Professor of Hygiene and Epidemiology at the National and Kapodistrian University of Athens (EKPA), Gkikas Mayorkinis, sought to reassure the public regarding the increased number of West Nile virus cases recorded in Attica, with the outbreak concentrated mainly in areas such as Markopoulo and Spata.

Speaking on Thursday morning (August 20) on ERT, Mr. Mayorkinis discussed the current situation compared with the same period in 2025 and explained what may be behind the increase in cases.

He stressed that the majority of people who become infected do not even realize they have contracted the virus, since in most cases the infection passes without significant symptoms. Involvement of the central nervous system, he said, occurs in approximately one in every 150 infected people.

When the infection becomes severe, the clinical picture can be serious and may require hospitalization. High fever, severe headache, lethargy, photophobia, seizures, or paralysis may indicate involvement of the central nervous system and therefore require immediate medical evaluation.

There is no specific treatment for West Nile virus. Treatment is supportive and is tailored to each patient’s condition and needs.

The professor also noted that severe cases are the ones that require specialized diagnostic testing. At the same time, the interval between being bitten by an infected mosquito and developing symptoms varies from person to person. In some cases, symptoms may appear as much as two weeks later.

What does a mosquito bite look like, and why are cases increasing?

Mr. Mayorkinis also clarified that there is no specific skin reaction that can tell someone whether the mosquito that bit them was infected with West Nile virus.

A mark or reaction on the skin is caused by the mosquito’s saliva and the allergic response it may trigger in the body, rather than by the presence of the virus.

According to the latest data from the National Public Health Organization (EODY), during the most recent week, through August 19, 2026, 47 new locally acquired cases of West Nile virus infection were diagnosed and reported. One additional case involved a complex travel history, including travel to an endemic country abroad. Since the beginning of 2026, the total number of cases has reached 157, with 13 deaths recorded.

Regarding the reason for this year’s increase, the epidemiology professor said it cannot be determined with certainty. He explained, however, how the virus circulates in nature: mosquitoes become infected by biting birds carrying the virus, particularly corvids such as crows, magpies, and jackdaws.

The increased concentration of cases in particular geographical areas, according to Mr. Mayorkinis, indicates that there may be populations of infected birds in those areas.

Among the possible explanations he mentioned is a scenario involving the movement of birds following Storm Daniel in 2023, when Thessaly was an area of significant virus activity.

The professor also emphasized the importance of mapping cases geographically. Reporting the locations where cases occur is particularly useful because mosquitoes cannot travel very long distances.

More areas are being affected by the virus

Five new municipalities in Greece were affected by West Nile virus during the past week. These are municipalities where residents were exposed to the virus for the first time in recent days.

Of these newly affected areas, three are in Attica: Dionysos, Petroupoli, and Kallithea. The other two are in Imathia (Alexandria Municipality) and Central Greece (Thebes Municipality).

According to an EODY report, a total of 45 municipalities nationwide — including 29 in Attica — have been affected by West Nile virus and are considered areas where patients have been exposed to the virus.

Nine municipalities — Kifisia, Iraklio, Filothei-Psychiko, Metamorfosi, Nea Smyrni, Dafni-Ymittos, Nea Filadelfeia-Nea Chalkidona in Attica, Amphipoli in Serres, and Heroic City of Naousa in Imathia — have not recorded a human case but have been classified as high-risk areas by the relevant working group.

The designation is based on a combination of risk factors, including proximity to affected areas, geographical characteristics, current and historical epidemiological data, and available surveillance data on virus circulation among mosquitoes and animals in the wider area.

It is worth noting that in the recent past, areas classified as high-risk have quickly become affected areas.

An important factor is that the overwhelming majority of people infected with the virus are asymptomatic, while only a very small percentage develop symptoms involving the central nervous system. One study found that for every one case of West Nile virus infection involving the central nervous system, there are approximately 140 infected people who are asymptomatic or have mild symptoms, such as sudden fever, severe headache, muscle and joint pain, fatigue and weakness, skin rash, and nausea, vomiting, or diarrhea.

People over the age of 50, immunocompromised individuals, and people with underlying medical conditions face the greatest risk of developing severe illness and should therefore follow protective measures particularly carefully.