-
Pathogens and Global Health Jul 2018Eastern Europe (EE) has been severely affected by mosquito-borne viruses (moboviruses). In this review, we summarize the epidemiology of moboviruses, with particular... (Review)
Review
Eastern Europe (EE) has been severely affected by mosquito-borne viruses (moboviruses). In this review, we summarize the epidemiology of moboviruses, with particular attention to West Nile virus (WNV). The study of WNV human cases in EE between 2010 and 2016, revealed that the epidemiology of WNV in EE is complex with the combination of introduction of different WNV strains from lineages 1 and 2, and the establishment of endemic cycles. We found a positive correlation between the risk of WNV re-emergence in an area and the number of human cases reported in the previous year. We also report the main ecological and biological characteristics of the key mosquito species vectors of moboviruses. Recent expansion of invasive mosquito species in EE, mainly Aedes albopictus but also Aedes aegypti and Culex quinquefasciatus, may result in new scenarios with an increased risk of transmission of moboviruses. Main gaps of knowledge in relation to moboviruses and their vectors in EE are identified. Understanding the epidemiology of moboviruses in EE is essential for the improvement of their surveillance and the control of the diseases they cause.
Topics: Aedes; Animals; Culex; Disease Transmission, Infectious; Europe, Eastern; Humans; Mosquito Vectors; Risk Assessment; West Nile Fever; West Nile virus
PubMed: 29979950
DOI: 10.1080/20477724.2018.1483567 -
Communications Biology Jan 2022It is unclear whether West Nile virus (WNV) circulates endemically in Portugal. Despite the country's adequate climate for transmission, Portugal has only reported four...
It is unclear whether West Nile virus (WNV) circulates endemically in Portugal. Despite the country's adequate climate for transmission, Portugal has only reported four human WNV infections so far. We performed a review of WNV-related data (1966-2020), explored mosquito (2016-2019) and land type distributions (1992-2019), and used climate data (1981-2019) to estimate WNV transmission suitability in Portugal. Serological and molecular evidence of WNV circulation from animals and vectors was largely restricted to the south. Land type and climate-driven transmission suitability distributions, but not the distribution of WNV-capable vectors, were compatible with the North-South divide present in serological and molecular evidence of WNV circulation. Our study offers a comprehensive, data-informed perspective and review on the past epidemiology, surveillance and climate-driven transmission suitability of WNV in Portugal, highlighting the south as a subregion of importance. Given the recent WNV outbreaks across Europe, our results support a timely change towards local, active surveillance.
Topics: Animal Distribution; Animals; Climate; Culicidae; Humans; Mosquito Vectors; Portugal; Seasons; Species Specificity; Weather; West Nile Fever; West Nile virus
PubMed: 35013546
DOI: 10.1038/s42003-021-02969-3 -
Journal of Medical Entomology Oct 2019The introduction of West Nile virus (WNV) to North America in 1999 and its subsequent rapid spread across the Americas demonstrated the potential impact of arboviral... (Review)
Review
The introduction of West Nile virus (WNV) to North America in 1999 and its subsequent rapid spread across the Americas demonstrated the potential impact of arboviral introductions to new regions, and this was reinforced by the subsequent introductions of chikungunya and Zika viruses. Extensive studies of host-pathogen-vector-environment interactions over the past two decades have illuminated many aspects of the ecology and evolution of WNV and other arboviruses, including the potential for pathogen adaptation to hosts and vectors, the influence of climate, land use and host immunity on transmission ecology, and the difficulty in preventing the establishment of a zoonotic pathogen with abundant wildlife reservoirs. Here, we focus on outstanding questions concerning the introduction, spread, and establishment of WNV in the Americas, and what it can teach us about the future of arboviral introductions. Key gaps in our knowledge include the following: viral adaptation and coevolution of hosts, vectors and the virus; the mechanisms and species involved in the large-scale spatial spread of WNV; how weather modulates WNV transmission; the drivers of large-scale variation in enzootic transmission; the ecology of WNV transmission in Latin America; and the relative roles of each component of host-virus-vector interactions in spatial and temporal variation in WNV transmission. Integrative studies that examine multiple factors and mechanisms simultaneously are needed to advance our knowledge of mechanisms driving transmission.
Topics: Adaptation, Biological; Animals; Central America; Host-Pathogen Interactions; Humans; North America; South America; West Nile Fever; West Nile virus; Zoonoses
PubMed: 31549719
DOI: 10.1093/jme/tjz151 -
Viruses Oct 2023Flaviviruses are a family of enveloped viruses with a positive-sense RNA genome, transmitted by arthropod vectors. These viruses are known for their broad cellular... (Review)
Review
Flaviviruses are a family of enveloped viruses with a positive-sense RNA genome, transmitted by arthropod vectors. These viruses are known for their broad cellular tropism leading to infection of multiple body systems, which can include the central nervous system. Neurologic effects of flavivirus infection can arise during both acute and post-acute infectious periods; however, the molecular and cellular mechanisms underlying post-acute sequelae are not fully understood. Here, we review recent studies that have examined molecular and cellular mechanisms that may contribute to neurologic sequelae following infection with the West Nile virus, Japanese encephalitis virus, Zika virus, dengue virus, and St. Louis encephalitis virus. Neuronal death, either from direct infection or due to the resultant inflammatory response, is a common mechanism by which flavivirus infection can lead to neurologic impairment. Other types of cellular damage, such as oxidative stress and DNA damage, appear to be more specific to certain viruses. This article aims to highlight mechanisms of cellular damage that are common across several flavivirus members and mechanisms that are more unique to specific members. Our goal is to inspire further research to improve understanding of this area in the hope of identifying treatment options for flavivirus-associated neurologic changes.
Topics: Animals; Humans; Culicidae; Mosquito Vectors; Flavivirus Infections; Flavivirus; West Nile virus; Zika Virus; Zika Virus Infection
PubMed: 38005878
DOI: 10.3390/v15112200 -
Journal of Vector Borne Diseases 2023West Nile virus (WNV) is a rapidly spreading mosquito-transmitted zoonotic flavivirus. Mosquitoes belonging to the genus Culex are incriminated as the principal vectors... (Review)
Review
West Nile virus (WNV) is a rapidly spreading mosquito-transmitted zoonotic flavivirus. Mosquitoes belonging to the genus Culex are incriminated as the principal vectors of the virus, which causes West Nile fever (WNF) in humans. Manifestations of WNF include a mild, self-limiting, flu-like illness, which in severe cases (rare) may progress to encephalitis, resulting in life-threatening consequences. WNV is geographically distributed worldwide, covering Africa, the Americas, Europe, and Asia (except Antarctica). The virus exists in a bird-mosquito transmission cycle in nature, with humans and horses as incidental/accidental hosts. The virus can infect a large variety of hosts worldwide, i.e., about 300 birds and around 70 different mosquito species belonging to several genera. For a long time, it was believed that WNV was not highly virulent and caused only mild infection globally. However, the recent frequent and increasing incidence of clinically severe WNV infections, such as encephalitis in humans and horses with significant mortality, has been reported in the Americas, Europe, and several East Asian countries. The emergence of lineage 2 strains endemic to Africa, with epidemic potential in humans and horses in Europe, is considered a serious global health concern. Although WNV is known to circulate in India since 1952, its re-emergence with severe neuro-invasive pathogenic potential in humans in Assam, Kerala, West Bengal and Tamil Nadu states signals urgent efforts to understand the dynamics of circulating strains with regard to its vector, hosts, and environment. This could be done by prioritizing "One Health" approach for developing effective preventive and control strategies. In view of the global interest, we present an overview of the circulating genetic lineages of WNV in India in comparison with the global scenario. In addition, we stress on holistic approaches of "One Health" strategy as the current need of the hour for designing effective preventive and control strategies in the country.
Topics: Humans; Animals; Horses; West Nile virus; India; Mosquito Vectors; West Nile Fever; Culicidae; Birds
PubMed: 37843232
DOI: 10.4103/0972-9062.374039 -
Viruses Aug 2017Apoptosis is a type of programmed cell death that regulates cellular homeostasis by removing damaged or unnecessary cells. Its importance in host defenses is highlighted... (Review)
Review
Apoptosis is a type of programmed cell death that regulates cellular homeostasis by removing damaged or unnecessary cells. Its importance in host defenses is highlighted by the observation that many viruses evade, obstruct, or subvert apoptosis, thereby blunting the host immune response. Infection with Flaviviruses such as Japanese encephalitis virus (JEV), Dengue virus (DENV) and West Nile virus (WNV) has been shown to activate several signaling pathways such as endoplasmic reticulum (ER)-stress and AKT/PI3K pathway, resulting in activation or suppression of apoptosis in virus-infected cells. On the other hands, expression of some viral proteins induces or protects apoptosis. There is a discrepancy between induction and suppression of apoptosis during flavivirus infection because the experimental situation may be different, and strong links between apoptosis and other types of cell death such as necrosis may make it more difficult. In this paper, we review the effects of apoptosis on viral propagation and pathogenesis during infection with flaviviruses.
Topics: Animals; Apoptosis; Cell Death; Cell Survival; Dengue Virus; Encephalitis Virus, Japanese; Endoplasmic Reticulum; Flavivirus; Flavivirus Infections; Host-Pathogen Interactions; Humans; Life Cycle Stages; Lymphoma, B-Cell; Neoplasms; Phosphatidylinositol 3-Kinases; Signal Transduction; Stress, Physiological; West Nile virus
PubMed: 28846635
DOI: 10.3390/v9090243 -
Human Vaccines & Immunotherapeutics 2019West Nile virus (WNV) is a widely spread human pathogenic arthropod-borne virus. It can lead to severe, sometimes fatal, neurological disease. Over the last two decades,... (Review)
Review
West Nile virus (WNV) is a widely spread human pathogenic arthropod-borne virus. It can lead to severe, sometimes fatal, neurological disease. Over the last two decades, several vaccine candidates for the protection of humans from WNV have been developed. Some technologies were transferred into clinical testing, but these approaches have not yet led to a licensed product. This review summarizes the current status of a human WNV vaccine and discusses reasons for the lack of clinically advanced product candidates. It also discusses the problem of immunological cross-reactivity between flaviviruses and how it can be addressed during vaccine development.
Topics: Animals; Antibodies, Viral; Clinical Trials as Topic; Cross Reactions; Humans; Viral Envelope Proteins; West Nile Fever; West Nile Virus Vaccines; West Nile virus
PubMed: 31116691
DOI: 10.1080/21645515.2019.1621149 -
Brain Pathology (Zurich, Switzerland) Sep 2015Arboviruses (Arthropod-borne viruses) include several families of viruses (Flaviviridae, Togaviradae, Bunyaviradae, Reoviradae) that are spread by arthropod vectors,... (Review)
Review
Arboviruses (Arthropod-borne viruses) include several families of viruses (Flaviviridae, Togaviradae, Bunyaviradae, Reoviradae) that are spread by arthropod vectors, most commonly mosquitoes, ticks and sandflies. The RNA genome allows these viruses to rapidly adapt to ever-changing host and environmental conditions. Thus, these virus families are largely responsible for the recent expansion in geographic range of emerging viruses including West Nile virus (WNV), dengue virus and Chikungunya virus. This review will focus on WNV, especially as it has progressively spread westward in North America since its introduction in New York in 1999. By 2003, WNV infections in humans had reached almost all lower 48 contiguous United States (US) and since that time, fluctuations in outbreaks have occurred. Cases decreased between 2008 and 2011, followed by a dramatic flair in 2012, with the epicenter in the Dallas-Fort Worth region of Texas. The 2012 outbreak was associated with an increase in reported neuroinvasive cases. Neuroinvasive disease continues to be a problem particularly in the elderly and immunocompromised populations, although WNV infections also represented the second most frequent cause of pediatric encephalitis in these same years. Neuropathological features in cases from the 2012 epidemic highlight the extent of viral damage that can occur in the CNS.
Topics: Aged; Animals; Brain; Encephalitis, Viral; Female; History, 20th Century; History, 21st Century; Humans; Male; Middle Aged; West Nile virus
PubMed: 26276026
DOI: 10.1111/bpa.12280 -
PLoS Pathogens Jan 2024West Nile virus (WNV) outbreaks in birds, humans, and livestock have occurred in multiple areas in Europe and have had a significant impact on animal and human health....
BACKGROUND
West Nile virus (WNV) outbreaks in birds, humans, and livestock have occurred in multiple areas in Europe and have had a significant impact on animal and human health. The patterns of emergence and spread of WNV in Europe are very different from those in the US and understanding these are important for guiding preparedness activities.
METHODS
We mapped the evolution and spread history of WNV in Europe by incorporating viral genome sequences and epidemiological data into phylodynamic models. Spatially explicit phylogeographic models were developed to explore the possible contribution of different drivers to viral dispersal direction and velocity. A "skygrid-GLM" approach was used to identify how changes in environments would predict viral genetic diversity variations over time.
FINDINGS
Among the six lineages found in Europe, WNV-2a (a sub-lineage of WNV-2) has been predominant (accounting for 73% of all sequences obtained in Europe that have been shared in the public domain) and has spread to at least 14 countries. In the past two decades, WNV-2a has evolved into two major co-circulating clusters, both originating from Central Europe, but with distinct dynamic history and transmission patterns. WNV-2a spreads at a high dispersal velocity (88km/yr-215 km/yr) which is correlated to bird movements. Notably, amongst multiple drivers that could affect the spread of WNV, factors related to land use were found to strongly influence the spread of WNV. Specifically, the intensity of agricultural activities (defined by factors related to crops and livestock production, such as coverage of cropland, pasture, cultivated and managed vegetation, livestock density) were positively associated with both spread direction and velocity. In addition, WNV spread direction was associated with high coverage of wetlands and migratory bird flyways.
CONCLUSION
Our results suggest that-in addition to ecological conditions favouring bird- and mosquito- presence-agricultural land use may be a significant driver of WNV emergence and spread. Our study also identified significant gaps in data and the need to strengthen virological surveillance in countries of Central Europe from where WNV outbreaks are likely seeded. Enhanced monitoring for early detection of further dispersal could be targeted to areas with high agricultural activities and habitats of migratory birds.
Topics: Animals; Humans; West Nile virus; West Nile Fever; Phylogeography; Europe; Disease Outbreaks
PubMed: 38271294
DOI: 10.1371/journal.ppat.1011880 -
Viruses Dec 2022West Nile virus (WNV) is a mosquito-borne virus potentially causing serious illness in humans and other animals. Since 2004, several studies have highlighted the...
West Nile virus (WNV) is a mosquito-borne virus potentially causing serious illness in humans and other animals. Since 2004, several studies have highlighted the progressive spread of WNV Lineage 2 (L2) in Europe, with Italy being one of the countries with the highest number of cases of West Nile disease reported. In this paper, we give an overview of the epidemiological and genetic features characterising the spread and evolution of WNV L2 in Italy, leveraging data obtained from national surveillance activities between 2011 and 2021, including 46 newly assembled genomes that were analysed under both phylogeographic and phylodynamic frameworks. In addition, to better understand the seasonal patterns of the virus, we used a machine learning model predicting areas at high-risk of WNV spread. Our results show a progressive increase in WNV L2 in Italy, clarifying the dynamics of interregional circulation, with no significant introductions from other countries in recent years. Moreover, the predicting model identified the presence of suitable conditions for the 2022 earlier and wider spread of WNV in Italy, underlining the importance of using quantitative models for early warning detection of WNV outbreaks. Taken together, these findings can be used as a reference to develop new strategies to mitigate the impact of the pathogen on human and other animal health in endemic areas and new regions.
Topics: Animals; Humans; West Nile virus; West Nile Fever; Italy; Europe; Culicidae
PubMed: 36680076
DOI: 10.3390/v15010035