The European Centre for Disease Prevention and Control (ECDC) has issued a warning highlighting the seasonal risk for Vibrio infection. For primary care physicians, it is becoming increasingly important to be able to recognize the signs and understand the evolving epidemiology of vibriosis.
Vibrio bacteria thrive in brackish coastal waters, where freshwater and saltwater mix, especially under high temperatures and lower salinity, conditions that are becoming more common across Europe, Therese Westrell, PhD, principal expert in food- and waterborne diseases at the ECDC, told Medscape Medical News.
Therese Westrell, PhD
While the Baltic Sea has historically been a known hot spot due to its naturally lower salt concentration, the threat is expanding. “Given the ongoing increases in sea surface temperatures across Europe, the overall environmental suitability for [non-cholera] Vibrio species could be elevated during the 2025 summer season, not only in the Baltic Sea but also in other coastal regions,” Westrell said. “Other parts of Europe could sustain conditions conducive to Vibrio proliferation, such as estuaries and enclosed water bodies with moderate salinity, in some areas of the North Sea and certain parts of the Mediterranean.”
In recent summers, Vibrio suitability models and real-time surveillance tools have indicated that areas of the North Sea coastlines of Germany and the Netherlands, as well as Mediterranean estuarine zones, can now experience intermittent periods of suitability, particularly when sea surface temperatures exceed 20 °C. “The geographic range of environmental suitability for Vibrio species is expanding, and risk periods may last longer than in previous years due to earlier seasonal warming and later autumn cooling,” said Westrell.
Also, more frequent heavy rainfall because of climate change could create new risk areas, at least temporarily, where large amounts of freshwater end up in the sea.
Who Is Most Vulnerable?
While anyone can contract a Vibrio infection, certain populations face a significantly higher risk for severe outcomes. Individuals with weakened immune systems or chronic liver conditions are particularly vulnerable. A recent article in The Lancet Planetary Health emphasized this demographic shift, noting that an aging global population with increasing chronic comorbidities, especially liver disease, is increasingly susceptible to more serious infections. For instance, data from the US CDC suggest that individuals with liver disease are 80 times more likely to become ill and 200 times more likely to die from Vibrio vulnificus infection after eating raw oysters than those without liver disease.
What Should HCPs Know?
At first glance, Vibrio infections are not distinguishable from most gastrointestinal infections presenting to primary care because most general practitioners do not have access to microbiology testing in real time, Tiago Villanueva, MD, family physician and president of the European Union of General Practitioners and Family Physicians, told Medscape Medical News. “Our priority in primary care is not so much reaching a specific diagnosis but trying to assess whether it is a case that can be managed at home with symptomatic treatment or needs to be referred to hospital. In the latter, patients may present red flag signs, such as severe dehydration, impaired level of consciousness, or acute abdomen.”
Tiago Villanueva, MD
If ingested through food or water, Vibrio can cause gastrointestinal symptoms, typically manifesting as watery diarrhea, abdominal pain, nausea, vomiting, fever, and chills. But if Vibrio bacteria enter through a wound, they can cause severe infections, including local wound infections with swelling and fever, tissue death around the wound, and potentially fatal blood infections, Westrell explained. Ear infections can also occur if the bacteria enter through the ear canal.
In the presence of these symptoms, it is essential to ask patients about their recent consumption of raw or undercooked seafood, especially oysters, and any contact with brackish or saltwater, particularly if they have open wounds, recent piercings, or cuts. Untreated wound infections can rapidly progress to serious conditions such as necrotizing fasciitis, bloodstream infections, sepsis, or even limb amputation, especially in vulnerable individuals.
Healthcare professionals (HCPs) can also educate patients, particularly those at higher risk, on prevention. “Vulnerable patients should be very cautious in terms of ordering raw or undercooked seafood in restaurants, particularly in the summer months, and maybe even avoid it altogether unless they’re very confident hygiene and food safety standards are very high,” Villanueva said. “This is particularly relevant in people — mostly from Northern Europe — coming for a holiday in Southern European countries, where seafood consumption is very high during the summer months.”
HCPs can also recommend avoiding swimming or wading in brackish or saltwater if there are open wounds, recent piercings, or cuts. If exposure is unavoidable, affected areas should be covered with waterproof bandages, and any exposed cuts or wounds should be washed immediately with clean freshwater after accidental contact with seawater.
The Surveillance Gap
Despite the increasing risk, Vibrio infections are likely underreported across the EU/European Environment Agency (EEA). “Many countries do not have mandatory surveillance in place, and clinical awareness of these infections could be relatively low, especially in regions where cases have only recently emerged,” Westrell said.
The ECDC is launching a voluntary surveillance system for vibriosis at the EU level in 2026, in collaboration with EU/EEA Member States, the EEA, and other partners in the Climate and Health Observatory. This system aims to collect detailed data on species, infection types, exposure locations, and patient outcomes and will invite countries to provide historical data to establish trends.
In the meantime, the ECDC continues to support early detection and awareness through its Vibrio Map Viewer, which uses real-time satellite data to assess environmental suitability.
Westrell and Villanueva reported having no relevant financial relationships.
Manuela Callari is a freelance science journalist specializing in human and planetary health. Her work has been published in The Medical Republic, Rare Disease Advisor, The Guardian, MIT Technology Review, and others.