Climate change, hurricanes and the evolving Vibrio Vulnificus

A hidden hurricane death toll

When Hurricane Helene swept through Florida, it claimed dozens of lives. Twelve were in Pinellas County alone, eleven from drowning and one from an electrical fire caused by flooding. What those numbers don’t include is that in the following weeks five more people in Charlotte, Pasco and Pinellas counties died from infections from Vibrio vulnificusa deadly bacteria that thrives after storms.

In total, the Florida Department of Public Health reported 83 Vibrio vulnificus infections nationwide in 2024, of which more than half were linked to Helene. These infections show that the mortality caused by the hurricane is significantly underestimated – and Vibrio vulnificus poses a growing threat, driven by climate.

While the precise relationship between human-induced climate change and the frequency and intensity of hurricanes in the Atlantic basin remains uncertain, what is clear is that the speed at which storms move over land is slowing (as we saw with Hurricane Helen) and that sea levels are rising resulting in coastal flooding. Both factors increase susceptibility to storm flooding. And, it is this flood that creates the conditions for Vibrio species, including Vibrio vulnificuswhich thrives in warm and brackish environments.

Hurricanes have long been associated with Vibrio vulnificus explosions. After Hurricane Katrina made landfall as a Category 3 storm in 2005, massive flooding led to 15 cases and 3 deaths from infections within a week in Louisiana and Florida. In 2017, six cases related to Hurricane Irma were reported in Collier County, Florida—the region’s highest prior to 2022, when there were nine deaths in Lee and Collier counties related to Hurricane Ian. The increasing intensity of storms, along with rising sea surface temperatures, are now almost certainly amplifying the scale and geographic spread of these outbreaks.

What is it Vibrio vulnificus?

Vibrio vulnificus is a species of pathogenic bacteria that lives in the environment, often in association with copepods, which are small, free-swimming crustaceans. It is related to the bacterium that causes cholera (Vibrio cholerae). Vibrio vulnificus thrives in estuaries when temperatures exceed 18°C ​​and salinities range from 10-20 ppt. Typically, it infects humans through consumption of seafood or contact with contaminated water through open wounds, where it can cause sepsis. The mortality rate from sepsis can be much higher than 50%.

As the main cause of non-cholera Vibrio-related deaths globally, Vibrio vulnificus it is one of the fastest-growing diseases and imposes a significant economic toll—$238 million annually in the US alone. Climate change is now expanding the range and seasonality of Vibrio vulnificusas seen during heat waves in Sweden (2006) and Finland (2014) and in the Chesapeake Bay, where bacterial growth now often extends into the fall.

What should be done?

Rising temperatures and hydrological disasters increase the likelihood of Vibrio vulnificus infections, presenting a growing challenge to public health systems. An approach to mitigating the growing threat of Vibrio vulnificus is the development of tools for monitoring bacteria levels in vulnerable regions, especially after hydrological disasters. But monitoring is only useful if people heed the resulting warnings. Thus, educating communities about preventive measures—including avoiding exposure to water with open wounds and safe handling of seafood—is equally important.

For most people, Florida Health’s guidance is simple but life-saving: “Water and wounds don’t mix. Do not enter the water if you have fresh cuts or scrapes.”