Vibrio bacteria in the Baltic Sea: What water sports enthusiasts need to know now

Severe vibrio infections have once again been reported this season. According to NDR, two people in Germany have already died in 2026 following a vibrio infection. One of the deceased had previously been staying on the Baltic Sea coast in Vorpommern-Greifswald. For water sports enthusiasts, it remains crucial not to enter the warm waters of the Baltic Sea, the Bodden or harbour waters with open or poorly healing wounds – not even just to wade whilst launching or landing a boat.

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.

The latest figures also show that, whilst case numbers are low, severe cases do occur. In June 2026, the LAGuS Mecklenburg-Western Pomerania pointed out that, over the past two years, there had been a total of ten cases of the illness amongst several million bathers, three of which were fatal. BOOTE had previously reported on Vibrio-related deaths and proper wound care reports.

​​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.

Although the overall risk is low, it increases particularly during warm spells in summer, in shallow water and following algal blooms. Vibrio bacteria occur naturally in seawater and brackish water, but can multiply rapidly at higher water temperatures. For water sports enthusiasts, this is particularly relevant at bathing spots, in lagoons, bays, harbours, shallow water areas and when launching boats. BOOTE explains more about the link to algal blooms in this article Blue-green algae on the German Baltic Sea coast.

However, there is no need to panic; nevertheless, we would like to explain the risks below.

​Five rules for water sports enthusiasts

1. Do not go into the waters of the Baltic Sea, the Bodden or harbour waters if you have open or poorly healing wounds.
2. Wear bathing shoes when launching a boat, wading or swimming.
3. Clean and disinfect minor wounds, then cover them with a waterproof dressing.
4. After contact with water, watch out for severe pain, redness, swelling, a fever or chills.
5. If you experience any symptoms, seek medical attention immediately and mention that you have been in contact with sea water or brackish water.

Why the Baltic Sea is particularly vulnerable in summer

In the Baltic Sea and in the Bodden waters, Vibrio bacteria find favourable conditions during warm summer periods. The bacteria multiply particularly well at higher water temperatures and moderate salinity levels. A study carried out in the Baltic Sea and the Schlei in 2025 showed that vibrio bacteria were detectable in almost all the samples analysed, although the concentrations were largely within the expected range. BOOTE has summarised the results here: Vibrio bacteria in almost all samples.

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 point of entry. 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 precautions when boating

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 motorboat owners, this applies not only when swimming from the bathing platform. Minor cuts and grazes can also occur when launching the boat, manoeuvring in shallow water, landing a dinghy, walking barefoot on the jetty or working on the trailer. Anyone with blisters, scratched mosquito bites, cuts or poorly healed areas of skin should cover them with a waterproof dressing or avoid contact with water from the Baltic Sea, the Bodden or harbour waters.

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.

​Important when seeing a doctor: You should mention this straight away if you have been in contact with sea water or brackish water. If you experience unusually severe pain from a small wound, rapid reddening, swelling, blistering, a fever or chills, do not wait – seek medical attention immediately.

Early warning using AI and drones

The Leibniz Institute for Baltic Sea Research in Warnemünde is now working on a more accurate early-warning system for Vibrio risks. According to the institute, AI models can be used to predict the occurrence of Vibrio vulnificus, in some cases several weeks in advance. Since 2026, a AI-supported drone survey programme tested for use in local warning systems.

Among other things, the drones monitor environmental factors such as water temperature, salinity, current conditions and algal blooms. The aim is to produce a local risk assessment that authorities and bathing sites could use more effectively in future. For boaters, this is no substitute for exercising their own caution, but it can help them to better assess risky periods and locations.