Flesh-eating bacteria are killing in Florida. A threat from warm seawater

Sunburn and strong currents are not the only dangers lurking for fans of sea bathing. In the U.S., several people die each year due to infection with Vibrio vulnificus, with most cases occurring in Florida. So-called flesh-eating bacteria also appear in other parts of the world, and climate change is making them more prevalent and more widely known.

A pathogen that likes warmth and salt

Vibrios are a group of bacteria that thrive in salty water with temperatures above 20°C. They are most commonly found in shallow bays, river deltas, and salt lakes. These bacteria are present not only in the water itself but also in the organisms that inhabit it – especially oysters and clams. Eating raw seafood is the second most common way, after swimming, to contract this aggressive pathogen.

Flesh-eating bacteria are primarily encountered in the Gulf of Mexico, on the eastern U.S. coast, in East Asia, and in the Black and North Seas. Unfortunately, their presence has also been repeatedly confirmed along the southern shores of the Baltic Sea. A study published in 2024 by Danish researchers indicates that Vibrio infections in the Baltic region are increasing year by year, and their occurrence often coincides with cyanobacterial blooms.

Rapid onset, high mortality rate

Vibriosis – an infection caused by one of the species of Vibrio bacteria – is a serious health threat, with a mortality rate of up to 18%. The pathogen usually enters the body through small skin injuries, such as minor cuts, scrapes, or even fresh tattoos and piercings. Swallowing contaminated water is also dangerous.

The U.S. Centers for Disease Control and Prevention (CDC) reports that symptoms of vibriosis appear within 24 hours of exposure and vary depending on the infection route, but usually include fever and chills. When contracted through a sip of seawater or contaminated oysters, the infection manifests as abdominal pain, nausea, diarrhea, and vomiting. In the case of a wound infection, symptoms include pain, redness, swelling, and discharge. V. vulnificus colonizes tissue and causes necrosis – hence the nickname “flesh-eating bacteria.”

Necrotizing fasciitis – the medical term for wound infection caused by Vibrio species – requires urgent surgical removal of affected tissue and sometimes even amputation. If left untreated, it can lead to sepsis and death.

Flesh-eating bacteria benefit from climate change

This year, by mid-July alone, Florida had recorded eleven cases of Vibrio vulnificus infections, four of which were fatal. According to CDC data, the state averages 48 cases per year, with one in four resulting in death. However, in 2022, following Hurricane Ian, there were 17 deaths, and last year, after Hurricanes Helene and Milton, as many as 19. Scientists link this increase in cases to the impact of storms – seawater gets pushed ashore and infiltrates freshwater systems.
But the growing intensity of hurricanes and cyclones is not the only climate-related factor favoring Vibrio vulnificus. What flesh-eating bacteria need most is warmth, and rising ocean temperatures are expanding their range and extending their active season.

A scientific study published in March this year in the journal Nature suggests that climate change could turn what was once a relatively rare infection into a global public health threat. Using artificial intelligence, researchers analyzed the RNA of these dangerous bacteria and their current global distribution. The findings clearly show that in addition to warm, slightly salty water, flesh-eating bacteria also thrive in the presence of decaying plankton – which, due to increasingly extreme weather events, is becoming more and more abundant.