An uptick in vibrio cases in the Chesapeake Bay region may be the result of the warming waters from climate change. In our partnership with the Bay Journal Delmarva Public Media's Don Rush talks with associate editor and senior writer Tim Wheeler about the significance of the increase. The full interview can be heard on this Friday's Delmarva Today at noon on WSDL and WESM.
Health officials are reporting a sharp increase in Vibrio infections across Maryland and Virginia, prompting renewed attention to the bacteria's growing presence in the Chesapeake Bay as warmer water temperatures extend its season.
According to Bay Journal Associate Editor and Senior Writer Tim Wheeler, more than 400 cases of Vibrio infections were reported in the two states during 2025. While the bacteria occur naturally in coastal waters, Wheeler said only a small number of the more than 80 known species pose serious risks to human health.
“The number of cases reported to the health departments in Maryland and Virginia has roughly doubled,” Wheeler said, noting that infections are commonly linked to consuming raw or undercooked shellfish and fish. Some species, however, can enter the bloodstream through cuts or open wounds, leading to potentially life-threatening infections.
The Chesapeake Bay provides favorable conditions for Vibrio growth. Wheeler said the bacteria flourish in warm, moderately salty water, with nutrient-rich conditions further supporting their spread. The traditional risk period between May and October has also begun expanding. “The bay's waters have gradually been warming,” Wheeler said. “As a result, the number of infections has been increasing and they've been occurring during earlier and later times of the year too.”
Despite the increase, Wheeler emphasized that the risk remains manageable. Thoroughly cooking seafood significantly reduces the chance of food borne illness, while people with open cuts should take extra precautions before entering the water.
Vibrio infections have also been reported further north along the Atlantic coast, including New England, as warming coastal waters expand the bacteria's range beyond the Chesapeake Bay.
