Impact of climate change on West Nile virus distribution in South America

Assessing dengue seroprevalence among people living with HIV (PLWH) in rome, Italy: Insights from the 2023 Italian autochthonous outbreak

BACKGROUND

Global warming has facilitated the spread of mosquito-borne diseases, including dengue, to non-endemic areas like Italy. People living with HIV (PLWH) are at increased risk of severe dengue, especially during secondary infections, but current vaccination options are constrained by safety considerations. This study assesses the seroprevalence of IgG anti-DENV among PLWH in Italy, after the 2023 Italian autochthonous outbreak.

METHODS

This cross-sectional study enrolled PLWH from July to November 2023 in Rome during the abovementioned outbreak. Blood samples were collected and analyzed for IgG anti-DENV using ELISA. Participants were stratified by country of birth and those with immune profiles suitable for live attenuated virus vaccination were identified. Cryopreserved serum samples from 2021 to 2022 were tested to trace the timing of infections.

RESULTS

We included 475 PLWH of whom 37 tested positive for IgG anti-DENV, resulting in an overall seroprevalence of 7.79 % (95 % CI 5.54-10.6). The seroprevalence was significantly higher among PLWH born in DENV-endemic countries (37.14 %) compared to Italian (2.86 %). Notably, among the Italian participants, three individuals who had not traveled outside Italy in the past 12 months showed seroconversion during the 2023 outbreak, providing further evidence of autochthonous dengue transmission in the country. This finding underscores the growing relevance of dengue as an emerging public health concern in Italy. Of the 37 seropositive individuals, 34 (91.9 %) had a CD4 count ≥200 cells/μl, indicating that a significant portion of the at-risk population could safely be vaccinated.

CONCLUSIONS

Many PLWH have been exposed to DENV, with some experiencing seroconversion during the 2023 outbreak. Most of these individuals could feasibly receive live attenuated virus vaccination without significant risks, but further studies are needed to confirm vaccine safety for PLWH.

West Nile Virus (WNV): One-Health and Eco-Health Global Risks

West Nile virus (WNV) is an important zoonotic pathogen belonging to the Flaviviridae family, which is endemic in some areas and emerging in others. WNV is transmitted by blood-sucking mosquitoes of the genus Culicoides, Aedes, and Anopheles, and the infection can cause different clinical symptoms. The most common and benign illness in humans is West Nile fever (WNF), but a lethal neurological disease (WNND), related to the neuro-invasiveness of WNV lineage 2, represents the highest health risk of WNV infection. The neuro-clinical form is recognized in mammals (land and cetaceans), particularly in humans (elderly or immunosuppressed) and in horses, avian species, and wildlife animals ranging free or in a zoological setting. This review highlights the most relevant data regarding epidemiology, virology, pathogenesis and immunity, clinical signs and differential diagnosis, pathology and imaging, histopathology and gross pathology, economic impact, influence of climate change, and surveillance of WNV. Climate change has favored the wide spread of WNV in many areas of the globe and consequent One-Health and Eco-Health emergencies, influencing the health of human beings, animals, and ecosystems.

Effects of climate change on the occurrence and distribution of Western equine encephalitis virus in South America

OBJECTIVES

The Western equine encephalitis virus (WEEV) is a globally relevant vector-borne pathogen that causes encephalitis. The role of environmental variables in the epidemiology of WEEV has become greater in the context of climate change. In December 2023, a significant resurgence of WEEV began in South America, with major ongoing outbreaks in Argentina and Uruguay. In this study, we employed a machine learning algorithm to model the distribution of WEEV in South America, considering both present and future scenarios.

STUDY DESIGN

Ecological retrospective study.

METHODS

We conducted a modelling study to identify areas with the highest prevalence of WEEV in South America, based on confirmed human and equine cases during the 2023/2024 outbreak and climatic variables. Our analysis utilised Maxent software, a machine learning algorithm for species distribution modelling.

RESULTS

Our results indicate that environmental variables, particularly thermal seasonality and annual rainfall, can directly influence the occurrence of WEEV, leading to increased virus incidence. Consequently, high-risk areas may shift in the future. Countries, such as Paraguay, Venezuela, Colombia, and various regions in Brazil, particularly the Northeast, Midwest, and the Pantanal biomes, will be significantly impacted, drastically altering the current distribution of WEEV.

CONCLUSIONS

The ongoing WEEV outbreak in South America is concerning because it coincides with migratory bird stopovers. These birds are natural hosts that can spread the virus to unaffected areas. Our results will help to identify priority areas for developing preventive measures and establishing epidemiological surveillance.

Unveiling spatial patterns of West Nile virus emergence in northern Greece, 2010-2023

The Region of Central Macedonia (RCM) in Northern Greece recorded the highest number of human West Nile virus (WNV) infections in Greece, despite considerable local mosquito control actions. We examined spatial patterns and associations of mosquito levels, infected mosquito levels, and WNV human cases (WNVhc) across the municipalities of this region over the period 2010-2023 and linked it with climatic characteristics. We combined novel entomological and available epidemiological and climate data for the RCM, aggregated at the municipality level and used Local and Global Moran's I index to assess spatial associations of mosquito levels, infected mosquito levels, and WNVhc. We identified areas with strong interdependencies between adjacent municipalities in the Western part of the region. Furthermore, we employed a Generalized Linear Mixed Model to first, identify the factors driving the observed levels of mosquitoes, infected mosquitoes and WNVhc and second, estimate the influence of climatic features on the observed levels. This modeling approach indicates a strong dependence of the mosquito levels on the temperatures in winter and spring and the total precipitation in early spring, while virus circulation relies on the temperatures of late spring and summer. Our findings highlight the significant influence of climatic factors on mosquito populations (∼60 % explained variance) and the incidence of WNV human cases (∼40 % explained variance), while the unexplained ∼40 % of the variance suggests that targeted interventions and enhanced surveillance in identified hot-spots can enhance public health response.

Impact of climate change on the global circulation of West Nile virus and adaptation responses: a scoping review

BACKGROUND

West Nile virus (WNV), the most widely distributed flavivirus causing encephalitis globally, is a vector-borne pathogen of global importance. The changing climate is poised to reshape the landscape of various infectious diseases, particularly vector-borne ones like WNV. Understanding the anticipated geographical and range shifts in disease transmission due to climate change, alongside effective adaptation strategies, is critical for mitigating future public health impacts. This scoping review aims to consolidate evidence on the impact of climate change on WNV and to identify a spectrum of applicable adaptation strategies.

MAIN BODY

We systematically analyzed research articles from PubMed, Web of Science, Scopus, and EBSCOhost. Our criteria included English-language research articles published between 2007 and 2023, focusing on the impacts of climate change on WNV and related adaptation strategies. We extracted data concerning study objectives, populations, geographical focus, and specific findings. Literature was categorized into two primary themes: 1) climate-WNV associations, and 2) climate change impacts on WNV transmission, providing a clear understanding. Out of 2168 articles reviewed, 120 met our criteria. Most evidence originated from North America (59.2%) and Europe (28.3%), with a primary focus on human cases (31.7%). Studies on climate-WNV correlations (n = 83) highlighted temperature (67.5%) as a pivotal climate factor. In the analysis of climate change impacts on WNV (n = 37), most evidence suggested that climate change may affect the transmission and distribution of WNV, with the extent of the impact depending on local and regional conditions. Although few studies directly addressed the implementation of adaptation strategies for climate-induced disease transmission, the proposed strategies (n = 49) fell into six categories: 1) surveillance and monitoring (38.8%), 2) predictive modeling (18.4%), 3) cross-disciplinary collaboration (16.3%), 4) environmental management (12.2%), 5) public education (8.2%), and 6) health system readiness (6.1%). Additionally, we developed an accessible online platform to summarize the evidence on climate change impacts on WNV transmission ( https://2xzl2o-neaop.shinyapps.io/WNVScopingReview/ ).

CONCLUSIONS

This review reveals that climate change may affect the transmission and distribution of WNV, but the literature reflects only a small share of the global WNV dynamics. There is an urgent need for adaptive responses to anticipate and respond to the climate-driven spread of WNV. Nevertheless, studies focusing on these adaptation responses are sparse compared to those examining the impacts of climate change. Further research on the impacts of climate change and adaptation strategies for vector-borne diseases, along with more comprehensive evidence synthesis, is needed to inform effective policy responses tailored to local contexts.

Comparison of West Nile Virus Disease in Humans and Horses: Exploiting Similarities for Enhancing Syndromic Surveillance

West Nile virus (WNV) neuroinvasive disease threatens the health and well-being of horses and humans worldwide. Disease in horses and humans is remarkably similar. The occurrence of WNV disease in these mammalian hosts has geographic overlap with shared macroscale and microscale drivers of risk. Importantly, intrahost virus dynamics, the evolution of the antibody response, and clinicopathology are similar. The goal of this review is to provide a comparison of WNV infection in humans and horses and to identify similarities that can be exploited to enhance surveillance methods for the early detection of WNV neuroinvasive disease.