\[...\] The climate crisis is making the world’s oceans, which have absorbed more than 90% of the excess heat trapped by greenhouse gas emissions, more hospitable to Vibrio. Research shows temperature and salinity are the largest predictors of how widespread Vibrio bacteria are. As water temperatures rise, so does the concentration of Vibrio in seawater – boosting the risk of infection for beachgoers and shellfish consumers. The bacteria start getting active in water temperatures above 60F and multiply rapidly as coastal waters warm throughout the summer.

In recent years, scientists have documented Vibrio expanding into places that were once too cold to support the bacteria, pushing as far north along the US east coast as Maine and appearing with more prevalence in temperate seas around the world.

Vibriosis infections in general are the leading cause of shellfish-related illness in the US They have increased “more than any other illness caused by a pathogen in the US food supply” since the Centers for Disease Control and Prevention, or CDC, started keeping tabs on such illnesses in 1996, according to a 2019 analysis by the International Association for Food Protection. The report attributed the precipitous rise to a “perfect storm” of factors that include the climate crisis, food handling practices, expanding globalization, a patchwork of regulatory oversight and improved diagnosis.

On their conspicuous expeditions to Pensacola and other Sunshine state beaches, Magers and Kumar are trying to understand where, and when, harmful Vibrio species are present across the state. The research they’re doing is part of an ongoing effort by a laboratory at the University of Florida to create a Vibrio early warning system for the eastern US – a program that can alert public health departments to high Vibrio concentrations in any given area a month in advance.

How many limbs would be saved, Magers wonders, if doctors and nurses could be warned ahead of time that their emergency rooms would soon see an uptick in these chronically underdiagnosed infections?

\[...\]

The CDC estimates that about 80,000 cases of vibriosis occur in the US every year, resulting in about 100 deaths. Of those 80,000 cases, most are caused by a Vibrio called parahaemolyticus, which most commonly results in gastroenteritis, or food poisoning. The vast majority of the deaths, however, are caused by a type of Vibrio called vulnificus – the Latin word for “wound-making.”

Vulnificus is so potent it can squeeze through a pinhole-sized cut in the skin and lead to death within just 24 hours. In the last five years, the CDC registered 429 such vulnificus cases, plus 136 foodborne cases. But even though foodborne cases are fewer, the patients that contract vulnificus by eating contaminated shellfish are more likely to die than those infected via open wounds. Thirteen percent of those non-foodborne cases died, compared with 32% of people who got the infection from eating seafood. Most cases occur in the Gulf and Atlantic coastal regions.

As far as infectious diseases go, vulnificus is exceedingly rare: the CDC reports between 150 and 200 cases a year. The sexually-transmitted disease chlamydia, by comparison, one of the most common bacterial infections in the US, infects northward of 1.5 million Americans annually. But vulnificus’ astonishing speed and high fatality rate – 15% to 50%, depending on the health of the person exposed and the route of infection – makes it a unique public health threat, particularly as climate crisis grows its pathways of exposure.

Vulnificus is not the kind of pathogen you would want behaving erratically, but that’s exactly what it has been doing since the late 2010s. Across the eastern seaboard, local and federal health officials have been reporting “unusual increases” in vulnificus prevalence – jagged spikes in infections that appear to correspond to extreme weather events like hurricanes and marine heatwaves.

In 2022 and 2024, years when the brackish water that Vibrio bacteria thrive in was pushed inland by major hurricanes, Florida’s public health department reported 17 and 19 deaths, respectively, linked to vulnificus exposure via open wounds. North Carolina, New York and Connecticut also saw small clusters of infections during a record-breaking heatwave in the summer of 2023. “As coastal water temperatures increase,” the CDC warned in its investigation of those outbreaks, “V. vulnificus infections are expected to become more common.”

\[...\]

A 2023 study that analyzed a 30-year database of confirmed vulnificus infections from outdoor recreation along the US Gulf and Atlantic coasts found the northern boundary of infections had moved north at a rate of 30 miles a year since 1998. The study noted that “V. vulnificus infections may expand their current range to encompass major population centers around New York,” and that annual case numbers may double as temperatures rise and America’s elderly people population grows.... 

A deadly bacterium is creeping up the US east coast. How worried should we be?