West Nile virus surge in Greece with Attica at the epicentre

Greek authorities are concerned over the West Nile virus surge in the country, with 45 new locally transmitted infections reported last week. The epidemiological picture of the West Nile virus in Greece has deteriorated significantly over the summer of 2026, with the National Public Health Organization of Greece (EODY) recording dozens of new cases in just one week and highlighting the particularly intense circulation of the virus in Attica. According to EODY’s weekly epidemiological surveillance report, with data up to 12 August 2026, a total of 110 domestically acquired cases of West Nile virus infection have been reported. Of these, 81 involved manifestations affecting the central nervous system (CNS), such as encephalitis, meningitis, meningoencephalitis or acute flaccid paralysis, while 29 cases had milder manifestations or showed no CNS involvement. The speed at which cases are increasing is a particular cause for concern. In the last week alone, 45 new domestically acquired cases were diagnosed or reported, a figure that accounts for a significant share of all cases recorded since the start of this year’s transmission season. Nine deaths - sixteen patients in ICUs The seriousness of the current situation is also reflected in patients’ condition. By 12 August, nine deaths had been recorded among patients with West Nile virus infection and CNS manifestations. All those who died were over 65 years of age, with a median age of 82 and an age range from 66 to 91 years. At the same time, 35 patients were still in hospital. Of these, 19 were in ordinary hospital wards and 16 in Intensive Care Units, while none were in a High Dependency Unit. In total, 61 patients had been discharged, while five of the recorded cases did not need hospitalisation. Age appears to be a key characteristic of the more serious cases. The median age of patients with CNS manifestations is 73 years, although cases span a much wider age range, from 19 to 91 years. The true extent of infections may be much greater The 110 laboratory-confirmed domestically acquired cases do not necessarily reflect the total number of people who have been infected. EODY recalls that, according to the results of a 2010 seroepidemiological study, for every single case of West Nile virus infection with CNS involvement there are around 140 infected people, who either develop mild symptoms or remain asymptomatic. This is an important caveat when interpreting the official figures: the recorded severe cases represent only part of the virus’s overall circulation in the population. Attica at the epicentre of this year’s circulation The geographical pattern is particularly noteworthy, as Attica is at the epicentre of this year’s viral activity. By 12 August, cases had been recorded and investigated in 39 municipalities, in 14 regional units and in four regions: Attica, Thessaly, Central Macedonia and the Peloponnese. In Attica, areas in East Attica and the North, West, Central and South Sectors of Athens, as well as Piraeus, have been affected. Outside Attica, cases have been recorded in the regional units of Karditsa, Larissa, Trikala, Imathia, Thessaloniki, Pella, Serres and Laconia. EODY itself notes that in the Region of Attica in particular, there is especially intense circulation of the virus this year, with increased numbers of cases in specific areas and regional units. Spata-Artemida and Markopoulo among the areas with a higher burden East Attica appears particularly hard-hit. In the municipality of Spata-Artemida, 11 patients with CNS manifestations and two without such manifestations have been recorded. In the municipality of Markopoulo Mesogaias, eight patients with CNS involvement and three without have been reported, while in the municipality of Vari-Voula-Vouliagmeni there have been five cases with CNS manifestations and two without. In Pallini there are five cases with CNS involvement, in Agia Paraskevi six, in Acharnes three, in Chalandri three, in Glyfada three and in the municipality of Athens three. The proportion of severe cases is particularly high in certain municipalities in East Attica. In Markopoulo Mesogaias there are 36.8 cases with CNS manifestations per 100 000 inhabitants, while in Spata-Artemida the rate stands at 31.5 per 100 000 inhabitants. ‘High-risk’ municipalities with no human cases yet The focus of the health authorities is not limited to areas where human cases have already been recorded. On the basis of an assessment of epidemiological and geomorphological data, additional municipalities have been classified as ‘high-risk areas’: Kifisia, Iraklio, Filothei-Psychiko and Metamorfosi in the North Sector of Athens, Kallithea and Nea Smyrni in the South Sector, Nea Filadelfeia-Nea Chalkidona and Dafni-Ymittos in the Central Sector, as well as the municipalities of Amfipoli in Serres, Heroic City of Naousa in Imathia and Delta in the Metropolitan Unit of Thessaloniki. In these municipalities, no human cases had been recorded by the time the report was published. Their classification as high risk stems from factors such as proximity to already affected municipalities, geomorphological characteristics and current and historical epidemiological data. The virus is also being detected in equines Veterinary surveillance also provides an indication of the wider geographical circulation of the virus. By 12 August, recent West Nile virus infections in equines had been recorded in a total of five sites or settlements, in the regional units of East Attica, Drama and Preveza, as well as in the Metropolitan Unit of Thessaloniki. As the report emphasises, the detection of a recent infection in equines indicates circulation of the virus in those areas as well. Enhanced surveillance and investigation of every case within 24 hours The response to the situation is based on an enhanced epidemiological surveillance system, which EODY has been implementing continuously since 2010. Every reported case is investigated within 24 hours, through contact with the treating doctors and an interview with the patient. The aim is to determine the probable place of exposure, risk factors and disease severity. For hospitalised patients, the clinical course and final outcome are monitored daily. There is also daily communication with laboratories carrying out tests for the virus, while support is provided for the laboratory investigation of suspected cases and for the operation of specialised laboratories. EODY has issued specific guidance to health professionals on the need for timely identification and investigation of suspected cases. In May 2026, an information letter was sent to all health facilities and medical associations in the country, while when cases appear in specific areas, local health units receive additional urgent briefings. Similarly, the regions, municipalities, public health directorates, the Ministry of Health, the Ministry of Rural Development and Food and the National Blood Centre are informed about diagnosed cases and the recommended response measures. Particular attention is paid to blood safety. An intersectoral working group assesses epidemiological, entomological, geomorphological and other available data and defines the ‘affected’ areas and the ‘high-risk’ areas. In these areas, the necessary measures for blood safety are implemented by the National Blood Centre, while the relevant guidance for the country’s blood services is decided and circulated by the National Center for Blood Donation (EKEA). Mosquito-control programmes stepped up Integrated mosquito management plays a central role in prevention and is the responsibility of local authorities. In March 2026, the Ministry of Health issued a specific circular on integrated mosquito management programmes, while the national action plan provides for different interventions depending on each area’s level of risk. EODY has asked regions and municipalities for the timely launch, proper organisation and effective implementation of mosquito-control programmes. When new cases occur, local authorities receive urgent briefings and are advised, among other things, to step up mosquito-control operations and strengthen public information at local level. At the same time, the progress of mosquito-control projects is monitored by region or regional unit. Mosquito traps as an early-warning system Entomological surveillance is a key component of the strategy. EODY, in cooperation with other bodies, installs mosquito traps in different parts of Greece. The mosquitoes collected are tested for the presence of West Nile virus, creating in effect an early-warning system before or in parallel with the appearance of human cases. When there are indications of virus circulation in mosquitoes, the competent regional authorities are immediately informed so that targeted control measures can be implemented. EODY also recommends intensifying entomological surveillance in the wider affected areas. For 2026, an enhanced entomological surveillance network has been set up, with a representative geographical spread of sampling sites and cooperation between universities, research institutes and public bodies. The virus is now established in Greece - further cases expected The presence of West Nile virus is not being treated as a one-off phenomenon confined to this summer. According to EODY, cases have been recorded in Greece during the periods from 2010 to 2014 and from 2017 to 2025, mainly in the summer and autumn months. In the past, circulation of the virus has been documented in all regions of the country. The almost annual occurrence of cases since 2010 indicates, according to the report, that West Nile virus has become established in Greece, as it has in other European countries. EODY’s message for the coming weeks is clear: the diagnosis of additional cases is considered likely, both in areas where the virus is already circulating and potentially in new areas. The geographical spread cannot be predicted with confidence, as the virus’s epidemiology is influenced by many different factors. For this reason, the protection advice does not apply only to residents of Attica or to municipalities where cases have already been recorded. In its conclusions, EODY identifies three main pillars as the most appropriate measures for controlling the infection: epidemiological surveillance, timely implementation of suitable integrated mosquito-control programmes and individual protection against mosquitoes. At the same time, ongoing vigilance is deemed essential, both among health professionals and among local and national authorities.