In recent years, deaths linked to the flesh‑eating bacterium Vibrio vulnificus and group A streptococcus have risen in the US, Europe and Asia. Warming seas have allowed Vibrio to spread from the Baltic to parts of the North Sea and the Mediterranean.
Calling it "flesh-eating bacteria" is technically inaccurate, but the nickname helps to describe what it does: it destroys tissue so quickly that limbs have to be amputated within hours.
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The popular term in fact brings together several bacterial species capable of causing necrotising fasciitis, the progressive death of muscle and skin tissue. The two most closely monitored today are Vibrio vulnificus, a marine organism, and group A Streptococcus pyogenes, which is transmitted between people.
Vibrio lives in warm, brackish waters, where rivers flow into the sea, and reaches humans through two routes: contact between an open wound and contaminated water, or, more likely, eating raw shellfish, especially oysters or prawns.
In healthy people, the infection usually causes only gastrointestinal symptoms. The problem arises in vulnerable groups: patients with liver disease, people with weakened immune systems, diabetics or older people. In their case, the bacteria can trigger sepsis and necrosis in a matter of hours. According to the United States Centers for Disease Control and Prevention (CDC), one in five patients with severe infection dies within a few days.
Streptococcus pyogenes has a different biology. It is spread through the respiratory route or via skin wounds, not through seawater. In its most dangerous form it causes streptococcal toxic shock syndrome (STSS), with a mortality rate of around 30%.
Although it has been known for decades and responds well to antibiotics such as penicillin or amoxicillin, the number of severe cases has risen strikingly in recent years. The two bacteria share the same nickname, but their routes of transmission and risk profiles are different.
The latest outbreaks: from Florida to Japan via the Mediterranean
The recent track record of Vibrio vulnificus in the United States is the best documented in the world. Since 1988, the country has recorded more than 2,600 infections and more than 700 deaths linked to this bacterium.
The cases are concentrated along the southern coast, especially in Florida and Louisiana, where climatic conditions are ideal for it to proliferate. In 2024, Hurricane Helene, which hit 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, according to the state Department of Health.
The year 2025 was no better. By August, Florida had recorded 13 cases and 4 deaths, while Louisiana – where the historical average rarely exceeded one death a year – reported 17 hospitalised cases and another 4 deaths, a 400% increase in fatalities compared with previous years.
The most recent case occurred on 21 July 2025, when a 77-year-old man died in Bay St. Louis, Mississippi, after becoming infected through a scratch on his leg while working with a boat trailer. In all, eight people died from this bacterium in the US in just the first few months of that year.
In Asia, the focus of concern was different. In Japan, cases of streptococcal toxic shock syndrome caused by Streptococcus pyogenes reached 941 in 2023, a record high at the time. In 2024, that figure was surpassed in barely six months: Japan’s National Institute of Infectious Diseases confirmed 977 infections before the year was halfway through, with 77 deaths recorded. From 1992, the country had registered between 100 and 200 cases of this disease a year, which makes the recent figures particularly striking.
Europe, for its part, faces the problem from the marine side. 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 figure to 445 cases, mainly in Baltic countries: Norway, Sweden, Denmark, Finland, Poland and Estonia.
In June 2026, as summer began, so did a season that the European Centre for Disease Prevention and Control (ECDC) had already described as high risk.
Spain is not starting from scratch: Galicia has recorded three significant outbreaks caused by species of the genus Vibrio in the last two decades: 64 people were affected in 1999 after eating oysters, 80 in 2004 and almost 100 in 2012, after eating spoiled prawns. In Spain’s case, these were all infections linked to eating shellfish.
Heat as an ally: a threat that grows with rising temperatures
The most relevant question is not just how many people have died, but why the numbers keep going up. The answer lies, to a large extent, in water temperature. Bacteria of the genus Vibrio thrive between 20°C and 35°C in waters with moderate salinity.
Those conditions, once confined to tropical and subtropical coasts, now extend each summer to latitudes that, thirty years ago, were too cold for this microorganism. Jan Carlo Semenza, an epidemiologist at Umeå University in Sweden, has documented this direct correlation: the higher the sea surface temperature, the more infections there are.
The European Environment Agency estimates that sea surface temperature in Europe has risen between four and seven times faster than the global ocean average. The Mediterranean, seen by the scientific community as one of the regions most vulnerable to global warming, is particularly prone. And not only because of the temperature: the shrinking of bodies of water due to heat concentrates bacterial density in the remaining volume, increasing the risk of exposure.
In July 2024, the European Food Safety Authority (EFSA) published a comprehensive risk assessment of these bacteria and was unequivocal: their prevalence in seafood is expected to increase, both in Europe and worldwide, as a consequence of climate change.
This forecast includes the geographical spread of the bacteria to coastal areas where it is currently hardly detected. The ECDC, for its part, has developed a surveillance system based on satellite data (source in Spanish) on sea temperature and salinity that generates real-time risk maps to guide national alerts. The current hotspots are expected to be the Black Sea, the North Sea and, above all, the Baltic Sea.
The impact is not only on health. Hatim Aznague, Climate Action and Energy Resilience analyst at the Union for the Mediterranean, sums it up neatly: "The bacteria are not the story; they are the messengers. The story is a sea thrown off balance by heat and pollution." A beach closed in high season means immediate economic losses for hotels, restaurants and tour operators.
The Mediterranean is the world’s most visited holiday region, which amplifies the impact of any health alert. Globally, Vibrio infections have risen by more than 84% since the early 2000s, according to consolidated data. If the trend does not change, what is now a seasonal, sporadic risk could become a structural public health problem in the medium term.
