and spring, then this could worsen the impact of these mortality events," the state's Department of Environmental Protection said.

While 100 human deaths per year is a low toll from a public-health perspective, rising sea temperatures are poised to make Vibrio - and, most likely, the infections and deaths it causes - more widespread.

Specifically,the amount of habitable coastline for Vibrio bacteria rose from 1.2% to 5.1% in the Atlantic Northeast and from 1.2% to 5.1% in the Pacific Northwest between the 1980s and 2020, the Lancet report found. During the same period, the habitable area for the bacteria in the Baltics increased from 47% to 82%.

Other concerning indicators described in the Lancet report include an increased potential for diseases spread by mosquitoes and a concerning link between extreme heat events and poor mental health, including suicidality.

When countries meet next month for the COP26 climate negotiations in Scotland, Costello said, he thinks it could be an opportunity to respond to climate change and COVID impacts simultaneously.

"We have a choice. The recovery from COVID-19 can be a green recovery that puts us on the path of improving human health and reducing inequities, or it can be a business-as-usual recovery that puts us all at risk," he said.