WHO warns of West Nile fever in Southern Europe: 81 cases recorded on the continent

Italy is by far the most affected country, with 46 cases recorded by the ECDC up to the previous Wednesday, spread across some twenty regions, including the major metropolitan areas of Milan and Rome and their surrounding areas. The WHO had previously reported 21 confirmed cases in Italy, but the number has since more than doubled, a sign of the virus's rapid spread in just a few weeks. Greece ranks second with 21 cases recorded since the start of the year, including 14 confirmed during the previous week alone. Among the Greek patients, 13 were still hospitalized, and three of them were in intensive care, according to the Greek national public health authority.

The European picture is rounded out with five cases in North Macedonia, five more in Romania, three in Spain, and one in France. The geographic distribution, from south to north of the continent, highlights the virus's potential for spread, taking advantage of the warm season to multiply in populations of vector mosquitoes.

How is the virus transmitted?

The West Nile virus is primarily transmitted between mosquitoes and birds, according to information provided by the WHO. However, infected mosquitoes can transmit the pathogen to humans, most frequently between July and September, a period that coincides with the current peak in infections. Longer and hotter summers, caused by climate change, increase the possibility of contamination, the international health organization points out.

In humans, the infection most often goes unnoticed. « Die meisten Menschen bemerken die Ansteckung zufolge nicht », the WHO recalls, echoing the position of researchers. When they do appear, symptoms develop two to fourteen days after the infectious bite and resemble those of the flu: fever, headaches, body aches. The Robert Koch Institute (RKI) estimates that about one-fifth of those infected develop such flu-like symptoms. In severe cases, the virus can cause diseases of the central nervous system, including encephalitis and meningitis, which can be fatal.

Symptoms and severe forms

The WHO Regional Director for Europe, Hans Henri Kluge, issued a solemn appeal to the public and health professionals: « Wer nach einem Mückenstich hohes Fieber, Hautausschlag oder Nackensteifigkeit entwickelt, sollte unverzüglich einen Arzt aufsuchen ». This recommendation aims to prevent neurological complications by encouraging early diagnosis and prompt care.

The WHO also recommends that travelers and residents of affected areas protect themselves against mosquito bites. The recommended measures include wearing covering clothing, using insect repellent sprays, and installing mosquito nets. « Zudem solle man sich auf Reisen durch Kleidung, Anti-Mücken-Sprays oder andere Hilfsmittel schützen », the organization specifies, adding that the risk of severe forms remains low for the majority of the population, including those most exposed.

WHO recommendations for travelers

The WHO's European regional office, headquartered in Copenhagen, also stresses the likely existence of a high number of unreported cases. Researchers anticipate significant underestimation of the true incidence, due to the often asymptomatic nature of the infection. This « Dunkelziffer » complicates accurate assessment of viral circulation and the planning of public health measures.

European health authorities are monitoring the situation closely. The combination of longer summers, intense tourist mobility, and the presence of the mosquito vector in many regions creates the conditions for geographic expansion of the transmission hotspot. Human cases could appear in areas previously spared if viral circulation intensifies in populations of migratory birds, the natural reservoirs of the virus, on the continent.

An underestimated toll and surveillance challenges

For healthcare professionals, the WHO emphasizes the need to remain vigilant and to promptly report any suspected case, particularly in patients with neurological complications. The organization also recalls that Belgium, Bulgaria, Croatia, France, Greece, Hungary, Italy, Romania, and Spain have already experienced local transmission episodes in previous years, a sign that the virus is now established in the Mediterranean basin.

The health agency also recommends that local authorities strengthen entomological surveillance, map larval breeding sites, and, where appropriate, carry out targeted mosquito control operations. Anti-vector measures remain the primary collective prevention strategy, in the absence of a specific vaccine for the general population and of antiviral treatment targeting the West Nile virus.

Beyond the health consequences, this alert highlights the growing impact of vector-borne diseases in Europe. Culex mosquitoes, the main vectors of the virus, are extending their range northward, taking advantage of rising temperatures and urbanization. European health authorities fear that the 2026 season, already marked by intense viral activity, may only be a prelude to more extensive waves of contamination in the years to come, as long as climatic and environmental conditions remain favorable for the tiger mosquito and its cousins.

Health outlook for summer 2026

For travelers planning to visit Italy, Greece, Spain, southern France, or the Balkans, the recommendations remain simple: apply a skin repellent, sleep under a mosquito net, wear long and light-colored clothing during mosquito activity hours (dawn and dusk), and consult promptly in case of fever or neck stiffness following a bite. « Bei hohem Fieber, Ausschlag auf der Haut oder einem steifen Nacken solle man unverzüglich einen Arzt aufsuchen », the WHO insists, a guideline particularly crucial as the seasonal peak in infections approaches.

Experts finally note that the majority of infections resolve favorably without specific treatment, but that elderly people, the immunocompromised, and patients with chronic diseases are at increased risk of complications. Targeted information for these vulnerable populations is among the priorities of the WHO and national health authorities for the coming weeks, as summer is in full swing and vector mosquitoes remain particularly active until the end of September.