10/08/2025 | Press release | Distributed by Public on 10/08/2025 04:05
In 2025, and as of 3 September 2025, 9 countries in Europe reported 652 locally acquired human cases of WNV infection with known place of infection. The earliest and latest date of onset were on 2 June 2025 and 26 September 2025, respectively. Locally acquired cases have been reported by Italy (714), Greece (91), Serbia (60), France (42), Romania (36), Spain (23), Hungary (11), Croatia (4), Albania (3), North Macedonia (2), Bulgaria (1), Kosovo* (1) and Türkiye (1). In Europe, 63 deaths were reported.
Case numbers reported so far this year are above the average for the past decade in the same period (687). However, these figures remain lower than those seen in 2018, 2022, and 2024 - years when virus circulation was particularly intense, with over 1 200 cases reported by this point in the year. As the latter figures are based on consolidated data, while the current year's data remain delayed and incomplete, direct comparisons should be made with caution.
Italy is currently experiencing a large outbreak, with 714 confirmed human infections, including 48 fatalities (case fatality rate of 6.7%, which is within the expected range). This is the highest number of human WNV infections reported by Italy at this time of the year. The cases have mainly been reported from the Lazio region (Latina, Roma and Frosinone), with a total of 252 cases, and the Campania region (Napoli, Caserta, Salerno and Avellino), with a total 124 cases. Other regions are reporting similar numbers as in previous years.
As of 3 October 2025, locally acquired human cases of WNV infection have been reported in 139 regions across 13 countries. This compares with 179 regions (18 countries) during the same period in 2024. All 13 countries have previously reported human cases of WNV.
During the current transmission season, 35 regions reported human cases of WNV infection for the first time ever: by Italy in Genova (ITC33), Sondrio (ITC44), Avellino (ITF34), Brindisi (ITF44), Catanzaro (ITF63), Reggio di Calabria (ITF65), Palermo (ITG12), Messina (ITG13), Siracusa (ITG19), Nuoro (ITG2E), Sud Sardegna (ITG2H), Grosseto (ITI1A), Massa-Carrara (ITI11), Arezzo (ITI18), Siena (ITI19), Latina (ITI44) and Frosinone (ITI45); by France in Paris (FR101), Hauts-de-Seine (FR105), Seine-Saint-Denis (FR106), Val-de-Marne (FR107), Val-d'Oise (FR108), Lot-et-Garonne (FRI14), Haute-Garonne (FRJ23), Puy-de-Dôme (FRK14), Ardèche (FRK22) and Vaucluse (FRL06); by Greece in Irakleio (EL431) and Lakonia, Messinia (EL653); by Spain in Alicante/Alacant (ES521) and Almería (ES611); by Croatia in (HR035); by Kosovo* in Pejë (XK003); by Romania in Sălaj (RO116); and by Türkiye in Çanakkale (TR222).
As observed in previous years, most cases are among males aged 65 years and older. The hospitalisation rate is similar to previous years, with 88% of cases hospitalised this year compared to 91% in the past decade. The high hospitalisation rate is due to the nature of WNV surveillance, which tends to predominantly capture the most severe cases. The case fatality rate so far this year is 7%, which is below but comparable to the 10% observed in the previous decade. Neurological manifestations were reported in 56% of cases this year, compared to 67% in the previous decade. In general, a dominance of neurological cases is expected, as cases with more severe symptoms are more likely to be diagnosed.
From the veterinary perspective, 127 WNV outbreaks among equids and 217 outbreaks among birds have been reported in Europe in 2025. The earliest start date of an outbreak among equids and birds was on 15 January 2025 in Germany and 16 February 2025 in Italy, while the latest onset of an outbreak among equids and birds was, respectively, on 23 September 2025 in Hungary and 26 September 2025 in Germany. Outbreaks among equids were reported by Italy (59), France (37), Croatia (10), Hungary (7), Germany (5), Greece (4), Spain (4) and Austria (1). Outbreaks among birds were reported by Italy (192), Germany (15), Belgium (3), Spain (3), Austria (2), Croatia (1) and Hungary (1).
In the Animal Disease Information System (ADIS) database, no information was provided on the exact equid species reported, whereas species details were available for birds. The bird species associated with the highest number of reported outbreaks in 2025 were the carrion crow (47) and the common magpie (40), followed by the common wood-pigeon (16), common kestrel (15), herring gull (9), unidentified Accipitridae (9), hooded crow (8), little owl (6) and northern goshawk (6). In addition, several other bird species were involved in between one and four outbreaks.
In June, July, and August 2025, the number of outbreaks in equids exceeded the 10-year average (2015-2024) for those months, while the number of bird outbreaks remained below the three-year monthly mean (2022-2024) for most months, with the exception of August 2025. However, these figures were generally lower than those observed during the same period in 2024, a year marked by particularly intense WNV circulation.
As of 3 October 2025, outbreaks in birds and/or equids have been reported in 95 regions across nine countries. Of the nine countries that submitted data in 2025, eight had previously reported WNV outbreaks in birds and/or equids in previous years, reflecting endemic WNV activity in these territories. In contrast, Belgium reported WNV outbreaks for the first time ever to ADIS in 2025, with three outbreaks in wild birds. Two outbreaks involved Eurasian jackdaws, and one involved carrion crows, all recorded in August 2025. These outbreaks occurred in the administrative units of Mechelen (BE212) and Halle-Vilvoorde (BE241). Additionally, outbreaks in birds and/or equids were reported for the first time to ADIS in 23 regions: by Italy in Arezzo (ITI18), Caltanissetta (ITG15), Firenze (ITI14), Foggia (ITF46), Frosinone (ITI45), L'Aquila (ITF11), Lecco (ITC43), Reggio Calabria (ITF65), Siracusa (ITG19), and Sondrio (ITC44); by France in Haute-Garonne (FRJ23), Loiret (FRB06), Oise (FRE22), Paris (FR101), Val-de-Marne (FR107), Vaucluse (FRL06), and Yvelines (FR103); by Croatia in Koprivničko-križevačka županija (HR063), and Bjelovarsko-bilogorska županija (HR021); by Spain in Almería (ES611) and Menorca (ES533); by Austria in Innsbruck (AT332); and by Germany in Rhein-Neckar-Kreis (DE128). Furthermore, in 2025, outbreaks in equids were reported in the Greek region of Thasos-Kavala (EL515), marking the first such report in animals since the last recorded outbreak 12 years prior.
Reports of WNV outbreaks during the winter, when mosquito activity is minimal, should be carefully evaluated as they raise questions about the timing of infection. Two such reports - one outbreak in equids reported by Germany in January, and one in birds reported by Italy in February - warrant cautious interpretation, as they may reflect residual detection (e.g. lingering antibodies or viral RNA from infections acquired in the year before) rather than active transmission in 2025.
Six countries - Italy, Croatia, France, Greece, Hungary, and Spain - reported both WNV human cases and outbreaks in equids and birds. As of 3 October 2025, Italy alone accounted for 72% of all reported human cases and for 73% of all reported outbreaks in equids and birds, underscoring the significant WNV activity in some parts of the country. This is likely due to favourable climate conditions and ecological hotspots (e.g. wetlands, agricultural areas) that influence mosquito vector populations and the distribution and behaviour of animal hosts. Intensive surveillance in Italy may also contribute to high detection rates of human cases and outbreaks in birds and equids.
The reporting of WNV outbreaks in birds marks the first detection of the virus in Belgium. Notably, the country has never recorded any locally acquired human cases. This development signals a significant step in the local emergence of WNV and points to a likely recent introduction of the virus into the national ecosystem. These findings underline the need for enhanced surveillance and increased public health preparedness.
The identification of WNV cases in humans and animals within previously unaffected areas underscores the ongoing geographic expansion of the virus, which is most likely due to environmental, climatic and ecological changes. In addition, increased surveillance or monitoring sensitivity and raised awareness in these areas might play a role in the detection of the cases.
Owing to delays in diagnosis and reporting, as well as the fact that most of the WNV infections are asymptomatic or subclinical, the case numbers provided in this report likely underestimate the true number of cases. Of note, the seasonal surveillance in humans primarily focuses on capturing laboratory-confirmed cases, which contributes to the diagnostic delay.
Given that the weather conditions are becoming less favourable for WNV transmission in Europe, the number of human cases and outbreaks in equids and birds is expected to decrease in the coming weeks. In previous years, the peak of transmission was observed in August-September.