Title : An unprecedented West Nile virus outbreak in Israel (2024): A textbook case for the One Health approach
Abstract:
Background: West Nile Virus (WNV) is a well-established flavivirus endemic to Israel, maintained in an enzootic cycle between Culex spp. mosquitoes and avian reservoirs, with humans and equines serving as incidental "dead-end" hosts. While approximately 80% of human infections remain asymptomatic, the virus can cause severe neurological illness and fatalities. In June 2024, central Israel experienced an unprecedented surge in WNV activity, presenting significant deviations from historical baselines in morbidity, mortality, and positivity rates in both humans and birds, in addition to WNV infected mosquitoes’ diagnosis.
Methods & Inter-Sectoral Surveillance: A synchronized, multi-agency "One Health" investigation was launched involving public health, environmental, and veterinary sectors. The Ministry of Health monitored human clinical data. Concurrently, the Pest Control Division of the Ministry of Environmental Protection carried out intensive vector trapping, while mosquito pool testing was routinely performed by the Medical Entomology Laboratory and the Central Virology Laboratory (Ministry of Health). To amplify avian surveillance, the Veterinary Services launched a public reporting campaign via a dedicated mobile application ("Bird Button"), integrated with municipal 106 hotlines. Local authorities and the Nature and Parks Authority facilitated the collection of wild bird carcasses for cost-free laboratory diagnostic testing at the Central Kimron Veterinary Institute, Ministry of Agriculture.
Results: The 2024 summer season culminated in 930 confirmed human cases, resulting in 73 deaths, predominantly affecting individuals over the age of 60. The outbreak was characterized by unusually intense viral circulation, reflected in high positivity rates in humans, birds, and mosquito pools. Simultaneously, massive wild bird mortality was recorded, with 319/1047 birds testing positive for WNV, including 221 hooded crows (Corvus cornix) and 33 domestic pigeons (Columba livia), exhibiting severe neurological signs or death between mid-June and the end of September 2024. The hooded crow is the most common bird species found in close proximity to humans in Israel, and its susceptibility to West Nile virus is substantially higher than that of other synanthropic bird species, outweighing differences in relative abundance. Commercial poultry sectors remained symptomatically unaffected due to geographical segregation and low susceptibility of chickens.
Environmental trapping successfully isolated WNV-positive mosquito pools across central Israel. An environmental root-cause analysis identified a critical infrastructure failure at a wastewater treatment plant in Ramat HaSharon (Central district) which served as an extensive breeding habitat for the mosquito vectors Culex perexiguus and Culex pipiens, likely driving regional viral amplification and spillover.
Conclusion & One Health Significance: The 2024 WNV outbreak underscores the critical intersection of failing environmental infrastructure, vector proliferation, wildlife sentinels, and human vulnerability. This crisis highlights that human health cannot be safeguarded and cannot be isolated from environmental risks management and wildlife monitoring. The deployment of cross-sectoral tools—such as citizen avian reporting, free veterinary diagnostics, and targeted environmental investigations—demonstrates the operational necessity of the One Health framework in predicting, detecting, and mitigating vector-borne zoonotic threats.
Tight multidisciplinary cooperation and coordination among all relevant governmental ministries enabled the rapid implementation of surveillance and response activities throughout the outbreak, and very likely contributed to reducing human morbidity and mortality.
Keywords: West Nile Virus; One Health; Vector-Borne Outbreak; Enzootic Surveillance; Environmental Infrastructure; Citizen Reporting.
