As summer temperatures rise and heatwaves become more frequent, conditions are increasingly favorable for the growth of certain bacteria — including Vibrio. This naturally occurring bacterium thrives in coastal areas where seawater mixes with freshwater. Though it’s been known to scientists for decades, Vibrio is now appearing more widely across Europe due to climate change and rising sea temperatures — allowing it to proliferate in new regions and for longer periods each year.
What Is the Vibrio Bacterium?
Vibrio is a group of waterborne bacteria commonly found in warm or temperate waters with moderate salinity. Infections caused by these bacteria — collectively called vibriosis — typically occur in two ways: through consuming raw or undercooked shellfish (especially oysters), or when the bacteria enter the body via an open wound exposed to contaminated water.
While two specific strains — Vibrio cholerae O1 and O139 — cause cholera, most Vibrio species are unrelated to that disease.
Symptoms of Infection
Symptoms vary depending on how exposure occurs:
- During swimming or water contact: ear infections, wound infections, redness, pain, and swelling at the site of infection.
According to the European Centre for Disease Prevention and Control (ECDC), untreated wound infections can — in rare cases — progress to serious bloodstream infections, sepsis, or even necrotising fasciitis.
Particular concern surrounds Vibrio vulnificus, sometimes dubbed the “flesh-eating” bacterium. Although infections are rare, they can escalate rapidly — especially among people with weakened immune systems or chronic liver disease.
How Real Is the Risk in Europe?
Vibrio infections remain relatively rare across Europe overall. However, cases have risen notably in recent years — particularly in countries bordering the Baltic Sea following prolonged heatwaves and unusually high sea temperatures.
In 2018 alone, 445 cases were reported — more than triple the average of about 126 cases per year between 2014 and 2017, according to ECDC data.
The European Food Safety Authority (EFSA) warns that continued ocean warming is expected to increase Vibrio presence both in coastal waters and in seafood.
Who Should Be Most Cautious?
People at higher risk of severe infection include those with:
- Weakened immune systems,
- Chronic liver disease,
- Open wounds, cuts, or recent piercings.