#WestNile #Mosquito #Epidemiology #ZoonosisWest Nile Virus (WNV), an arbovirus transmitted by mosquitoes and
primarily hosted by birds, represents a major public health concern in the
Mediterranean region. This zoonotic disease can cause clinical manifestations
ranging from mild symptoms to
severe encephalitis, especially in the elderly or
immunocompromised individuals.
Despite the existence of surveillance systems in many Mediterranean
countries,
control measures remain limited due to the lack of a human vaccine
and curative treatment. Prevention relies mainly on
vector control and
early
detection of outbreaks. One of the main challenges lies in
the silent
circulation of the virus in endemic areas, facilitated by climate change, avian
migratory flows, and the diversity of mosquito vectors. Additionally,
disparities in surveillance strategies between countries make epidemic
forecasting difficult.
This study aims to
provide an updated overview of WNV epidemiology in
the Mediterranean Basin from 2010 to 2023 by analyzing spatiotemporal trends,
host species, circulating viral lineages, and the effectiveness of surveillance
systems.
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West nile: where, when, and why is it surging?
The study is based on the analysis of data collected from 20
Mediterranean countries between 2010 and 2023. It draws on national
epidemiological reports, notifications to the ECDC and OIE, and scientific
publications. Human and animal cases (mainly equine), as well as environmental
detections (mosquitoes, birds), were included, with special focus on viral
lineages (WNV-1 and WNV-2) identified through sequencing.
The study reveals a
general increase in human and animal cases during
the study period, with a
major peak in 2018. The most affected countries
include Italy, Greece, Serbia, Tunisia, and Turkey. The virus circulates
primarily between June and October, with a progressive geographic expansion
toward the north.
Two viral lineages predominate: WNV-1, historically the most common, and
WNV-2, responsible for an epidemic resurgence since 2010.
Transmission is
strongly influenced by climatic conditions, especially high summer temperatures
and spring rainfall. The data also show an
increase in early detections in
mosquitoes and birds, reflecting
improved integrated surveillance systems (a
"One Health" approach).
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A well-established virus, a future to monitor
West Nile virus remains a
priority pathogen in the Mediterranean Basin
due to its
endemic presence, epidemic potential, and
the absence of specific
treatment. Surveillance is especially critical for anticipating seasonal
outbreaks. Key challenges include the
heterogeneity of surveillance systems,
lack of standardized data across countries, and
the difficulty of predicting
epidemics based on ecological conditions. This study aimed to consolidate
regional epidemiological knowledge to better target interventions.
The results highlight the
need for an integrated approach that combines
human, animal, and entomological surveillance to enable early detection and
effective epidemic risk management. However, the analysis remains hampered by
disparities in surveillance systems, lack of common indicators, and incomplete
data availability. To strengthen the fight against West Nile virus,
several
strategies should be considered: harmonizing epidemiological monitoring
strategies at the regional level, integrating climate modeling into forecasting
tools, accelerating the development of human vaccines, and establishing
coordinated prevention programs between countries. WNV thus emerges as a
sensitive indicator of increasing tensions between human health, environmental
factors, and climate dynamics.
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