Before the summer of 2017, physicians at Cooper University Hospital in Camden, New Jersey had only seen one case of the severe, occasionally flesh-eating, disease Vibrio vulnificus.
Since then, they’ve seen five patients infected with the disease, and research released Monday suggests the cases are linked to a warming ocean. More cases are likely incoming.
It’s explained the journal Annals of Internal Medicine that in the United States, V. vulnificus is endemic along the southeastern coast and is sometimes reported in the Chesapeake Bay. But the illness has rarely been linked to Delaware Bay and the shores of New Jersey, where the water is colder — until now.
How Do People Get Vibrio vulnificus?
People become ill when the bacterium enters an open wound — likely happening when a person swims in contaminated marine water — or from eating raw or undercooked shellfish. V. vunificus is just one of the diseases caused by Vibrio bacteria but it’s the deadliest: While most people with a mild case recover in three days, a serious infection can lead to limb amputation. Worldwide, it’s the most fatal food-borne disease, with a 50 percent fatality rate. One of the patients treated in New Jersey died, while the others recovered from ailments including vomiting, fever, and a skin rash.
Madeline King, PharmD., a professor clinical pharmacy at the University of the Sciences in Philadelphia and co-author of the study, tells Inverse that she and her colleagues knew there had to be a reason why they were seeing V. vulnificus infections in patients who were exposed to seafood, or were wading in the Delaware Bay.
The manner of how patients became ill varied, but each illness was connected to those factors.
In one case, a 46-year-old became infected after going crabbing, and a 64-year-old was infected after cutting his leg on a crab trap in the Delaware Bay. Meanwhile, a 60-year old went crabbing, ate the crabs, and became sick. A 38-year-old man never went to Delaware Bay, but became sick after eating seafood sourced from there. The man who died, also 64, also became infected after cleaning crabs from the Bay with his hands.
Why Men are Frequently Victims of V. vulnificus
Men are most frequently the victim of the disease. James Oliver, Ph.D., tells Inverse that about 80 percent of the victims are male and over the age of 40. Oliver was not affiliated with this study and is an expert in the study of V. vulnificus.
“This [the frequency of male victims] appears to be because this is the major group of individuals who develop cirrhosis,” Oliver says. “It also appears that estrogen protects females, to some extent, from the toxin V. vulnificus produces.”
Alcoholic cirrhosis damages the liver, which is the body’s storehouse for the iron. That’s of interest to the bacterium: V. vulnificus only affects people with certain underlying diseases, primarily those that elevate the level of iron in the blood. Iron is essential for the bacterium’s growth, Oliver explains, and “normal” people don’t have enough free iron in the blood to allow this growth. Without elevated levels of iron, the bacterium can’t survive, even if it enters through a wound.
Why Is V. vulnificus Spreading to New Areas?
But this still leaves the question of what is this bacterium doing in the Delaware Bay?
King and her colleagues believe that the geographic spread is likely linked to the significant increase in sea surface temperatures in many of the country’s coastal regions. These, they write, are connected to “longer summer seasons and … alterations in the quantity, distribution, and seasonal windows of bacteria.”
“V. vulnificus prefers warmer, brackish waters, which is why warmer sea temperatures in our region would influence the presence of this bacterial species,” King says.
Previous studies have established a link between sea surface temperature and the spread of vibrios and, in turn, recent data has shown that incidences of Vibrio-associated illnesses are increasing worldwide. Most of these cases were reported during heat waves and, scientist note, heat waves are likely to increase in frequency and intensity as the climate crisis persists.
Oliver also points out that V. vulnificus is emerging in watery areas that were typically too cold for it to survive — frigid bodies like the Baltic Sea and off the coast of Sweden. The warming of the oceans also results in sea ice melt, which dilutes the salinity of the water. V. vulnificus requires salt but the level of salt in the open ocean water is too high for it to thrive. However, the dilution of the sea by fresh water has lowered salt levels meaning that it’s become easier for the V. vulnificus to survive and grow.
King hopes this new study helps “support the idea that warmer sea temperatures are likely affecting bacterial species” and additionally helps clinicians in areas were Vibrio wasn’t previously endemic, but could drive an increase in infections as water temperatures warm.
Oliver, meanwhile, is blunt in his advice, noting that “public information is critical and the more people learn of this, the less likely they will develop a V. vulnificus infection.”