By Ana Espino | Published on June 25, 2026 | 4 min read
West Nile virus (WNV) is an arbovirus transmitted primarily
by mosquitoes of the Culex genus. First identified in Uganda in 1937, it
is now present across multiple continents and has become one of the leading
causes of mosquito-borne viral encephalitis. Once considered a sporadic
infection, WNV has evolved over recent decades into a growing public health
threat in Europe, North America, and parts of Asia and the Middle East.
In a recent review examining the epidemiology, surveillance,
and prevention strategies related to West Nile virus, the authors analyze the
mechanisms driving its global spread, as well as recent advances in
understanding its biology and control. Their synthesis highlights, in
particular, the increasing influence of climate change on the virus’s
transmission dynamics.
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Nile: the fever is rising!
A Transmission Cycle Facilitated by Environmental Changes
The virus naturally circulates between wild birds,
which serve as its primary reservoir, and Culex mosquitoes, the main
vectors responsible for transmission. Humans and horses are considered
incidental or “dead-end” hosts, as they generally do not develop sufficient
levels of virus in their bloodstream to sustain further transmission.
Authors emphasize that rising temperatures, changing
precipitation patterns, and the geographic expansion of mosquito populations
are increasingly facilitating viral circulation in regions that were previously
only minimally affected. Several recent studies have demonstrated a correlation
between favorable climatic conditions and the emergence of epidemic outbreaks
in Europe.
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Zoonotic Viruses: Is Climate Change Setting the Stage for Future Epidemics?
An Infection That Is Often Silent but Sometimes Severe
Most human infections remain asymptomatic. However,
approximately 20% of infected individuals develop a febrile illness
characterized by fatigue, headache, muscle pain, and skin rash.
In fewer than 1% of cases, the infection progresses
to a severe neuroinvasive disease, leading to encephalitis, meningitis,
or acute flaccid paralysis.
These complications occur particularly among older adults
and immunocompromised individuals. Some neurological sequelae may persist long
after the acute phase of infection, highlighting the importance of early
diagnosis and careful clinical monitoring.
A lire également : Déterminants
de l’encéphalite provoquée par le virus West Nile
A Concerning Increase in Europe
The review highlights the recent rise in human cases across
several European countries. Italy has emerged as one of the main
hotspots of viral circulation on the continent. Recent studies have documented
the rapid spread of new viral lineages associated with an increased risk of
neuroinvasive disease during outbreaks observed in recent years.
Authors also stress that integrated surveillance of human,
animal, and entomological populations is becoming essential for the early
detection of viral circulation and the anticipation of epidemic outbreaks.
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Making a Comeback? The Trap of Imported Cases
Promising Vaccines but Limited Availability for Humans
Although several vaccines are already used successfully in
horses, no widely available vaccine currently exists for the general human
population. Research is ongoing using a variety of vaccine platforms,
including inactivated vaccines, recombinant vaccines, and viral vector-based
vaccines. Several recent candidates have demonstrated encouraging results
in preclinical studies.
At the same time, multiple therapeutic strategies targeting
viral proteins involved in replication are under development, although no
specific antiviral treatment has yet demonstrated sufficient clinical efficacy.
A “One Health” Approach Has Become Essential
Given the expanding geographic range of West Nile virus, the
authors conclude that controlling this arboviral disease requires an integrated
One Health approach combining human, veterinary, and environmental
surveillance.
Strengthening mosquito and bird monitoring programs,
improving early warning systems, and accelerating the development of human
vaccines are considered major priorities for reducing the future impact of this
emerging disease.
In a context marked by climate change and increasing
interactions between humans, animals, and disease vectors, West Nile virus is
now regarded as one of the most emblematic examples of the public health
challenges posed by emerging vector-borne diseases.
About the author – Ana Espino
PhD in Immunology, specialized in Virology
As a scientific writer, Ana is passionate about bridging the gap between research and real-world impact. With expertise in immunology, virology, oncology, and clinical studies, she makes complex science clear and accessible. Her mission: to accelerate knowledge sharing and empower evidence-based decisions. 
