Greece is once again among the European countries experiencing a significant burden from West Nile virus, with the National Public Health Organization (EODY) estimating that the current transmission season could turn out to be one of the most difficult in recent years in terms of the number of cases recorded.

The intense circulation of the virus, particularly in areas of Attica, and the rapid increase in cases from the early stages of the transmission season have put health authorities on heightened alert. At the same time, EODY makes clear that there is currently no scientific evidence that the virus has changed its behavior or is more transmissible compared with previous periods.

The picture this year is attributed to a complex combination of factors affecting mosquito populations. Increased temperatures and rainfall are the parameters most strongly associated with seasonal outbreaks of the virus, Danae Pervanidou, MD, MPH, head of the Department of Vector-Borne Diseases at the Directorate for Epidemiological Surveillance and Prevention of Infectious Diseases of the National Public Health Organization (EODY), said in an interview with the Athens-Macedonian News Agency (ANA-MPA).

“For example, the warm winter of 2025-2026 in Attica (the second-warmest of the past 150 years) may have contributed to the current epidemiological picture,” she said.

The following is the text of Ms. Pervanidou’s interview with ANA-MPA:

Q: What is the current epidemiological picture of West Nile virus in Greece?

A: In our country, as in other European countries, cases of West Nile virus infection have been recorded every year since 2010, almost annually, during each mosquito circulation season. Therefore, it is estimated that West Nile virus has become established in our country as well, and the reappearance of cases during each transmission season is considered expected.

EODY had already informed healthcare professionals nationwide in May 2026 of the need to remain vigilant for the timely diagnosis of cases, as well as the public regarding the expected reappearance of cases in the country during the current mosquito circulation season and the recommended protective measures.

During the 2026 season, up to August 12, a total of 110 cases of the infection have been recorded in Greece, of which 81 presented with manifestations involving the Central Nervous System and 29 had mild symptoms. The cases were recorded in 39 municipalities across the country, in 14 Regional Units, in the regions of Attica, Thessaly, Central Macedonia and the Peloponnese.

Further cases are expected to be diagnosed in the coming period, both in the same areas and in new areas, which cannot be safely predicted. In the Attica Region in particular, there is particularly intense circulation of the virus this year, with an increased number of cases in specific areas/Regional Units.

Q: Greece is among the European countries with the highest number of cases. How does EODY assess this year’s outbreak?

A: Regarding West Nile virus infection, at the European level, Greece is among the countries most affected every year in terms of the number of cases and disease incidence (per 100,000 population), usually alongside Italy and, at times, other countries, mainly in central Europe and the Balkans.

Of course, epidemiological surveillance of the infection is particularly strengthened in our country, and doctors in Greece are sufficiently sensitized and vigilant regarding the diagnosis of cases, so we estimate that a large proportion of at least the severe cases are diagnosed. In addition, through the active laboratory surveillance system in place, all diagnosed cases are reported daily to EODY, meaning that for this particular disease we do not have underreporting (all diagnosed cases are reported and recorded).

It is a fact that during the current transmission season, there is particularly intense circulation of the virus, especially in areas of Attica, with the number of cases so far exceeding the number of cases recorded in previous years during the corresponding period, with a rapidly increasing number of cases in specific areas. The causes determining the intensity of the seasonal outbreak of the infection during each transmission season are complex and multifactorial.

Q: Is there any indication that the virus is behaving differently or is more transmissible than in previous periods, or is the increase mainly attributed to environmental conditions?

A: There is currently no scientific evidence of a different transmissibility or behavior of the virus. It is known that the epidemiology of the virus is complex and determined by many factors that influence the intensity of its circulation and transmission, such as the migratory routes of birds (which are the main reservoir of the virus in nature and “introduce” the virus into an area), the populations, diversity and immunity of wild bird reservoir populations (migratory and local), mosquito vector populations, and environmental and climatic parameters. This is why we cannot easily predict either the intensity of the virus’s circulation or its geographical distribution during each transmission season.

Meteorological and climatic parameters affect both mosquito populations and the ability of mosquitoes to acquire, maintain and transmit the virus, and consequently the proportion of infected mosquitoes circulating and the intensity of virus circulation. Increased temperatures and rainfall are the parameters most strongly associated with seasonal outbreaks of the virus. For example, the warm winter of 2025-2026 in Attica (the second-warmest of the past 150 years) may have contributed to the current epidemiological picture.

Q: How concerned is EODY about the increased circulation of the virus in Attica, given its large population and population density?

A: The increased rate of recorded cases this year, relatively early in the current transmission season, particularly in areas of Attica, indicates a risk of continued recording of a particularly high number of cases in the coming weeks, as a result of the intense circulation of the virus among mosquitoes in areas with high population density. If the same rate of case reporting continues, this year’s season is expected to be one of the most difficult in terms of the number of cases that will be recorded. This is why vigilance and rapid response from the competent local authorities are needed for the immediate implementation of the recommended response measures at the local level, as well as public awareness regarding the meticulous adoption of personal mosquito protection measures.

Q: When is this year’s transmission season expected to peak?

A: Based on historical data, the peak of the seasonal outbreak of the infection usually occurs during the second half of August, from mid-to-late August through early-to-mid September.

Q: What does EODY’s planning provide for the coming weeks, and what additional measures could be taken if the upward trend continues?

A: The epidemiological surveillance carried out by EODY is among the most comprehensive in Europe. All diagnosed cases are immediately reported to EODY directly by cooperating laboratories, and EODY investigates cases within 24-48 hours of their diagnosis and immediately informs the authorities that need to take action. It immediately informs municipalities and regions about cases and, on a regular basis, about the Risk Level of each municipality. There is a national Action Plan that describes the recommended prevention and response measures for each Risk Level. In addition, EODY immediately informs local health units about virus circulation at the local level. It informs healthcare and public health professionals and the public through weekly reports and press releases when deemed appropriate. This year, three press releases have already been issued regarding West Nile virus infection. Surveillance and response by national public health authorities are already operating at the highest level.

The “additional measures” that need to be taken are described in detail in the Action Plan and mainly concern the continued, systematic and emergency response of local government authorities, to intensify mosquito management activities and public information campaigns (on personal protection measures and the elimination of mosquito breeding sites in private spaces).

Q: What is EODY’s message to citizens?

A: First of all, citizens should consistently follow personal mosquito protection measures, that is, avoid mosquito bites as much as possible. This does not mean that all mosquitoes are infected—most are not. However, because some mosquitoes are infected in certain areas, citizens should take precautions.

They should use approved insect repellents for the body and living spaces (e.g. tablets, mosquito coils), according to the instructions for use; use screens, mosquito nets, air conditioners/fans; and wear long clothing, especially from dusk onward (as far as the weather permits).

They should monitor and stay informed about areas where the virus is definitely circulating, that is, areas where cases have been recorded, and if they live in or visit these areas, they should be particularly careful.

Older people, people with immunosuppression (e.g. lymphoma, leukemia, other malignancies, autoimmune diseases, transplant recipients, those taking immunosuppressive medications), or other chronic underlying conditions should follow mosquito protection measures particularly consistently, as they are at greater risk of developing severe illness. Age is the most important risk factor for severe disease and—even fatal—complications, and people with immunosuppression are also at serious risk.

At the same time, an important preventive measure is the removal/elimination of stagnant water sites where mosquitoes lay their eggs, in order to limit breeding sites in private spaces. Community participation is crucial in reducing these sites, as the competent local authorities cannot intervene in private spaces. In practice, all private spaces (yards, gardens, verandas, rooftops, balconies, fields, plots of land) should be regularly and thoroughly checked for stagnant water sites and these should be eliminated. All objects that may collect water should be turned upside down or covered, or their water should be replaced at least once a week. Gutters, drains and channels should be cleaned, and ventilation pipes or other open passages of septic tanks should be covered with screens.

In conclusion, it is important to recognize the role of mosquitoes as vectors of disease and to take appropriate preventive measures. There is no need for concern, but it is important to stay informed, vigilant and consistent in implementing protective measures.