Flesh-eating bacteria aren’t limited to a few specific beaches. The bacterium behind most ocean-related cases, Vibrio vulnificus, naturally lives in coastal waters across the United States, particularly where water is warm and somewhat salty. About 150 to 200 infections are reported to the CDC each year, and roughly one in five people with this infection die, sometimes within one to two days of becoming ill. The risk isn’t tied to dirty or polluted water. These bacteria thrive in perfectly normal coastal environments when conditions are right.
Where Vibrio Is Most Common
The Gulf Coast has historically been the epicenter of Vibrio vulnificus infections in the U.S. Waters along Texas, Louisiana, Mississippi, Alabama, and Florida’s Gulf side stay warm for much of the year and have the brackish mix of salt and fresh water that these bacteria prefer. The vast majority of reported cases have come from this region.
But the map is changing fast. Between 1988 and 2018, wound infections from Vibrio vulnificus along the Eastern U.S. increased eightfold, from about 10 cases per year to 80. The northern boundary of reported cases shifted northward by roughly 48 kilometers (about 30 miles) every year during that period. States like North Carolina, Virginia, Maryland, Delaware, and New Jersey have all seen cases in recent years. In the summer of 2023, severe infections were reported during heat waves in three Eastern states that would not have been considered high-risk a generation ago.
Climate projections from NOAA suggest that by the 2040s and 2050s, the range of Vibrio vulnificus infections could reach as far north as the New York City metro area. By the end of the century, under moderate-to-high warming scenarios, infections could occur in every Eastern U.S. state. This isn’t a distant or theoretical concern. The expansion is already underway.
What Makes Water Dangerous
Vibrio vulnificus grows best in warm, low-salinity coastal water. The key trigger is temperature. When coastal water warms above roughly 20°C (68°F), bacterial concentrations rise sharply. The warmer it gets, the more bacteria are present. Data from Denmark showed that summers with unusually high sea surface temperatures, like 2014 and 2018, corresponded directly to spikes in Vibrio infections. In cooler northern European waters, these infections are otherwise rare.
Salinity matters too. Pure ocean water with very high salt content is less hospitable to Vibrio vulnificus than brackish water, the kind found in bays, estuaries, tidal creeks, and areas where rivers meet the sea. If you’re swimming near a river outlet or in a sheltered bay with warm, murky water, the bacterial load is likely higher than on an open ocean beach with strong currents and cooler temperatures.
Peak season runs from May through October, with the highest risk in the hottest months: June, July, and August. After a prolonged heat wave, when shallow coastal water has been baking for days, conditions are especially favorable for bacterial growth.
How Infections Happen
Vibrio vulnificus doesn’t infect through intact skin. The bacteria enter through open wounds: cuts, scrapes, recent surgical incisions, fresh tattoos, or even small nicks you might not notice. Once inside, the infection can progress rapidly. Some cases develop into necrotizing fasciitis, the condition the media calls “flesh-eating” disease, where tissue around the wound begins to die. This can escalate from a red, swollen wound to a life-threatening emergency within hours.
You can also get infected by eating raw or undercooked shellfish, particularly oysters, which filter large volumes of coastal water and concentrate the bacteria. But the wound-related infections are the ones that make headlines and the ones most relevant if you’re heading to the beach.
Who Faces the Greatest Risk
Most healthy people who encounter Vibrio vulnificus in coastal water will never develop a serious infection. The bacteria are disproportionately dangerous to people with specific vulnerabilities. Liver disease is the single biggest risk factor. People with cirrhosis, hepatitis, or alcoholic liver disease are far more likely to develop severe bloodstream infections. Other high-risk groups include people with diabetes, cancer, HIV, or any condition that weakens the immune system, as well as those taking medications that suppress immune function.
If you fall into one of these categories, even a minor wound exposed to warm coastal water can become dangerous quickly. The CDC specifically advises people at increased risk to wear protective clothing and shoes in coastal water to prevent cuts and scrapes.
How to Protect Yourself
The simplest rule: do not let coastal water get into an open wound. If you have a cut, scrape, or any break in the skin, the CDC recommends staying out of saltwater and brackish water entirely when possible. If contact is unavoidable, cover the wound with a waterproof bandage before you go in. This applies to everyday beach activities like wading, swimming, fishing, and even walking along the shoreline.
If you get a cut while you’re already in the water, clean it thoroughly with soap and fresh water as soon as you can. Watch the area closely over the next 24 to 48 hours. Rapidly spreading redness, swelling, intense pain that seems disproportionate to the wound, fever, or blistering around the site are all signs that warrant immediate emergency care. Speed matters enormously with these infections.
How to Check Your Beach Before You Go
The EPA maintains a free online tool called BEACON 2.0 (Beach Advisory and Closing Online Notification) that compiles state-reported beach monitoring data, including pollution events and advisory notices. It won’t tell you the exact Vibrio count at a given beach on a given day, but it will show you whether a beach is under an advisory or closure. Many coastal states and counties also post their own water quality updates, particularly during summer months.
Beyond official monitoring, you can make your own rough risk assessment. Warm, shallow, brackish water near river mouths or in sheltered bays carries higher risk than cold, open-ocean surf. If coastal water temperatures have been unusually high, or if you’re visiting during or just after a heat wave, bacterial concentrations are likely elevated. None of this means you need to avoid the beach altogether. It means treating warm coastal water with the same respect you’d give any natural environment that comes with real, if small, risks.