July 6, 2026, 10:59 am | Read time: 3 minutes
With the summer heat, the risk of infection from Vibrio bacteria also rises here–an infection with the bacterium can be fatal in the worst case. TRAVELBOOK explains where you need to be cautious of Vibrio, how to recognize an infection, and how it is treated.
Thanks to summer temperatures, the risk of Vibrio infection increases in the North and Baltic Seas. These are bacteria that multiply rapidly at temperatures above 68 degrees Fahrenheit and can cause severe wound infections or gastrointestinal illnesses, as the Robert Koch Institute (RKI) informs.
The city of Kiel recently warned swimmers about these naturally occurring bacteria. Especially for people with open wounds, a Vibrio infection can become a risk. In recent years, these bacteria have repeatedly claimed lives.
How to recognize a Vibrio infection and why you shouldn’t swim even with a small injury–TRAVELBOOK provides an overview.
Where Vibrio Lurk
According to the RKI, Vibrio are found “worldwide in both fresh and saltwater, such as in river mouths/bays, lagoons, brackish water, and also in inland lakes.” The risk of infection is particularly higher in stagnant, shallow areas that warm up quickly.
Infections have also been reported from Sweden, Finland, Denmark, Norway, the Netherlands, the Channel Islands, and the Polish coast. There are also reports of Vibrio from the U.S., Israel, Spain, Greece, Tunisia, and Turkey. The spread of Vibrio is significantly influenced by the water’s salt content–in the Baltic Sea, with an average of 0.8 percent, conditions are particularly favorable for the bacteria.
Climate Change Increases Infection Risk
A 2023 RKI study shows that ongoing climate change increases the potential for rising human health risks from waterborne infections and intoxications. It further states that non-cholera Vibrio naturally occur in seawater but can multiply significantly in shallow water at elevated temperatures.
An infection is possible, for example, when a not fully healed wound comes into contact with pathogen-contaminated seawater. This can lead to purulent inflammations that “urgently require surgical treatment.” Consuming raw or insufficiently cooked seafood and fish can also lead to a gastrointestinal infection with Vibrio.
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The Disease Can Be Fatal
The RKI warns of a possible wound infection: “An early symptom is local pain that seems disproportionately strong given the visible wound. Fever, chills, and sepsis can also occur. Surgical treatments up to limb amputation may be necessary. Severe illnesses can be fatal.”
Regarding a possible gastrointestinal illness, it states: “Gastroenteritic infections cause cramp-like abdominal pain, vomiting, nausea, and watery diarrhea. The course is usually mild overall. In severe cases, sepsis can also occur. If sepsis is not recognized and treated with antibiotics in time, it can lead to multiple organ failure and/or septic shock, which can be fatal.” Theoretically, an infection through the ears is also possible. However, successful treatment with antibiotics is possible if detected early.
Increasing Cases in Germany
According to the RKI, Vibrio infections remain relatively rare but are likely often underdiagnosed. Since 2020, there has been a reporting requirement for acute infections. While 13 cases were reported to the RKI in 2020, by 2024, 42 people had apparently been infected in Germany.
According to the institute, older people with pre-existing conditions such as diabetes, liver diseases, or cancer are particularly at risk, as are children with ear infections. The known illnesses typically occurred from June to September.
According to the RKI, the Baltic Sea will continue to be particularly affected: “An increase in infections from non-cholera Vibrio, especially in the coastal waters of the Baltic Sea, is to be expected with ongoing climate change.”