Climate Change, Hurricanes, And Emerging Vibrio Vulnificus

A Hidden Death Toll from Hurricanes

When Hurricane Helene swept through Florida, it claimed dozens of lives. There were twelve in Pinellas County alone, eleven from drowning and one from an electrical fire caused by flooding. What these numbers don’t include is that in subsequent weeks another five people in Charlotte, Pasco, and Pinellas counties died due to infections from Vibrio vulnificus, a deadly bacterium that thrives in the aftermath of storms.

In total, the Florida Department of Public Health reported 83 Vibrio vulnificus infections statewide in 2024, of which more than half were linked to Helene. These infections show that hurricane-induced mortality is significantly undercounted—and Vibrio vulnificus poses a growing, climate-driven threat.

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 down (as we saw with Hurricane Helene) and that sea levels are rising resulting, in coastal inundation. Both factors increase vulnerability to flooding from storm surges. And, it is this flooding that creates the conditions for Vibrio species, including Vibrio vulnificus, which thrives in warm, brackish environments.

Hurricanes have long been linked to Vibrio vulnificus outbreaks. After Hurricane Katrina made landfall as a Category 3 storm in 2005, heavy 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 before 2022, when there were nine deaths in Lee and Collier counties associated with Hurricane Ian. The increasing intensity of storms, coupled with rising sea surface temperature, are now almost certainly amplifying the scale and geographic spread of these outbreaks.

What is Vibrio vulnificus?

Vibrio vulnificus is a species of pathogenic bacteria that lives in the environment, often in association with copepods, which are tiny 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 seafood consumption or contact with contaminated water via open wounds, where it can cause sepsis. Mortality rates from sepsis can be well above 50%.

As the leading cause of non-cholera Vibrio-related deaths globally, Vibrio vulnificus is one of the fastest-progressing diseases and imposes a significant economic toll—$238 million annually in the US alone. Climate change is now extending the range and seasonality of Vibrio vulnificus, as seen during heatwaves in Sweden (2006) and Finland (2014) and in Chesapeake Bay, where the bacterium's growth now often extends into the fall.

What should be done?

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

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

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