Dangerous Bacteria Surge due to Climate Change, UMD Researcher Finds
Photo by NASA Johnson
Hurricane Ian struck southwest Florida in September 2022, cutting a path of destruction that made it the nation’s third-costliest weather disaster and left 150 people dead in the state. But the storm’s havoc continued as it unleashed a variety of flesh-eating and other harmful bacteria in its wake that can cause illness and death in humans, according to a new study published Monday in the journal mBio.
Using a combination of genome sequencing and satellite and environmental data, a team of researchers from the University of Maryland, the University of Florida and microbiome company EzBiome detected several pathogenic Vibrio species in water and oyster samples from Florida’s Lee County, a coastal region that was devastated by Ian. The samples collected in October 2022 revealed the presence of two particularly concerning species: Vibrio parahaemolyticus and Vibrio vulnificus.
“We were very surprised to be able to detect—without any difficulty—the presence of these pathogens,” said the study’s senior author Rita Colwell, a Distinguished University Professor in the University of Maryland Institute for Advanced Computer Studies (UMIACS) who has studied Vibrio for the last 50 years.
The study’s findings correspond to a reported increase in V. vulnificus cases in the state of Florida in October 2022. According to the Florida Department of Health, Lee County, which had the highest caseload in the state, reported 38 infections and 11 deaths.
Vibrio bacteria naturally occur in the ocean, where they
live symbiotically with crustaceans, zooplankton and bivalves. When the
bacteria come in contact with humans, some species can cause an
infection known as vibriosis, but the side effects depend on the type of
Vibrio and severity of the infection. V. parahaemolyticus can cause gastroenteritis and wound infections, while the V. vulnificus species can cause necrotizing fasciitis—a flesh-eating infection—and kills 1 in 5 infected people.
People can contract vibriosis by eating raw or undercooked seafood or by getting seawater in an open wound. Because Vibrio thrive in warm saltwater, hurricanes and floods can increase the chances of a person becoming exposed.
Several conditions during and after Hurricane Ian favored the growth of Vibrio bacteria, including the amount of rainfall, changes in sea surface temperature and concentrations of chlorophyll in the ocean, which can indicate plankton blooms. In areas rich with this microscopic sea life, the researchers also found an abundance of Vibrio bacteria.
With warming oceans expected to fuel wetter and more powerful storms like Ian, coastal communities could see more Vibrio infections in the future.
“These Vibrios generally grow well between 15 and 40 degrees Celsius [59-104 degrees Fahrenheit], so as the temperature warms, their generation time shortens and they divide faster and faster,” Colwell said. “The warming of seawater—which mixes with freshwater, creating optimal salinities—really enhances the growth of Vibrios, so it’s a very serious concern.”
While the environmental conditions in Florida following Hurricane Ian were ripe for vibriosis, these cases are not limited to southern climes. In August 2023, three people in New York and Connecticut died from V. vulnificus infections.
Colwell and her co-authors—who included Kyle Brumfield Ph.D. ’23
(marine estuarine environmental sciences) and UMD cell biology and
molecular genetics Research Professor Anwar Huq—predicted this recent
spike in vibriosis cases based on trending environmental conditions in
the Northeast United States. As ocean temperatures continue to rise,
Colwell said the rapidly warming Chesapeake Bay could also be affected.
“The waters are much warmer in Florida right now than they are in the Chesapeake Bay, but on a lot of the East Coast, the waters are warming,” Colwell said. “This is a threatening indication that we may be seeing more Vibrio vulnificus infections.”
Colwell and her co-authors noted that while they analyzed only a limited number of samples, their findings illustrate the potential of genetic analysis, environmental data and remote sensing to improve public health by proactively detecting and characterizing Vibrio pathogens.
They also called for further investigation to quantify the prevalence of Vibrio
bacteria in different locations, seasons and environmental conditions.
Colwell said this research is not only vital to public health but also
an important step in understanding our changing climate.
“On the positive side, knowing that these infections are associated with the increased variability of a changing climate, perhaps now is the time to develop mechanisms to understand and mitigate it,” Colwell said. “Climate change and flooding are clearly linked to infectious disease, and we need to take it seriously.”
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