Deadly Snail Fever Outbreak Spreads to Mediterranean Vacation Hotspots

Public health officials have raised alarms as schistosomiasis, a potentially deadly parasitic disease traditionally confined to tropical regions, continues to spread in Corsica and has now been detected in other popular Mediterranean vacation destinations, raising concerns about new transmission zones in southern Europe during the busy upcoming summer tourist season.

The disease, also known as bilharzia or snail fever, has established a sustained presence in freshwater rivers and lakes across the French island of Corsica since 2013, with new cases identified among tourists and locals in neighboring Sardinia and along parts of mainland Italy’s coastline, according to recent epidemiological surveillance reports.

Unprecedented European Outbreak Enters New Phase

“This outbreak shows how easily and rapidly urogenital schistosomiasis can be introduced and spread into novel areas where Bulinus snails are endemic,” according to researchers led by Dr. Jerome Boissier at the University of Perpignan, who published their findings in The Lancet Infectious Diseases, highlighting the disease’s unexpected emergence in European waterways.

The ongoing transmission in Corsica, particularly in the Cavu River, a popular swimming destination, represents the first sustained schistosomiasis outbreak in Europe in decades. What initially appeared to be a limited, isolated event has now entered its twelfth year, with new cases detected during summer 2024 and spring 2025, demonstrating the parasite’s successful establishment in Mediterranean environments.

More concerning to epidemiologists is evidence that the parasite has spread beyond Corsica to new water systems in Sardinia and parts of coastal mainland Italy. “The presence of this snail in Corsica, along with introduction of the parasite via human transport, made it possible for schistosomiasis to spread into a previously uninfected area,” explains Dr. Bonnie Webster from the Natural History Museum in London, in an analysis published by the Natural History Museum.

Hybrid Parasite Demonstrates Enhanced Adaptability

What makes this outbreak particularly troubling is that molecular analysis has identified the European schistosomiasis strain as a hybrid between Schistosoma haematobium, which infects humans, and Schistosoma bovis, which primarily affects cattle and other livestock. This hybrid form appears capable of infecting a wider range of snail hosts, enhancing its potential for transmission and geographic spread.

“Some patients were infected with a combination of the human and bovine species of schistosome that had bred together to form a viable hybrid,” explained Dr. Webster. “The hybrid can infect a wider range of intermediate snail hosts, increasing the potential for schistosomiasis transmission.”

Genetic analysis conducted by researchers at the University of Perpignan traced the parasite’s origin to Senegal in West Africa, where such hybrids are prevalent. The introduction likely occurred when travelers infected in Africa visited and swam in Corsican waterways, unknowingly releasing parasite eggs that could then infect local snails and complete the life cycle.

Health Risks for Vacationers

Schistosomiasis causes serious health complications that may not become apparent until months after exposure. According to the Centers for Disease Control and Prevention (CDC), the disease affects approximately 250 million people worldwide and is second only to malaria in terms of global parasitic disease impact.

The parasites mature inside the human body, living in blood vessels where they produce eggs that can damage the bladder, intestines, liver, and other organs. While initial symptoms may include fever, rash, and muscle aches, long-term infections can lead to severe organ damage, bladder cancer, and in some cases, death.

“Schistosomiasis has an extremely high death rate. Aside from more immediate symptoms such as bloody urine and fever, patients with the disease often suffer severe organ damage later in life,” cautions the Journal of Tropical Diseases & Public Health in a review of the disease’s impact.

What makes the disease particularly insidious is the fact that many infected individuals may have mild symptoms or none at all, making it difficult to track the onward transmission of the disease. Travelers may return home unaware they’ve been infected, only to develop symptoms months later when the connection to their Mediterranean vacation is no longer apparent.

Transmission and Risk Factors

Schistosomiasis spreads when people swim or wade in freshwater contaminated with the microscopic parasite, which is released from certain freshwater snails. The parasite can penetrate human skin on contact with contaminated water, and unlike many waterborne infections, it cannot be prevented through careful drinking water habits.

The World Health Organization (WHO) explains that the lifecycle requires specific snail species that serve as intermediate hosts, and these snails have long been present throughout parts of southern Europe but had not previously been infected with the schistosomiasis parasite until the recent outbreak.

The European Centre for Disease Prevention and Control (ECDC) has identified several risk factors for travelers, including swimming in freshwater bodies in Corsica, particularly the Cavu River, as well as similar natural swimming areas in southern Sardinia and designated at-risk zones along the Italian coast.

Public Health Response

Health authorities in France, Italy, and other Mediterranean countries have implemented enhanced surveillance measures to monitor the situation. Warning signs have been posted at known transmission sites, though critics argue that these efforts have been inconsistent and often insufficient to deter tourists eager to cool off in scenic natural waterways.

Dr. Jérôme Boissier, who led the initial investigation into the Corsican outbreak, emphasizes the need for greater public awareness. “It is crucial that travelers to these regions understand that this is not just a tropical disease anymore. The risk in certain European freshwater bodies is real and growing,” he stated in a recent interview with European health officials.

The drug praziquantel remains highly effective at treating infections when they are diagnosed, and medical facilities across Europe have increased their capacity to test for and treat the disease. However, health officials stress that prevention through avoiding potentially contaminated water is the most reliable approach.

Implications for Mediterranean Tourism

The ongoing transmission has raised concerns about potential impacts on tourism, a vital economic sector for Mediterranean coastal regions. Tourism authorities and health officials are working to balance public health communications with fears of deterring visitors to otherwise safe destinations.

“We want to ensure travelers have accurate information to make informed decisions about swimming activities, without causing undue alarm about the overall safety of visiting these beautiful regions,” noted a spokesperson for the Italian Ministry of Health in a statement earlier this year.

The European regional office of the World Health Organization has established a coordinated monitoring network and is providing technical support to affected countries. Environmental management efforts, including snail control measures in high-risk areas, have been implemented, though the effectiveness of these interventions in natural water systems remains to be determined.

Health experts caution that as climate change continues to warm European waters, conditions may become increasingly favorable for both the snails and the parasite, potentially expanding the geographic range where transmission can occur.