July 17, 2025, 9:05 am | Read time: 3 minutes
With the summer heat, the risk of infection from Vibrio bacteria also rises—an infection 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.
Summer is in full swing, and the beaches are crowded. However, with the high temperatures, the risk of Vibrio infections also increases here 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.
How to recognize a Vibrio infection and why you shouldn’t swim even with a small injury–TRAVELBOOK provides an overview.
Where Vibrio Bacteria Lurk
According to the RKI, Vibrio bacteria 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 water’s salt content is crucial for the spread of Vibrio—in the Baltic Sea, it is particularly favorable for the bacteria at an average of 0.8 percent.
Climate Change Increases Infection Risk
A 2023 RKI study shows that ongoing climate change increases the potential for 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 can occur, 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.
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 recognized in time.
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Only a Few Cases Per Year in Germany
Overall, the registered cases are low, but likely underreported. From 2002 to 2019, the RKI recorded up to 20 Vibrio infections annually across Germany—almost all in the Baltic Sea. In 2024, a total of five Vibrio infections have been reported so far, according to Mecklenburg.
According to the institute, older people with pre-existing conditions such as diabetes, liver diseases, or cancer are particularly at risk, and children are especially vulnerable to 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 expected with ongoing climate change.”