Health
Understanding Waterborne Bacteria Risks for Older Adults
Health Points
- Vibrio vulnificus infections are increasing along the Gulf Coast, leading to hospitalizations and fatalities.
- Older adults and people with health conditions are at higher risk from waterborne bacteria.
- Simple steps like avoiding raw shellfish and protecting wounds can dramatically reduce infection risks.
Enjoying a summer swim or a taste of fresh oysters can be part of a healthy lifestyle, but public health officials are sounding an alarm about the rise of Vibrio vulnificus — a dangerous bacteria sometimes called “flesh-eating.” This bacteria, common in warm, salty waters, has led to dozens of hospitalizations and eight deaths this year across Gulf states like Louisiana and Florida.
Louisiana has reported 17 cases and four deaths from Vibrio vulnificus so far in 2025, while Florida counts 13 cases and four deaths. Health experts note that the bacteria is spreading northward each year, not just limited to the Gulf Coast anymore.
“Vibrio vulnificus is by far most common in the Gulf states, but it’s been expanding northwards,” explains Dr. Thomas Russo, chief of infectious disease at SUNY University in Buffalo. “As its range expands, the number of cases are likely to expand as well.”
What exactly is Vibrio? These bacteria thrive in warm coastal waters and can infect people through open wounds or by eating raw or undercooked shellfish. “Vibrio is a germ that likes to live in warm, salty waters,” says Dr. William Schaffner of Vanderbilt University. “It can contaminate beachfront areas.”
Dr. Amesh Adalja from Johns Hopkins adds, “For example, almost all oysters in the Chesapeake Bay harbor the organism.” That makes raw oysters a risky treat, especially for older adults and those with specific health conditions.
How do people get sick? Most often, infection occurs when an open wound comes into contact with saltwater or brackish water—a mix of salt and fresh water. About 10 percent get sick after eating raw shellfish. People who are immunocompromised or have conditions like diabetes or liver disease face even greater risks. “Everybody has to be concerned if they go into the water and have cuts,” says Dr. Schaffner.
While the total number of Vibrio cases in the U.S. is estimated at 80,000 annually, Vibrio vulnificus accounts for about 150 to 200. However, these numbers are climbing fast, with the area of infection expanding nearly 30 miles further north every year. “The reason it’s spreading is global warming,” Dr. Schaffner says. “This used to be an infection that was largely confined to the Gulf Coast.”
Symptoms vary depending on how infection occurs. Eating contaminated shellfish can lead to vomiting, diarrhea, and stomach pain. If the bacteria enters through a wound, it can cause fever, chills, low blood pressure, skin breakdown, and ulcers. “You can quickly develop fever, chills, and feel very poorly, very, very quickly,” Dr. Schaffner explains. Dr. Russo notes that gastrointestinal symptoms sometimes look like other mild stomach bugs, so cases can be missed.
Vibrio vulnificus is treatable, but quick action matters—a fifth of all cases are fatal, sometimes within just a day or two. “You have to assess the local site of infection very carefully because it can be subtle,” says Dr. Schaffner. Sometimes, extensive medical care or even amputation is required.
Fortunately, there are practical ways to protect yourself, especially if you’re over 40 or have medical conditions. Don’t swim if you have open wounds, fresh tattoos, or piercings. “If you have an open wound, you should really avoid going into brackish water,” Dr. Russo says.
He also strongly advises against eating raw or undercooked oysters: “Don’t eat raw oysters,” he says, reminding everyone that shellfish can also transmit other germs. And before heading out to the beach or bay, check local water alerts from health departments for any warnings.
With a little caution, you can continue to enjoy oceans, lakes, and seafood—without worry.