WHO warns of rising West Nile virus as warming expands mosquito season
Rising West Nile virus infections across southern Europe highlight the mounting public health burden driven by longer, warmer summers.
Health authorities across southern Europe are reporting a sharp rise in West Nile virus cases as the peak transmission season begins. The season typically runs from late spring to autumn, peaking between July and September. Greece has recorded 21 confirmed human infections as of 22 July.
Twenty of those Greek patients developed severe neuroinvasive disease, such as encephalitis or meningitis, and 13 currently remain in hospital. Italy has documented a similarly broad geographic spread, with 21 confirmed cases distributed across 17 separate areas as of 15 July.
Locally acquired infections have also been identified in Spain, Romania and North Macedonia, with each country reporting two cases. The concentration of severe, hospital-bound infections underscores the tangible strain the virus places on regional healthcare systems during the summer months.
The World Health Organization connects this expanding territorial spread directly to shifting climate patterns. “West Nile virus is not a new threat, but the conditions driving its spread are changing rapidly,” said Hans Henri P. Kluge, WHO Regional Director for Europe.
“Warmer temperatures and longer summers are giving mosquitoes more time and territory to transmit this virus.” This climate-driven expansion represents a growing, long-term challenge for European public health infrastructure.
With no licensed human vaccine available, medical treatment remains limited to symptom management and supportive hospital care. To curb transmission, the WHO is advising residents in affected regions to adopt immediate preventive measures.
“Simple steps like covering up, using insect repellent and clearing stagnant water around the home can make a real difference,” Kluge said on Friday. The agency recommends limiting outdoor exposure at dawn and dusk, installing window screens and using mosquito nets.
Eliminating standing water in pots and waste containers is also crucial to destroy mosquito breeding sites. While roughly 80% of infected people show no symptoms, others experience fever, fatigue, muscle aches or nausea.
“Anyone who develops a high fever, rash or neck stiffness after a mosquito bite should see a doctor without delay,” Kluge warned. He noted that around one in 150 infections results in life-threatening central nervous system disease.
