•Arboviruses are still expanding their geographic distribution and causing significant public health impact around the world.•DENV, CHIKV and ZIKV are mosquito-transmitted pathogens posing a threat ...to human health in many regions of the world.•Global travel and trade have facilitated the emergence of vector-borne diseases.•Surveillance of areas close to the forest is important to monitor the emergence of pathogens from their sylvatic cycle.
Arthropod-borne viruses (arboviruses) present a substantial threat to human and animal health worldwide. Arboviruses can cause a variety of clinical presentations that range from mild to life threatening symptoms. Many arboviruses are present in nature through two distinct cycles, the urban and sylvatic cycle that are maintained in complex biological cycles. In this review we briefly discuss the factors driving the emergence of arboviruses, such as the anthropogenic aspects of unrestrained human population growth, economic expansion and globalization. Also the important aspects of viruses and vectors in the occurrence of arboviruses epidemics. The focus of this review will be on dengue, zika and chikungunya viruses, particularly because these viruses are currently causing a negative impact on public health and economic damage around the world.
The clinical outcomes associated with Zika virus (ZIKV) in the Americas have been well documented, but other aspects of the pandemic, such as attack rates and risk factors, are poorly understood. We ...prospectively followed a cohort of 1453 urban residents in Salvador, Brazil, and, using an assay that measured immunoglobulin G3 (IgG3) responses against ZIKV NS1 antigen, we estimated that 73% of individuals were infected during the 2015 outbreak. Attack rates were spatially heterogeneous, varying by a factor of 3 within a community spanning 0.17 square kilometers. Preexisting high antibody titers to dengue virus were associated with reduced risk of ZIKV infection and symptoms. The landscape of ZIKV immunity that now exists may affect the risk for future transmission.
Transmission of arthropod-borne viruses (arboviruses) involves infection and replication in both arthropod vectors and vertebrate hosts. Nearly all arboviruses are RNA viruses with high mutation ...frequencies, which leaves them vulnerable to genetic drift and fitness losses owing to population bottlenecks during vector infection, dissemination from the midgut to the salivary glands and transmission to the vertebrate host. However, despite these bottlenecks, they seem to avoid fitness declines that can result from Muller's ratchet. In addition, founder effects that occur during the geographic introductions of human-amplified arboviruses, including chikungunya virus and Zika virus, can affect epidemic and endemic circulation, as well as virulence. In this Review, we discuss the role of genetic drift following population bottlenecks and founder effects in arboviral evolution and spread, and the emergence of human disease.
Dengue--quo tu et quo vadis? Chen, Rubing; Vasilakis, Nikos
Viruses,
09/2011, Letnik:
3, Številka:
9
Journal Article, Book Review
Recenzirano
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Dengue viruses (DENV) are by far the most important arboviral pathogens in the tropics around the world, putting at risk of infection nearly a third of the global human population. DENV are members ...of the genus Flavivirus in the Family Flaviviridae and comprise four antigenically distinct serotypes (DENV-1-4). Although they share almost identical epidemiological features, they are genetically distinct. Phylogenetic analyses have revealed valuable insights into the origins, epidemiology and the forces that shape DENV evolution in nature. In this review, we examine the current status of DENV evolution, including but not limited to rates of evolution, selection pressures, population sizes and evolutionary constraints, and we discuss how these factors influence transmission, pathogenesis and emergence.
Dengue viruses (DENV) are the most important arboviral pathogens in tropical and subtropical regions throughout the world, putting at risk of infection nearly a third of the global human population. ...Evidence from the historical record suggests a long association between these viruses and humans. The transmission of DENV includes a sylvatic, enzootic cycle between nonhuman primates and arboreal mosquitoes of the genus
Aedes, and an urban, endemic/epidemic cycle between
Aedes aegypti, a mosquito with larval development in peridomestic water containers, and human reservoir hosts. DENV are members of the genus
Flavivirus in the Family
Flaviviridae and comprise of 4 antigenically distinct serotypes (DENV-1–4). Although they are nearly identical epidemiologically, the 4 DENV serotypes are genetically quite distinct. Utilization of phylogenetic analyses based on partial and/or complete genomic sequences has elucidated the origins, epidemiology (genetic diversity, transmission dynamics and epidemic potential), and the forces that shape DENV molecular evolution (rates of evolution, selection pressures, population sizes, putative recombination and evolutionary constraints) in nature. In this review, we examine how phylogenetics have improved understanding of DENV population dynamics and sizes at various stages of infection and transmission, and how this information may influence pathogenesis and improve our ability to understand and predict DENV emergence.
Zika virus (ZIKV) emerged from obscurity in 2013 to spread from Asia to the South Pacific and the Americas, where millions of people were infected, accompanied by severe disease including ...microcephaly following congenital infections. Phylogenetic studies have shown that ZIKV evolved in Africa and later spread to Asia, and that the Asian lineage is responsible for the recent epidemics in the South Pacific and Americas. However, the reasons for the sudden emergence of ZIKV remain enigmatic. Here we report evolutionary analyses that revealed four mutations, which occurred just before ZIKV introduction to the Americas, represent direct reversions of previous mutations that accompanied earlier spread from Africa to Asia and early circulation there. Our experimental infections of Aedes aegypti mosquitoes, human cells, and mice using ZIKV strains with and without these mutations demonstrate that the original mutations reduced fitness for urban, human-amplifed transmission, while the reversions restored fitness, increasing epidemic risk. These findings include characterization of three transmission-adaptive ZIKV mutations, and demonstration that these and one identified previously restored fitness for epidemic transmission soon before introduction into the Americas. The initial mutations may have followed founder effects and/or drift when the virus was introduced decades ago into Asia.
The four dengue virus (DENV) serotypes that circulate among humans emerged independently from ancestral sylvatic progenitors that were present in non-human primates, following the establishment of ...human populations that were large and dense enough to support continuous inter-human transmission by mosquitoes. This ancestral sylvatic-DENV transmission cycle still exists and is maintained in non-human primates and Aedes mosquitoes in the forests of Southeast Asia and West Africa. Here, we provide an overview of the ecology and molecular evolution of sylvatic DENV and its potential for adaptation to human transmission. We also emphasize how the study of sylvatic DENV will improve our ability to understand, predict and, ideally, avert further DENV emergence.
ICTV Virus Taxonomy Profile: Rhabdoviridae Walker, Peter J; Blasdell, Kim R; Calisher, Charles H ...
Journal of general virology,
04/2018, Letnik:
99, Številka:
4
Journal Article
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The family Rhabdoviridae comprises viruses with negative-sense (-) single-stranded RNA genomes of 10.8-16.1 kb. Virions are typically enveloped with bullet-shaped or bacilliform morphology but can ...also be non-enveloped filaments. Rhabdoviruses infect plants and animals including mammals, birds, reptiles and fish, as well as arthropods which serve as single hosts or act as biological vectors for transmission to animals or plants. Rhabdoviruses include important pathogens of humans, livestock, fish and agricultural crops. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of Rhabdoviridae, which is available at www.ictv.global/report/rhabdoviridae.
The Asian lineage of Zika virus (ZIKV) has recently caused epidemics and severe disease. Unraveling the mechanisms causing increased viral transmissibility and disease severity requires experimental ...systems. We report an infectious cDNA clone of ZIKV that was generated using a clinical isolate of the Asian lineage. The cDNA clone-derived RNA is infectious in cells, generating recombinant ZIKV. The recombinant virus is virulent in established ZIKV mouse models, leading to neurological signs relevant to human disease. Additionally, recombinant ZIKV is infectious for Aedes aegypti and thus provides a means to examine virus transmission. The infectious cDNA clone was further used to generate a luciferase ZIKV that exhibited sensitivity to a panflavivirus inhibitor, highlighting its potential utility for antiviral screening. This ZIKV reverse genetic system, together with mouse and mosquito infection models, may help identify viral determinants of human virulence and mosquito transmission as well as inform vaccine and therapeutic strategies.
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•An infectious cDNA clone of Zika virus and a luciferase reporter virus were developed•Recombinant Zika virus is virulent in A129 and AG129 mice•Recombinant Zika virus is highly infectious for Aedes aegypti mosquitos•The luciferase Zika virus can be used for antiviral drug discovery
Zika virus (ZIKV) is causing devastating epidemics with severe disease. Shan et al. generated an infectious cDNA clone of ZIKV as well as a luciferase reporter virus. Recombinant ZIKV is virulent in mice and infectious in Aedes aegypti and thus may help identify viral determinants of virulence and transmission.
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