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Written by Professor Emeritus of the Aristotle University of Thessaloniki, Pavlos Nikolaidis, Pathologist – Infectious Diseases Specialist, Director of the Pathology-Infectious Diseases Department of the Inter-Balkan Medical Center of Thessaloniki

Summer may have ended in terms of the calendar, but the period of transmission of the West Nile virus does not necessarily end with it. Mosquitoes are still active in the first autumn months, especially when temperatures remain high. For this reason, protection from bites remains important in September, but also as long as mosquito circulation continues.

This year’s epidemiological picture in our country confirms the need for increased caution. According to the most recent available data from the National Public Health Organization, as of September 9, 2026, 324 domestic cases of West Nile virus infection had been recorded, while 217 of them presented with manifestations from the Central Nervous System, such as encephalitis, meningitis or acute flaccid paralysis. During the same period, 30 deaths had been recorded, all in patients over 65 years of age.

These data do not mean that fear should be created in the population. However, they do mean that caution and simple preventive measures need to be continued.

How is the virus transmitted

West Nile virus is transmitted mainly through the bite of infected mosquitoes. In nature, mosquitoes are mainly infected when they feed on infected birds and can then transmit the virus to humans. Humans are not a source for the continuation of the mosquito-borne transmission cycle.

In the vast majority of cases, the infection either causes no symptoms or manifests itself with mild symptoms. According to the National Institute of Public Health, approximately 80% of people who are infected remain asymptomatic, while approximately 20% experience mild disease, with fever, headache, fatigue, myalgia or arthralgia and, in some cases, gastrointestinal symptoms or rash.

In less than 1% of infections, severe disease with involvement of the Central Nervous System may occur. The likelihood of severe disease is greater in older people, as well as in people with immunosuppression or chronic underlying diseases.

Why we shouldn’t relax measures because autumn has arrived

The arrival of autumn does not mean that mosquito activity automatically stops. The transmission of the virus is linked to the presence and activity of mosquitoes and not to the date on the calendar.

The National Organization for Public Health points out that cases usually peak from mid-August to early September, while the areas in which the virus will circulate in the coming weeks cannot be predicted with certainty. For this reason, it recommends the continuation of individual protection measures throughout the territory and throughout the mosquito circulation period.

Therefore, there is no specific date on which we can say that the need for protection “ends”. The measures must continue as long as mosquitoes exist and weather conditions allow their activity.

What are the basic self-protection measures

Prevention remains our most important weapon. The measures are simple and can be easily incorporated into our daily lives:

• We use approved body insect repellents, according to the instructions for use.
• We wear, especially outdoors, appropriate and as long as possible clothing that covers arms and legs.
• We use screens on doors and windows and, where necessary, mosquito nets.
• We use air conditioners or fans, as air movement makes it difficult for mosquitoes.
• We avoid the presence of stagnant water around the house.
• We turn over or cover objects that can hold water, while in containers that cannot be emptied, we ensure frequent renewal of the water.
• We systematically check balconies, yards, gardens, terraces and other areas around the home.

Particular consistency is needed by older people, people with chronic diseases and those who are immunosuppressed, as these groups are at increased risk of serious illness.

When to contact a doctor

A mosquito bite, in itself, does not mean that someone is infected with West Nile virus. However, when symptoms such as fever, severe headache and significant fatigue appear after exposure to mosquitoes, especially in older people or people with a complicated medical history, it is advisable to contact the treating doctor.

Particular attention is required when symptoms from the nervous system appear, such as neck stiffness, confusion or impaired level of consciousness, unsteadiness in walking, seizures or severe muscle weakness, as these may be associated with a severe form of the infection and require immediate medical evaluation.

Protection does not end with summer

West Nile virus is now a disease that re-emerges in our country during the summer and autumn months. Its presence cannot be predicted with absolute accuracy from region to region, which is why personal protection is important regardless of whether cases have been reported in our neighborhood.

The message is simple: autumn does not mean that we stop being careful. We continue to protect ourselves from mosquitoes as long as they remain active. These are simple daily habits that can significantly reduce the risk of exposure and are particularly important for our most vulnerable fellow citizens.