Greece has recorded a worrying rise in West Nile virus infections, prompting concern given that the mosquitoes which transmit the virus bite people repeatedly throughout the season. In response to the surge, health authorities have stepped up mosquito control measures nationwide.

Eastern Attica is the worst-affected part of the country, according to data published by EODY, the National Public Health Organisation. Cases have so far been recorded in the regions of Attica, Thessaly, Central Macedonia, the Peloponnese and Central Greece, with Attica seeing far more infections this transmission season than in previous years.

The highest concentrations have been recorded in the municipality of Spata-Artemida (Loutsa), with 14 cases, followed by Markopoulo Mesogaias with 11 and Vari-Voula-Vouliagmeni with 9. Agia Paraskevi has recorded 6 cases, Pallini and Chalandri 5 each, and Glyfada 4.

Authorities remain on alert, with daily spraying under way in the municipalities recording the highest numbers of serious cases involving the central nervous system (CNS).

Experts say around 80% of people infected with the virus show no symptoms at all. About 20% develop mild symptoms such as fever, headache and muscle pain, while roughly 1% of those infected may go on to develop serious neurological complications, including encephalitis and meningitis.

Symptoms such as confusion, fainting, seizures and paralysis require immediate medical assessment, and anyone who develops them should be taken to hospital straight away. Scientists stress that West Nile virus is not transmitted from person to person, but exclusively through the bite of an infected mosquito.

Weekly EODY surveillance report

According to EODY’s latest weekly epidemiological surveillance report, 157 domestically acquired cases of West Nile virus infection had been diagnosed and reported in Greece from the start of the 2026 season up to 19 August (11am). Of these, 116 involved CNS effects (encephalitis and/or meningitis and/or acute flaccid paralysis), while 41 had mild or no CNS symptoms.

A further 47 new domestic cases were diagnosed or reported in the past week alone. One additional case, involving a complex travel history that included a stay in a country where the virus is endemic, has not been included in the analysis, as the likely country of exposure could not be determined.

In total, 13 deaths have been recorded in 2026 up to 19 August among patients with CNS-related infection, all of them aged over 65. The median age of those who died was 82, with ages ranging from 66 to 91.

The report also sets out the current hospitalisation status of domestic cases as of 19 August, and includes a chart showing the weekly distribution of domestic CNS cases by week of symptom onset, comparing 2026 with the previous three years (2023 to 2025) and with 2018, which recorded the highest annual number of cases on record. The first case of the 2026 season had its onset of symptoms on 25 June (week 26).

Guidance from EODY

EODY has issued advice urging the public to protect themselves against mosquitoes:

• Use approved body and area insect repellents as directed, along with window screens, mosquito nets, air conditioning or fans, and suitable long clothing.
• Do not leave standing water anywhere. Regularly check gardens, yards, verandas, terraces, balconies, fields and plots of land for pools of stagnant water and eliminate them.
• Turn over, cover or empty and refresh the water in any object that collects rainwater at least once a week.
• Cover the ventilation pipes of septic tanks with mesh.

When symptoms start

Scientists say that, when symptoms do develop, they usually appear 2 to 6 days after being bitten by an infected mosquito, though onset can be delayed by up to 14 days in less common cases. In people with weakened immune systems, symptoms may take even longer to appear. Even so, around 80% of those infected with West Nile virus never develop any symptoms.

How mild illness presents

Of the remaining cases, just under 20% experience flu-like symptoms, including:

• Fever with headache
• Muscle aches
• Joint pain
• Fatigue
• Weakness

Patients may also experience gastrointestinal symptoms such as vomiting or diarrhoea, along with a temporary skin rash. Most people with mild illness recover fully, though fatigue and weakness can persist for weeks or months.

What symptoms severe illness causes

Fewer than 1% of people infected with West Nile virus go on to develop severe illness. This is known as neuroinvasive disease, because it affects the central nervous system, made up of the brain and spinal cord.

When the virus causes neuroinvasive disease, it can present as encephalitis, meningitis or similar conditions. Encephalitis refers to inflammation of the brain, while meningitis refers to inflammation of the meninges, the protective membranes surrounding the brain and spinal cord.

Symptoms

• High fever
• Severe headache
• Neck stiffness
• Lethargy
• Disorientation
• Tremor
• Seizures
• Muscle weakness
• Loss of vision
• Numbness
• Paralysis

Patients may fall into a coma, and severe illness always requires hospital treatment. Recovery can take several weeks or months, and sometimes leaves permanent neurological damage. In around 10% of cases, the neuroinvasive form of the disease proves fatal.

When to see a doctor

The US Centers for Disease Control and Prevention (CDC) advises seeking immediate medical attention if you are bitten by mosquitoes and, a few days later, develop a high fever, neck stiffness, muscle weakness, mental confusion or tremor. The risk of serious illness is three times higher in people over 65.