The Berlin State Office for Health and Social Affairs has reported three cases of infection with non-cholera vibrios this season, including one fatal case. According to NDR, two people have already died. It is suspected that those affected were exposed to sea or brackish water in Mecklenburg-Western Pomerania. All three individuals were over 75 years of age and therefore belonged to a known risk group. It is particularly important for water sports enthusiasts to ensure that open or poorly healed wounds do not come into contact with water from the Baltic Sea or the Bodden.
As early as the 2025 bathing season, the State Office for Health and Social Affairs in Mecklenburg-Western Pomerania had confirmed the first vibrio infection of that season. A 68-year-old local man had become infected with the saltwater bacteria and had died despite receiving treatment in hospital. It had not been conclusively established how the man had come into contact with the vibrio bacteria. The deceased had underlying health conditions.
Case numbers remain low compared with other health risks, but the known severe cases illustrate why at-risk groups should be cautious. Last year, YACHT had already reported on a study in Schleswig-Holstein in which Vibrio bacteria in almost all the samples tested have been proven.
However, vibrio infections currently pose a very low risk to healthy people. Compared with the most common causes of death, such as cardiovascular disease and cancer, as well as road traffic accidents and suicides, the risk posed by vibrios is negligible.
However, experience shows that the generally low risk is currently on the rise again, which is linked to the proliferation of blue-green algae. If these become more prevalent, an increase in vibrio bacteria can be expected shortly afterwards, as they feed on dying blue-green algae.
Individual risk depends heavily on one’s state of health, any skin injuries and the water temperature. Warm, shallow seawater and brackish water encourage the proliferation of bacteria. The European Centre for Disease Prevention and Control (ECDC) also points out that, as water temperatures rise, the Baltic Sea is one of the European regions where environmental conditions can be particularly favourable for Vibrio bacteria.
However, there is no need to panic; nevertheless, we would like to explain the risks below:
Why the Baltic Sea is a high-risk area in summer
In the Baltic Sea and the Bodden waters, Vibrio bacteria find particularly favourable conditions during warm spells in summer. The bacteria multiply mainly at higher water temperatures and moderate salinity levels. Bacterial contamination is to be expected throughout the Baltic Sea and the Bodden areas until the end of the season. The bacteria multiply particularly well at water temperatures above 20 degrees and in waters with moderate salinity. Both conditions apply to the Baltic Sea, where the water temperature in recent years has risen steadily is.
Why vibrio bacteria are dangerous
Vibrio bacteria can enter the human body in various ways. The most common route is through breaks in the skin. Even a mosquito bite that has been scratched until it bleeds can act as a gateway. If you go for a swim whilst you have a wound, the bacteria can enter the body and cause an infection. This can destroy the skin, muscles and tissue and very quickly lead to life-threatening blood poisoning (sepsis). In severe cases, this can lead to the amputation of the affected limbs. As the condition progresses, internal organs may be affected, accompanied by the formation of abscesses within the body, which in the worst-case scenario can prove fatal.
Vibrio bacteria, which cause gastrointestinal illnesses, are transmitted orally. They enter the body via the mouth, usually through contaminated drinking water and food. Consuming raw or undercooked seafood (e.g. oysters, mussels) or fish from contaminated waters can also lead to infection.
Typical risk groups include older people and those with weakened immune systems. People with underlying conditions such as diabetes mellitus, liver disease (e.g. cirrhosis, chronic hepatitis), cancer and severe heart disease are at increased risk of contracting the disease and of experiencing a severe course of the illness.
Symptoms and safety measures on board
A striking symptom of an infection is unusually severe pain, even following minor injuries. Symptoms of a vibrio infection may also include redness, swelling and blistering of the skin, accompanied by fever, chills, vomiting and diarrhoea, and in severe cases, shock. In such cases, a doctor should be consulted immediately. If detected early, a vibrio infection can usually be treated effectively with antibiotics.
Consuming contaminated food leads to severe abdominal pain and severe vomiting and diarrhoea after around 16 hours. If left untreated, this can lead to blood poisoning shortly afterwards, which, in the worst-case scenario, can cause septic shock and multiple organ failure.
As a precaution, you should check the water temperature on site every day; take particular care when it reaches 20 degrees or above. You can also find out about the water quality before going for a swim. On the Website of the Federal Environment Agency Here you will find links to bathing waters and up-to-date water quality data for each federal state.
Wearing pool shoes can help prevent injuries; even the slightest grazes, corns or blisters on your feet can leave you vulnerable.
For sailors, this applies not only when swimming, but also when launching or landing a dinghy, walking barefoot on the jetty or working in the shallow harbour waters. Anyone with minor cuts, scratched mosquito bites, blisters or poorly healed wounds should cover them with a waterproof dressing or avoid contact with the waters of the Baltic Sea and the Bodden.
You should have a shower after swimming. If you want to be absolutely sure, you can use a disinfectant solution after spending time in waters that may be contaminated with vibrio bacteria. People with skin lesions or chronic conditions should generally avoid waters in which vibrio bacteria have been detected.
Minor wounds should be treated carefully and monitored. Scratches, cuts or grazes should be thoroughly cleaned, disinfected and covered with a plaster. If the wound is healing normally, any pain, redness and swelling should subside. The wound should be dry within a few days at the latest.
Early warning using AI and drones
Scientists at the Leibniz Institute for Baltic Sea Research in Warnemünde are now working on more accurate predictions of Vibrio risks. According to the institute, AI models can be used to narrow down the occurrence of Vibrio vulnificus, in some cases several weeks in advance. Since April 2026, an AI-supported drone monitoring programme has also been undergoing trials along the coast of Mecklenburg-Western Pomerania, with the aim of enabling local risk assessments.
Drones are used to monitor, amongst other things, water temperature, current conditions, salinity and blue-green algae blooms within the bathing water zone. The aim is to create a local Vibrio environmental index using a traffic-light system. For sailors, this does not yet replace the need for personal caution, but it does show that warnings could become significantly more precise in future.
Lars Bolle
Chief Editor Digital