Flesh-Eating Bacteria Are Spreading – And Warming Seas Are to Blame

The term "flesh-eating bacteria" is technically inaccurate. But it does convey what these microorganisms do: they destroy tissue so fast that limbs must be amputated within hours. The two species most closely watched today are Vibrio vulnificus, which thrives in warm, brackish waters, and group A Streptococcus pyogenes, which spreads from person to person. Both are on the rise. And rising sea temperatures are a major reason why.

Vibrio vulnificus enters the human body in two ways: through open wounds exposed to contaminated seawater, or through the consumption of raw shellfish, especially oysters. In healthy individuals, infection is usually mild. But in people with liver disease, diabetes, weakened immune systems, or advanced age, the bacterium can trigger sepsis and necrosis within hours. According to the US Centers for Disease Control and Prevention, one in five patients with a severe infection dies within days.

Streptococcus pyogenes behaves differently. It is transmitted via the respiratory route or through skin wounds. In its most dangerous form, it causes streptococcal toxic shock syndrome, with a mortality rate of around 30 percent. Although it responds well to antibiotics such as penicillin, the number of severe cases has risen strikingly in recent years.

The recent history of Vibrio vulnificus in the United States is the best documented. Since 1988, the country has recorded more than 2,600 infections and over 700 deaths linked to this bacterium. Cases are concentrated along the southern coast, especially in Florida and Louisiana. In 2024, Hurricane Helene's landfall in September caused coastal flooding that sent infections soaring: Florida reported 82 cases and 19 deaths, record figures according to state authorities. The total number of deaths that year linked to Vibrio in Florida reached 89.

The year 2025 was no better. By August, Florida had recorded 13 cases and 4 deaths, while Louisiana had 17 hospitalised cases and 4 deaths – a 400 percent increase in fatalities compared with previous years. The most recent case occurred on July 21, 2025, when a 77-year-old man died in Mississippi after becoming infected through a scratch on his leg while working with a boat trailer.

In Asia, the focus has been different. In Japan, cases of streptococcal toxic shock syndrome reached 941 in 2023, the highest figure on record. In 2024, that number was surpassed in barely six months: Japan confirmed 977 infections before the halfway point of the year, with 77 deaths recorded. The country had been registering between 100 and 200 cases a year since 1992, which makes the recent figures particularly striking.

Europe, for its part, faces the problem from the marine front. Between 2014 and 2017, the average annual number of Vibrio infections on the continent stood at 126. In 2018, an especially hot summer tripled that to 445 cases, mainly in Baltic countries. In June 2026, as summer began, the European Centre for Disease Prevention and Control was already classifying the season as high risk. Spain is not starting from scratch: Galicia has recorded three significant outbreaks caused by Vibrio species over the past two decades, with nearly 100 people affected in 2012 after eating spoiled prawns.

The key question is why the numbers keep going up. The answer lies largely in water temperature. Vibrio thrives between 20°C and 35°C in waters with moderate salinity. Those conditions, once confined to the tropics, now extend every summer to latitudes that thirty years ago were too cold. The European Environment Agency estimates that sea surface temperatures in Europe have risen between four and seven times faster than the global ocean average. The Mediterranean, viewed by scientists as one of the regions most vulnerable to global warming, is particularly exposed. As bodies of water shrink under the effect of heat, bacterial density increases in what remains, raising the risk of exposure.

In July 2024, the European Food Safety Authority published a risk assessment with a clear conclusion: the prevalence of these bacteria in seafood is expected to increase, both in Europe and worldwide, as a consequence of climate change. The ECDC has developed a monitoring system based on satellite data on sea temperature and salinity, generating real-time risk maps. The main hotspots currently forecast are the Black Sea, the North Sea, and the Baltic.

The impact is not only on health. A beach closed in high season means immediate losses for hotels, restaurants, and tour operators. The Mediterranean is the world's most visited holiday region, which magnifies the impact of any health alert. Vibrio infections have risen by more than 84 percent globally since the early 2000s. If the trend continues, what is now a seasonal, localized risk could turn into a structural public health problem in the medium term.

As Hatim Aznague, a Climate Action and Energy Resilience analyst at the Union for the Mediterranean, put it: "The bacteria are not the story; they are the messengers. The story is a sea thrown off balance by heat and pollution."

Written by Thorben Thiede thorben.thiede@alpineweekly.com