West Nile virus activity in the 2026 season has accelerated sharply on both sides of the Atlantic, with the United States recording 48 human cases by the end of June — 38 of them neuroinvasive — a level federal and local health officials describe as well above average for this point in the year. In Italy, where the virus is endemic across the Po basin and beyond, six regions had reported hospitalisations by mid-July, following a 2025 season that caused more than 500 confirmed infections and over 30 deaths. The European Centre for Disease Prevention and Control flagged the pathogen as a growing public-health concern on 7 July, noting that local transmission is now occurring with greater frequency in parts of Europe where the Culex mosquito vector is established.

The most severe presentation, West Nile virus encephalitis, has already been documented. Los Angeles County confirmed its first case of 2026 in an Antelope Valley resident hospitalised with the rare neurological complication, which occurs in fewer than one per cent of infected individuals. In Emilia-Romagna, an 80-year-old man from the Modena area became the region’s first confirmed patient of the summer and remains in stable condition. Italian surveillance systems also detected a mild case in a 29-year-old in Latina province, Lazio, and a cluster of three patients in Novara, Piedmont, two of whom remain hospitalised with neurological symptoms. Earlier cases were recorded in Sardinia, Campania, Tuscany and Veneto, indicating wide geographic circulation.

Health authorities on both continents stress that the virus is maintained in a bird-mosquito cycle, with humans and horses serving as dead-end hosts incapable of further transmission. The Culex mosquito, active primarily at dusk and at night, is the principal vector. No vaccine or specific antiviral treatment exists. Public-health responses therefore centre on prevention: use of repellents containing DEET or Picaridin, removal of standing water, and reporting of dead birds, which can signal rising viral activity before human cases appear. In Italy, regional health agencies note that disinfestation around patients’ residences is not required because the virus is not transmissible between people, a protocol that differs from the response to imported arboviruses such as Dengue.

Surveillance networks in both countries have been strengthened after the 2025 season, which saw Italy account for more than 80 per cent of the 335 West Nile infections reported across eight EU member states. The early-season case count in 2026 suggests the virus is circulating earlier and more widely, though officials caution that most infections remain asymptomatic and that detection of mild cases reflects improved clinical awareness and diagnostic capacity. The next factual milestone is the peak transmission window in August and September, when mosquito abundance typically reaches its maximum and the true scale of this year’s outbreak will become clearer.