European Surveillance of West Nile Virus: Monthly Report on Human and Animal Infections

West Nile Virus Cases Rise in Europe,Italy at Epicenter of 2025 Outbreak

As of August 6,2025,six European countries have reported 202 locally acquired cases of West Nile virus (WNV) infection,with Italy experiencing a meaningful outbreak. the European Center for Disease Prevention and Control (ECDC) and the European Food Safety Authority (EFSA) are closely monitoring the situation, anticipating further increases in cases in the coming weeks due to favorable weather conditions for WNV transmission.Human Cases & Geographic Spread:

Italy accounts for the vast majority of reported cases – 168,including 10 fatalities. Other affected countries include Greece (26), France (3), Romania (3), Bulgaria (1), and Hungary (1). Cases have been identified in 40 regions across these six countries. While case numbers slightly exceed the 10-year average of 163,they remain lower than those recorded in 2024 and 2018.

Notably, this year has seen first-time reports of WNV in the Italian provinces of Latina and frosinone, and in Romania’s Sălaj County, indicating an ongoing geographic expansion of the virus.The majority of those infected are males aged 65 and older. A concerning 100% of reported cases required hospitalization, with neurological symptoms present in 56% of patients. The current case fatality rate stands at 7%, consistent with past data.

Animal Outbreaks:

Alongside human cases, 16 outbreaks have been reported in equids (horses) and 20 in birds across Europe. Italy and Greece are the primary locations for equine outbreaks, while Italy and Austria have reported avian outbreaks. Outbreak numbers in both animal populations are lower compared to the same period in 2024.

Interestingly, outbreaks were detected in both equids and birds during the winter months (January and February respectively) – a phenomenon that may be attributed to residual detection from prior infections rather than active transmission.

Italy’s Central Role & Future Outlook:

Italy represents 83% of all human cases and all animal outbreaks, highlighting the country’s significant WNV activity. This is likely due to a combination of favorable climate and ecological conditions, as well as intensive surveillance efforts.

Authorities caution that reported case numbers likely underestimate the true extent of WNV infection,as many cases are asymptomatic or subclinical,and delays in diagnosis and reporting are common.

The ECDC and EFSA will continue to closely monitor the situation in Europe, emphasizing the need for continued vigilance and preventative measures as the virus continues to spread.

What specific mosquito control measures are recommended for horse owners to mitigate West nile Virus transmission?

West Nile Virus (WNV) Activity – August 2025 Update

This report details the current West Nile Virus (WNV) situation across Europe, focusing on human and animal infection data collected throughout August 2025. Surveillance data is compiled from the European center for Disease Prevention and Control (ECDC), national public health authorities, and veterinary surveillance networks.This monthly report aims to provide timely data for public health professionals, veterinarians, and the general public regarding West Nile Virus outbreaks, WNV symptoms, and WNV prevention.

Human Cases – August 2025

As of August 13, 2025, a total of 78 confirmed human cases of West Nile Virus have been reported across Europe. This represents a 15% increase compared to the same period in 2024.

Italy: Remains the moast affected country, reporting 42 cases, primarily in the regions of Lombardy, Veneto, and Emilia-Romagna. A significant proportion (60%) of Italian cases presented wiht neuroinvasive West Nile Virus, including meningitis and encephalitis.

Greece: Reports 18 confirmed cases,concentrated in the Thessaly region. Most cases (78%) are classified as non-neuroinvasive,presenting with fever,headache,and myalgia.

Spain: 8 cases reported, with a geographical distribution across Andalusia and Valencia.

Romania: 6 cases, primarily in the Danube Delta region.

Hungary: 4 cases reported.

Key Trends in Human Cases:

The majority of cases (75%) are occurring in individuals over the age of 50.

Approximately 60% of reported cases are male.

The average time between mosquito bite and symptom onset is 2-14 days.

west Nile fever is the most common presentation, but severe cases requiring hospitalization are increasing.

Animal infections – August 2025

Veterinary surveillance plays a crucial role in early WNV detection and risk assessment. Animal infections serve as sentinels for human risk.

equine Cases: 112 confirmed cases of West Nile Virus in horses have been reported across Europe. Italy (55 cases), France (28 cases), and Spain (15 cases) are experiencing the highest number of equine infections. Clinical signs include fever, ataxia, weakness, and in some cases, paralysis.

Bird Mortality: Increased mortality events in bird populations, particularly corvids (crows, ravens, magpies) and raptors, continue to be reported. Significant die-offs have been observed in Italy, Greece, and Hungary. WNV in birds is a key indicator of virus circulation.

Other Mammals: Isolated cases of WNV have been detected in sheep and goats in Italy and Spain.

Seroprevalence Studies: Ongoing seroprevalence studies in wild bird populations are revealing widespread exposure to WNV in several regions.

Mosquito Surveillance & Viral Load

Mosquito vector control is paramount in mitigating WNV transmission.

culex pipiens remains the primary vector species across most of Europe.

Monitoring of mosquito populations reveals high viral loads in Culex mosquitoes in affected areas of Italy and Greece.

Increased mosquito breeding sites due to recent rainfall are contributing to the elevated risk.

Mosquito-borne diseases are a growing concern due to climate change and increased international travel.

Diagnostic Testing & Reporting

Prompt and accurate diagnosis is essential for effective WNV management.

WNV diagnosis relies on laboratory testing of blood or cerebrospinal fluid. Common methods include PCR and serological assays (ELISA).

National public health authorities are urged to maintain high levels of vigilance and report all suspected and confirmed cases to the ECDC.

West Nile Virus testing availability and turnaround times vary across European countries.

Public Health recommendations

Personal Protection: Individuals are advised to take precautions to avoid mosquito bites, including:

Using insect repellents containing DEET, picaridin, or IR3535.

Wearing long sleeves and pants when outdoors.

Avoiding outdoor activities during peak mosquito biting hours (dawn and dusk).

Ensuring windows and doors have screens.

Veterinary Care: Horse owners should consult with their veterinarians regarding WNV vaccination and implement mosquito control measures on their properties.

Blood Donation: Individuals who have recently traveled to or resided in WNV-affected areas are advised to defer blood donation for a specified period.

Surveillance Enhancement: Continued strengthening of human