The growing public health burden of Aedes mosquito-borne diseases requires a comprehensive understanding of Aedes species biology, ecology, and vector competence. Eco-epidemiological modelling of Aedes vector species has grown significantly in recent years, driven by the increasing reports of outbreaks in endemic and non-endemic temperate areas, as well as the latitudinal and altitudinal range expansion of these vectors. A prominent example is the Asian tiger mosquito, Aedes albopictus, a competent arbovirus vector that has spread across most continents through the movement of humans and goods. Species distribution models and mechanistic models have been used to predict the spatio-temporal distribution and dynamics of this vector. However, despite the potential of these models to capture the vector distribution and dynamics, integrating them into practical monitoring, surveillance, and vector control activities remains challenging, often due to a lack of communication and model co-development between scientists and public health stakeholders. This paper reports the results of a workshop on vector modelling held in Bologna (Italy) in September 2024, which brought together European experts in disease modelling, public health stakeholders, and medical entomologists. The workshop identified key priorities for advancing the operational use of Aedes-focused quantitative models, including sustained investment in surveillance, improved representation of environmental and biological drivers, standardisation of model outputs, and the establishment of long-term, co-produced modelling frameworks embedded within public health workflows.

The increasing geographical spread, abundance and activity of invasive Aedes mosquitoes are cause of concern for public health at local and global scales. These species transmit diseases such as dengue, Chikungunya, Yellow Fever, and Zika, which can cause outbreaks in endemic and non-endemic settings. Unlike temperature, whose impact on key entomological traits has been extensively studied, the impact of water availability on Aedes traits and hence population dynamics has been largely overlooked. This scoping review aims to fill this gap by compiling the published laboratory evidence of the effect of precipitation and water availability on the bionomics of invasive Aedes species (including Ae. albopictus, Ae. aegypti, Ae. japonicus, and Ae. koreicus). We found eleven studies investigating the effect of water availability on the bionomics of invasive Aedes mosquitoes, none of which were conducted with Ae. japonicus or Ae. koreicus. The effect of rainfall intensity and duration on the survival and development of Ae. albopictus and Ae. aegypti was investigated by three studies, which showed that heavy and long-lasting precipitation leads to higher immature mortality in both species. The impact of water availability on the survival to adulthood, development, and oviposition behaviour of Ae. albopictus and Ae. aegypti was explored by seven studies. The studies reported higher survival and faster development in water volumes below 2 litres, and that the amount of water contained can favour oviposition, with females laying significantly more eggs in containers that are half full compared to those that are full. An additional two studies explored the relationship between evaporation and adult survival and body size of Ae. albopictus and Ae. aegypti. Evaporation was found to have a detrimental effect on the survival and egg hatching of Ae. albopictus, but not of Ae. aegypti. Interestingly Ae. albopictus was also found to have bigger body sizes when exposed to evaporation. This review provides a summary of the experimental evidence currently published on the effect of water availability on invasive Aedes traits, and highlights how key research questions and knowledge gaps still remain. These should be addressed by future experiments to be able to generate data-driven predictions of the geographical expansion of these species under changing rainfall patterns, and the potential impact of containment strategies.

Abstract Background West Nile virus (WNV) is a vector-borne zoonotic pathogen maintained in an enzootic cycle between birds and mosquitoes which is considered a significant public health concern in Europe, particularly in relation to its recent increase in reported human cases and range expansion. While a comprehensive understanding of the virus’s epidemiological dynamics is essential to inform effective prevention and control strategies, to date significant knowledge gaps remain in quantifying interspecific differences within the complex avian communities involved in WNV circulation. Globally, WNV-infection has indeed been documented across more than 300 bird species, however, whether and how inter-specific differences in avian hosts traits affect the spread of WNV is still largely unknown. A substantial body of research has investigated how epidemiological traits, such as the duration of infection and competence, influence WNV dynamics. However, much less is known about the role of avian demography. Methodology/Principal findings We therefore investigated through mathematical modelling the role of avian demographic traits in shaping patterns of mosquito WNV infection dynamics in northern Italy (Lombardy Region, 2016-2018). We focused on the effects of annual offspring production, timing and synchrony of breeding which ultimately affect seasonal abundance of competent avian hosts. We highlighted that timing of breeding has the greatest effect on the number of infected mosquitoes, while annual offspring production influences the timing of the infection peak. Our simulations provide evidence that non-corvid species can have a key impact on WNV transmission. Conclusion/Significance These results can support future research by providing priority bird species to direct further studies and by suggesting that the acknowledgment of spatio-temporal variation in the abundance of competent avian hosts plays a key role in the development of effective surveillance strategies and mosquito control actions. Author summary West Nile virus (WNV) is endemic in Italy and represents a significant public health threat in Europe, with increasing cases of severe neuroinvasive disease in humans in recent years. Surveillance data reveal marked spatial and temporal variability in infection dynamics, suggesting that key drivers of WNV transmission remain poorly understood. The contribution of different bird species (over 300 are implicated in the WNV cycle) is often overlooked despite evidence that species-specific traits are critical determinants of WNV infection dynamics. Few studies have examined birds’ demographic traits, despite their well-established importance in shaping infection dynamics across diseases. Given the challenges in collecting detailed wildlife data, we employed mechanistic models to explore transmission scenarios and test whether avian demographic traits influence bird species’ roles in WNV transmission and maintenance in Lombardy. Our findings demonstrate that brood size, hatching synchrony, and hatching time significantly affect estimated WNV prevalence in mosquitoes.

BACKGROUNDWest Nile virus (WNV) is a zoonotic mosquito-borne pathogen increasingly reported in Europe.AIMWe aimed to characterise heterogeneities in the average annual human risk of WNV infection (force of infection, FOI) and in WNV surveillance across Europe.METHODSWe conducted a systematic review following the PRISMA guidelines to identify serological studies on WNV in humans with IgG-based assays in Europe. We then used mathematical models fitted to both age-stratified serosurvey and case data to reconstruct spatially explicit FOI estimates, the sensitivity of syndromic surveillance and age-dependent trends in case reporting.RESULTSWe extracted 92 serosurvey datasets from 21 countries. Based on 10 age-stratified serosurvey datasets from Greece, Hungary, Italy, Romania and Spain and case data from seven countries (Austria, Cyprus, Greece, Hungary, Italy, Romania and Spain), we estimated the WNV FOI for 119 European nomenclature of territorial units for statistics level (NUTS) 0-3 regions. We found evidence of spatial heterogeneities in transmission intensity and estimated that on average less than 0.2% of human WNV infections were notified, with country variability and age-dependent trends in the propensity of reporting WNV disease.CONCLUSIONThis study shows that the intensity of WNV transmission, the average annual incidence of infection and the sensitivity of surveillance are heterogeneous across Europe. Due to differences in case reporting across countries, the incidence of reported WNV cases does not necessarily reflect the same proportion of WNV infections and hence the actual infection incidence, which highlights the importance of conducting WNV seroprevalence surveys.

Among the several Asian Aedes species that have established in Europe over recent decades, Aedes koreicus has received comparatively little research attention since its first detection in Belgium in 2008, despite its remarkable ability to colonise montane and peri-alpine localities at elevations beyond the reach of its congener Aedes albopictus. Nearly two decades after its European detection, a systematic synthesis of the available evidence and a structured assessment of research and operational priorities are overdue. This paper presents the results of a scoping review of the scientific literature on Ae. koreicus combined with the outcomes of a multidisciplinary expert workshop held in Trento, Italy, in February 2026, which brought together 41 researchers and practitioners from six European countries with expertise in mosquito surveillance, medical entomology, genomics, ecological modelling and public health practice. Through the literature search we obtained a total of 334 articles, of which 91 were eventually included, all published after 2011. Most of the studies were carried out within Europe, focusing mostly on mosquito surveillance. Building upon the scoping review, the workshop identified key priorities for advancing knowledge and operational responses to Ae. koreicus, including strengthened surveillance in montane and lowland areas, improved characterisation of its vector competence and competitive interactions with co-occurring Aedes species, and more effective communication strategies for engaging the public and citizen scientists in monitoring efforts.

The Asian tiger mosquito (Aedes albopictus), a competent vector for dengue, chikungunya, and Zika viruses, has expanded rapidly across temperate Europe. European vector surveillance typically operates May to October, assuming winter diapause precludes activity and transmission risk. However, recent field observations suggest sustained egg-laying winter activity in southern European populations, potentially extending arbovirus transmission risk. We aimed to quantify winter ovitrap activity patterns across temperate Europe and assess their implications for mosquito surveillance across temperate Europe. In this multi-scale observational study, we deployed standardised ovitraps from October 2024 to May 2025 across 12 locations spanning 35–48°N (Italy, France, Switzerland, Austria; n=345 trap-weeks), complemented by 14-year longitudinal surveillance (2011–2025) from Emilia-Romagna, northern Italy (n=1999 trap-weeks across 10 municipalities). We used binomial generalised additive models to quantify the effects of photoperiod, temperature, and precipitation on ovitrap positivity while accounting for spatial heterogeneity. We calculated trap effort requirements for reliable winter detection and assessed temporal trends in spring versus autumn activity. Winter ovitrap positivity was common and geographically structured. Photoperiod was the dominant driver (p<0.001), with southern Mediterranean sites maintaining detection probabilities >20% throughout December–January, while northern sites showed near-complete cessation. Temperature significantly modulated activity with reduced detection below 10°C. Substantial spatial heterogeneity persisted, indicating that local factors override climate variables. Spring positivity (January–May) was 73% lower than autumn (October–December; p<2×10⁻¹¹), reflecting overwintering population bottlenecks. Fourteen-year regional trends showed no significant autumn increase, but a modest spring increase, though confounded by temperature and potential surveillance artefacts. Power analysis revealed current surveillance (median 10 traps per site-week) substantially exceeds autumn requirements (4 traps for 80% detection) but falls short for spring (13 traps required). Ovipositing winter activity of Ae. albopictus in temperate Europe is widespread and structured by photoperiod and geography rather than being rare or negligible. Current May-October surveillance paradigms miss substantial autumn activity and likely underestimate population persistence capacity. Persistent egg-laying winter activity in Mediterranean climates, though homodynamicity was not detected, combined with recent evidence of lower-than-expected thermal transmission thresholds, suggests that arbovirus risk assessment should consider extended seasonal windows or better be estimated at an annual time frame. While our results demonstrate that winter monitoring is essential to uncover ecological patterns, multi-year continental surveys are required to confirm patterns and disentangle the drivers of seasonal variability. These results provide a foundation for adaptive surveillance strategies as Ae. albopictus continues expanding into increasingly temperate regions under climate change.

Background Culex pipiens is the primary vector of West Nile virus (WNV) and Usutu virus (USUV) in Europe. Despite modelling studies suggest that global warming can facilitate WNV and USUV transmission in the European Mediterranean region, to date limited quantitative data on the effects of temperature on the longevity and reproductive traits of European Cx. pipiens mosquitoes have been generated. Methods We conducted a scoping review to identify existing data on how constant temperature affects Cx. pipiens longevity and reproductive traits, including fecundity and gonotrophic cycle length. To address key knowledge gaps, we carried out controlled laboratory experiments using field-derived Cx. pipiens reared from larvae collected in northern Italy. Female mosquitoes were kept at four constant temperatures (12°C, 25°C, 28°C, and 31°C), provided with blood meals, and monitored over time for survival and oviposition until death. Results The scoping review showed that the current evidence base is limited, with only five relevant studies identified. We also found evidence that life-history traits differ between laboratory colonies and field populations across geographic contexts. In our experiments, mosquito longevity declined monotonically with increasing temperature between 25 and 31°C, ranging from 62 to 33 days on average. Egg-laying rates peaked at 28°C, with reproductive traits showing substantial individual and seasonal variation and no clear temperature relationship. No mosquito completed more than one gonotrophic cycle. At 12°C, blood-fed females survived three months without further blood feeding or oviposition. Conclusions Our study integrates context-specific knowledge on how constant temperature affects Cx. pipiens longevity and reproduction and fills an important knowledge gap by providing experimental data based on field-collected European mosquitoes. We also provide preliminary evidence that seasonality, in addition to temperature, may influence mosquito reproduction. Importantly, field-collected, non-diapausing, blood-fed females appear to enter a state of quiescence at low temperatures, suggesting a potential overwintering mechanism for arboviruses. Together, these findings improve our understanding of Cx. pipiens biology and have implications for WNV and USUV transmission in European settings.

BACKGROUND:West Nile virus (WNV) is among the most widespread arboviruses and has become a seasonal threat in temperate regions. Sustained in an enzootic bird-mosquito cycle, with humans and horses as incidental hosts, its geographic range has expanded in recent decades due to ongoing climatic and ecological changes. While most infections are asymptomatic or mild, a minority progress to neuroinvasive disease with high morbidity and long-term sequelae. This review summarizes current knowledge on epidemiology, pathogenesis, clinical spectrum, diagnostic challenges, therapeutic options, prevention, and research gaps. DISCUSSION:Lineages 1 and 2 co-circulate in Europe, where repeated large outbreaks highlight WNV adaptability to warmer summers, altered rainfall, and expanded mosquito habitats driven by recent ecological shifts. After inoculation, replication occurs in keratinocytes and dendritic cells, amplification in lymph nodes, and dissemination to visceral organs and the central nervous system. Neuroinvasion depends on viral proteins and host immune responses. Severe disease is associated with advanced age, immunosuppression, comorbidities, and genetic susceptibility. Clinical manifestations range from febrile illness to meningitis, encephalitis, or acute flaccid myelitis. Persistent neurological and functional sequelae are common, adding to disease burden. Diagnosis relies on molecular and serological tests, limited by short viremia and cross-reactivity with other flaviviruses. No approved antiviral therapy exists; management is supportive. Experimental antivirals, monoclonal antibodies, and interferon have shown mixed results. Vaccine candidates have progressed to phase 1-2 trials, but none are licensed for humans. Prevention relies on integrated vector control, veterinary surveillance, and donor screening, framed within a One Health approach. CONCLUSION:WNV exemplifies the impact of global ecological change on zoonotic diseases. Strengthening surveillance, refining diagnostics, and advancing antivirals and vaccines through multidisciplinary collaboration are essential to mitigate future outbreaks.

West Nile virus (WNV) is one of the most widespread arboviruses globally and is maintained primarily through a bird-mosquito-bird transmission cycle, while other vertebrates play more limited roles. Host contributions to transmission depend on both infection evidence in natural populations (reflecting exposure and susceptibility) and reservoir competence, determined by the magnitude and duration of viraemia sufficient to infect mosquitoes. Despite extensive surveillance and experimental research, no comprehensive, standardised resource has integrated evidence on host exposure and infection in natural populations together with experimental data on host competence across vertebrate taxa. Here, we present two harmonised datasets compiled through a systematic literature review: (i) a WNV host prevalence dataset, summarising infection and serological evidence in wild and captive vertebrates; and (ii) a WNV host competence dataset, derived from controlled experimental infections. The prevalence dataset aggregates records from 541 studies across 91 countries (1950-2023), comprising 535,568 tested individuals from 1,801 vertebrate species. The WNV host competence dataset compiles 113 experimental infection studies covering 103 species and 3,030 individuals, and provides standardised time-resolved viraemia and survival data with accompanying metadata, enabling reconstruction and/or modelling of species-specific viraemia trajectories and the derivation of quantitative competence metrics. Both datasets use standardised taxonomy and incorporate synonym crosswalks to facilitate linkage with trait databases, phylogenetic trees and species distribution products. Together, these resources provide a unified foundation for macroecological analyses, surveillance gap assessment, and modelling multi-host WNV transmission dynamics.

Aedes koreicus, a temperate mosquito native to East Asia, is rapidly expanding across Europe. While diapause is documented in this species, the combined effects of temperature and exposure duration on egg overwintering success remain poorly understood. We experimentally quantified the hatching success of diapausing and non-diapausing Ae. koreicus eggs exposed to five fluctuating cold regimes (ranging from 5 °C to -20 °C) for periods of 2 to 30 days, using a constant 5 °C control. Under control conditions, hatching success was similar between both egg types. However, cold exposure markedly reduced success, with non-diapausing eggs experiencing a significantly stronger decline (0.343 ± 0.029 SE) than diapausing eggs (0.487 ± 0.031 SE). Generalised linear beta-binomial models revealed a strong, nonlinear interaction between temperature, exposure duration, and egg type. Notably, diapausing eggs exhibited a hatching peak at intermediate subzero temperatures (-5 °C to -10 °C) and maintained higher success during prolonged cold exposure. Conversely, non-diapausing eggs were substantially more sensitive, showing sharper declines across the thermal gradient. These results align with the overwintering strategies of other temperate Aedes species, such as Ae. albopictus, and emphasize the necessity of considering both temperature and duration when assessing cold tolerance. Our findings provide essential parameters for phenological modeling and improve predictions of Ae. koreicus invasion potential in colder regions under variable climatic conditions.

BackgroundWest Nile Virus (WNV) is a zoonotic arbovirus maintained in a transmission cycle between Culex mosquitoes and birds, occasionally spilling over into humans. The impact of avian biodiversity on WNV circulation remains debated, with studies reporting both negative and positive correlations (dilution and amplification effects respectively) across different settings. In Europe, this relationship remains largely unexplored, particularly in regions with high WNV transmission, such as Emilia-Romagna in Northern Italy.MethodsWe explored the association between avian biodiversity and WNV circulation in Culex mosquitoes in Emilia-Romagna using 11 years (2013-2023) of entomological surveillance data paired with two avian data sources. We calculated avian biodiversity indices (Shannon's, Simpson's, and Chao2) from observation records from the Farmland Bird Index project and applied linear regression models to assess their relationship with WNV detection frequency. Moreover, we used Bayesian spatiotemporal regression models and gridded weekly avian abundance estimates from the eBird project to analyse the associations between avian species richness indices and WNV transmission risk quantified by vector index (VI) at 68 geolocated mosquito traps across the region.ResultsWe observed consistent negative associations between WNV detection frequency in the Culex population and avian biodiversity indices, supporting the dilution effect hypothesis (DEH). We found that non-passerine species richness was negatively associated with VI while passerine species richness showed a positive association after adjusting for covariates and spatial random effects. These findings suggest that passerines may amplify WNV transmission, whereas the presence of non-passerine species is associated with reductions in WNV circulation.SignificanceThis study provides the first empirical evidence supporting the DEH for WNV in Europe. These findings have important implications for biodiversity conservation and integrated public health surveillance activities across Europe.

Background:Tick-borne encephalitis (TBE), caused by tick-borne encephalitis virus (TBEV), is a zoonotic disease that can lead to severe neurological symptoms. Given the increasing number of reported human TBE cases in Europe, we developed a spatio-temporal predictive model to infer the year-to-year probability of human TBE occurrence across Europe at the regional and municipal administrative levels. Methods:We derived the distribution of human TBE cases at the regional level during 2017-2022 by using data provided by the European Centre for Disease Prevention and Control (ECDC), and at the municipal level by using data provided by Austria, Finland, Italy, Lithuania, and Slovakia. We modeled the probability of presence of human TBE cases at the regional and municipal levels for the period 2017-2025 with a boosted regression trees model, including covariates that affect both the natural hazard of virus circulation and human exposure to tick bites. Findings:Areas with the highest probability of human TBE infections are located in central-eastern Europe, the Baltic states, and along the coastline of Nordic countries. Our results highlight a statistically significant rising trend in human TBE risk not only in north-western, but also in south-western European countries. Such areas are characterised by the presence of key tick host species, forested areas, intense human activity in forests, steep drops in late summer temperatures and high precipitation amounts during the driest months. The model showed good predictive performance, with a mean AUC of 0.84 (SD = 0.03), sensitivity of 0.83 (SD = 0.01), and specificity of 0.80 (SD = 0.01) at the regional level, and a mean AUC of 0.82 (SD = 0.03), sensitivity of 0.83 (SD = 0.01), and specificity of 0.69 (SD = 0.01) at the municipal level. Interpretation:With ongoing climate and land use changes, the number of human TBE cases is likely to increase and spread into new areas. This highlights the importance of predictive models that can identify potential risk areas to support disease prevention and control efforts by public health authorities. The approach adopted, by fitting a One Health framework and leveraging lagged covaries, enables timely one-year-ahead predictions and enhances our current understanding of TBE risk under a global change scenario.

Various modelling techniques are available to understand the temporal and spatial variations of the phenology of species. Scientists often rely on correlative models, which establish a statistical relationship between a response variable (such as species abundance or presence-absence) and a set of predominantly abiotic covariates. The choice of the modeling approach, i.e., the algorithm, is itself a significant source of variability, as different algorithms applied to the same dataset can yield disparate outcomes. This inter-model variability has led to the adoption of ensemble modelling techniques, among which stacked generalisation, which has recently demonstrated its capacity to produce robust results. Stacked ensemble modelling incorporates predictions from multiple base learners or models as inputs for a meta-learner. The meta-learner, in turn, assimilates these predictions and generates a final prediction by combining the information from all the base learners. In our study, we utilized a recently published dataset documenting egg abundance observations of Aedes albopictus collected using ovitraps. and a set of environmental predictors to forecast the weekly median number of mosquito eggs using a stacked machine learning model. This approach enabled us to (i) unearth the seasonal egg-laying dynamics of Ae. albopictus for 12 years; (ii) generate spatio-temporal explicit forecasts of mosquito egg abundance in regions not covered by conventional monitoring initiatives. Our work establishes a robust methodological foundation for forecasting the spatio-temporal abundance of Ae. albopictus, offering a flexible framework that can be tailored to meet specific public health needs related to this species.

West Nile virus (WNV) is an emerging vector-borne pathogen that is becoming increasingly prevalent in temperate regions. The development of effective intervention strategies is crucial for limiting its spread; however, the adaptability and ubiquity of mosquitoes, combined with the complexity of the WNV transmission cycle, continue to hinder its eradication. This study employs a deterministic compartmental model to evaluate the effectiveness of ten intervention strategies targeting either the mosquito (vector) or avian (host) population in the Lombardy region of Italy. Vector-targeted interventions were more effective than host-targeted measures, with breeding site reduction and larvicide treatments demonstrating the greatest efficacy. In contrast, interventions targeting adult mosquitoes, including adulticide treatments and elimination of overwintering mosquitoes, showed moderate efficacy. Furthermore, the impact of eliminating overwintering mosquitoes gradually diminished over time. Host-targeted strategies, such as bird population reduction, were ineffective and, in some cases, led to increased WNV transmission. The efficacy of all interventions varied temporally, peaking in mid-summer. These findings highlight the importance of prioritising mosquito control, particularly targeting immature stages, to mitigate WNV outbreaks. Our study highlights the critical role of mathematical modelling in designing effective intervention strategies. By providing a structured framework to evaluate and predict the outcomes of various approaches, modelling can aid disease control while optimising resource allocation and minimising environmental impact. Mathematical models, therefore, prove to be powerful tools for balancing public health goals with sustainable practices.

Background/introduction: Tick-borne encephalitis (TBE) is a severe zoonotic neurological infection caused by the TBE virus (member of the Flaviriridae family), and it is considered to be one of the most important tick-borne viral diseases in Europe and Asia. In mainland Europe the main tick species transmitting the TBE virus is Ixodes ricinus. The infection is mostly acquired after a tick bite, but food-borne infection is also possible. TBE is a notifiable disease in EU/EEA since 2012. Despite the availability of a vaccine, its incidence is increasing with the appearance of new foci of virus circulation in areas previously unaffected. TBE prevention and mitigation of spill-over events could be obtained with One Health surveillance, which integrates traditional disease-based surveillance with the monitoring of drivers of disease emergence and early warning signals. This presentation focuses on the principal ecological and climatic drivers shaping TBE emergence in Europe and the use of environmental indexes as proxies for TBE infection risk. Methods: We searched available literature on covariates linked with the circulation of TBEV in Europe and assessed the best predictors for TBE incidence by means of statistical regression, using data on human TBE infections collected by the European Surveillance System (TESSy) and made available by The European Centre for Disease Prevention and Control (ECDC), averaged between 2017 and 2021. We then explored the relationship between the presence of human TBE cases across Europe and the habitat richness index (HRI) by means of binomial regression. Results: Among 31 different covariates, we selected eight variables from the best model, including factors linked to vegetation cover (i.e, Enhanced Vegetation Index and percentage of forested areas), climate (i.e, mean winter temperature, autumnal cooling rate and diurnal temperature range), and the probability of the presence of tick hosts, such as rodents and cervids. We also found a significant parabolic effect of HRI on the probability of the presence of human TBE cases in the European regions included in our dataset, with a TBE risk decline in areas with higher values of HRI. Discussion: In our studies, we summarized and statistically validated the covariates affecting the variability of TBE risk across Europe, which will serve as a basis for developing high-resolution risk models. Furthermore, we considered habitat richness as a proxy for disease risk, and our results suggest that in highly diverse habitats, TBE risk decreases. Conclusion: TBEV distribution is shaped by the interplay of multiple climatic, environmental, and ecological factors that exert a crucial role in the life cycle of ticks and TBEV circulation. We provided insights into the combination of covariates that appear to be crucial in affecting TBEV occurrence in Europe, defined their main data sources and established their interrelation with human TBE incidence at a continental scale. This study support competent authorities in deploying One Health integrated actions in existing and new potential risk areas.

As West Nile Virus (WNV) is expanding its geographical range across Europe, there is an urgent need to characterise and better understand its transmission drivers to inform public health surveillance, disease control, and preparedness planning. We utilised 10 consecutive years of large-scale and fine-resolution WNV entomological field surveillance data from the Emilia-Romagna region in northern Italy, to evaluate the relationships between WNV infection rates in Culex mosquitoes and environmental and climatic conditions as well as WNV presence in the avian reservoir. We used fine-scale spatiotemporal regression models including non-linearities, to assess the drivers of presence and prevalence of WNV-positive mosquitoes. We validated the model estimates against reported cases of human WNV neuroinvasive disease in the region. We found evidence of established hotspots of mosquito WNV infection across multiple years. The presence of WNV in local birds was positively associated with presence and prevalence of WNV-positive mosquitoes (mean regression coefficients: 0.776 (95% CrI, 0.469, 1.08) and 0.226 (95% CrI, 0.053, 0.399) respectively), and the proportion of agricultural land use was positively associated with presence of WNV-positive mosquitoes (4.20 (95% CrI, 2.65, 5.75)). We identified a minimum temperature threshold around 13°C, below which mosquito WNV infection was reduced. Our findings provide evidence of the impact of temperature and environment on Culex populations and WNV infection dynamics at the local level, which were highly correlated with human case reports. The estimated role of the minimum temperature and the observed and projected increase in this variable under climate change suggest that WNV will continue to represent a risk for human and animal health in the region in future decades. Future work should focus on better understanding the mechanisms behind infection drivers, on the optimal implementation of surveillance and control activities around high-risk areas, and on the assessment of how specific land use practices could represent potential solutions to WNV infection.

West Nile virus (WNV) is one of the most threatening mosquito-borne pathogens in Italy where hundreds of human cases were recorded during the last decade. Here, we estimated the WNV incidence in the avian population in the Emilia-Romagna region through a modelling framework which enabled us to eventually assess the fraction of birds that present anti-WNV antibodies at the end of each epidemiological season.We fitted an SIR model to ornithological data, consisting of 18,989 specimens belonging to Corvidae species collected between 2013 and 2022: every year from May to November birds are captured or shot and tested for WNV genome presence. We found that the incidence peaks between mid-July and late August, infected corvids seem on average 17% more likely to be captured with respect to susceptible ones and seroprevalence was estimated to be larger than other years at the end of 2018, consistent with the anomalous number of recorded human infections.Thanks to our modelling study we quantified WNV infection dynamics in the corvid community, which is still poorly investigated despite its importance for the virus circulation. To the best of our knowledge, this is among the first studies providing quantitative information on infection and immunity in the bird population, yielding new important insights on WNV transmission dynamics.

West Nile virus (WNV) is an emerging mosquito-borne pathogen in Europe where it represents a new public health threat. While climate change has been cited as a potential driver of its spatial expansion on the continent, a formal evaluation of this causal relationship is lacking. Here, we investigate the extent to which WNV spatial expansion in Europe can be attributed to climate change while accounting for other direct human influences such as land-use and human population changes. To this end, we trained ecological niche models to predict the risk of local WNV circulation leading to human cases to then unravel the isolated effect of climate change by comparing factual simulations to a counterfactual based on the same environmental changes but a counterfactual climate where long-term trends have been removed. Our findings demonstrate a notable increase in the area ecologically suitable for WNV circulation during the period 1901–2019, whereas this area remains largely unchanged in a no-climate-change counterfactual. We show that the drastic increase in the human population at risk of exposure is partly due to historical changes in population density, but that climate change has also been a critical driver behind the heightened risk of WNV circulation in Europe.

BackgroundWest Nile virus (WNV) is an emerging mosquito-borne pathogen in Serbia, where it has been detected as a cause of infection in humans since 2012. We analyzed and modelled WNV transmission patterns in the country between 2012 and 2023.MethodsWe applied a previously developed modelling approach to quantify epidemiological parameters of interest and to identify the most important environmental drivers of the force of infection (FOI) by means of statistical analysis in the human population in the country.ResultsDuring the study period, 1,387 human cases were recorded, with substantial heterogeneity across years. We found that spring temperature is of paramount importance for WNV transmission, as FOI magnitude and peak timing are positively associated with it. Furthermore, FOI is also estimated to be greater in regions with a larger fraction of older adult people, who are at higher risk to develop severe infections.ConclusionOur results highlight that temperature plays a key role in shaping WNV outbreak magnitude in Serbia, confirming the association between spring climatic conditions and WNV human transmission risk and thus pointing out the importance of this factor as a potential early warning predictor for timely application of preventive and control measures.

Introduction: Caused by the tick-borne encephalitis virus (TBEV), tick-borne encephalitis (TBE) is a zoonotic disease that can cause severe neurological symptoms. Despite the availability of a vaccine, it remains a public health concern in Europe, with an increasing number of reported human cases and new hotspots of virus circulation, also in previously non-endemic areas. To geolocate and predict new areas at risk of human TBE infections, we developed a spatio-temporal predictive model to infer the year-to-year probability of human TBE occurrence across Europe at the regional and municipal administrative levels. Methods: We derived the distribution of human TBE cases at the regional (NUTS-3) level during the period 2017-2022 using data provided by the European surveillance system (TESSy, ECDC), while the distribution of human TBE cases at the municipal level during the same years was obtained using data from five European countries (Austria, Finland, Italy, Lithuania, and Slovakia). We modelled the probability of TBE occurrence at regional and municipal levels for the period 2017-2024 using a boosted regression trees approach, including both hazard and exposure variables affecting TBE risk: climate, land cover, presence of tick hosts to account for the natural hazard of virus circulation, forest road density and human population density as proxies for the probability of human exposure to tick bites. Results: Our modelling framework provides a multi-scale approach to predict yearly variations in the risk of occurrence of human TBE cases in Europe. Our results highlight a significant rising trend in the probability of human infection with TBE not only in north-western, but also in south-western European countries and show that areas at high risk of TBE are characterized by the presence of key tick host species, intense human recreational activity in forests, steep drops in late summer temperatures and high annual precipitation. Discussion: Our study provides a modelling framework for the early annual assessment and identification of European regions and municipalities at risk of human TBE infection, based on covariates reflecting both the hazard and exposure dimensions. Being based on lagged covariates, our approach can also be used to predict risk areas one year in advance, thus supporting surveillance, prevention, and control of human TBE infections by public health authorities. ### Competing Interest Statement The authors have declared no competing interest.