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Oropouche fever is an emerging zoonotic disease caused by Oropouche virus (OROV), an arthropod transmitted Orthobunyavirus circulating in South and Central America. During the last 60 years, more than 30 epidemics and over half a million clinical cases attributed to OROV infection have been reported in Brazil, Peru, Panama, Trinidad and Tobago. OROV fever is considered the second most frequent arboviral febrile disease in Brazil after dengue fever. OROV is transmitted through both urban and sylvatic transmission cycles, with the primary vector in the urban cycle being the anthropophilic biting midge Culicoides paraensis. Currently, there is no evidence of direct human-to-human OROV transmission. OROV fever is usually either undiagnosed due to its mild, self-limited manifestations or misdiagnosed because its clinical characteristics are similar to dengue, chikungunya, Zika and yellow fever, including malaria as well. At present, there is no specific antiviral treatment, and in the absence of a vaccine for effective prophylaxis of human populations in endemic areas, the disease prevention relies solely on vector control strategies and personal protection measures. OROV fever is considered to have the potential to spread across the American continent and under favorable climatic conditions may expand its geographic distribution to other continents. In view of OROV’s emergence, increased interest for formerly neglected tropical diseases and within the One Health concept, the existing knowledge and gaps of knowledge on OROV fever are reviewed.

Half of the world's population is at risk of arthropod-borne virus (arbovirus) infections. Several arbovirus infections have been associated with Guillain-Barré syndrome (GBS). We investigated whether arboviruses are driving GBS beyond epidemic phases of transmission and studied the antibody response to glycolipids. The protocol of the International Guillain-Barré syndrome Outcome Study (IGOS), an observational prospective cohort study, was adapted to a case-control design. Serum samples were tested for a recent infection with Zika virus (ZIKV), dengue virus (DENV), chikungunya (CHIKV) virus, hepatitis E virus, Epstein-Barr virus (EBV), cytomegalovirus (CMV), Campylobacter jejuni, and Mycoplasma pneumoniae, and for antibodies to glycolipids. Forty-nine patients were included from Brazil (63%), Argentina (14%), and Malaysia (22%). Evidence of a recent infection was found in 27/49 (55%) patients: C jejuni (n = 15, 31%), M pneumoniae (n = 5, 10%), CHIKV (n = 2, 4%), EBV (n = 1, 2%), C jejuni and M pneumoniae (n = 2, 4%), CMV and DENV (n = 1, 2%), and C jejuni and DENV (n = 1, 2%). In 22 patients, 35 paired controls were collected. Odds ratio for recent infections did not significantly differ between cases and controls. No typical anti-ganglioside antibody binding was associated with recent arbovirus infection. We conclude that arbovirus infections occur in GBS patients outside of epidemic viral transmission, although not significantly more than in controls. Broad infection and anti-ganglioside antibody serology are important to establish the most likely pathogenic trigger in GBS patients. Larger studies are necessary to determine the association between arboviruses and GBS.

West Nile virus (WNV) is a mosquito-borne flavivirus that can cause severe neurological disease in humans, for which there is no treatment or vaccine. From 2009 to 2018, California has reported more human disease cases than any other state in the United States. We sought to identify smaller geographic areas within the 10 California counties with the highest number of WNV cases that accounted for disproportionately large numbers of human cases from 2009 to 2018. Eleven areas, consisting of groups of high-burden ZIP codes, were identified in nine counties within southern California and California's Central Valley. Despite containing only 2% of California's area and 17% of the state's population, these high-burden ZIP codes accounted for 44% of WNV cases reported and had a mean annual incidence that was 2.4 times the annual state incidence. Focusing mosquito control and public education efforts in these areas would lower WNV disease burden.

Background The Zika virus (ZIKV) epidemic of 2015/2016 spread throughout numerous countries. It emerged in mainland Latin America and spread to neighboring islands, including the Caribbean island of Barbados. Recent studies have indicated that the virus must have already been circulating in local mosquito populations in Brazil for almost 2 years before it was identified by the World Health Organization in 2015. Metagenomic detection assays have the potential to detect emerging pathogens without prior knowledge of their genomic nucleic acid sequence. Yet their applicability as vector surveillance tools has been widely limited by the complexity of DNA populations from field-collected mosquito preparations. The aim of this study was to investigate local vector biology and characterize metagenomic arbovirus diversity in Aedes mosquitoes during the ongoing 2015/2016 ZIKV epidemic. Methods We performed a short-term vector screening study on the island of Barbados during the ongoing 2015/2016 ZIKV epidemic, where we sampled local Aedes mosquitoes. We reanalyzed mosquito viral microbiome data derived from standard Illumina MiSeq sequencing to detect arbovirus sequences. Additionally, we employed deep sequencing techniques (Illumina HiSeq) and designed a novel bait capture enrichment assay to increase sequencing efficiency for arbovirus sequences from complex DNA samples. Results We found that Aedes aegypti seemed to be the most likely vector of ZIKV, although it prevailed at a low density during the observed time period. The number of detected viruses increased with sequencing depth. Arbovirus sequence enrichment of metagenomic DNA preparations allowed the detection of arbovirus sequences of two different ZIKV genotypes, including a novel one. To our knowledge, this is the first report of the S3116W mutation in the NS5 gene region of ZIKV polyprotein. Conclusions The metagenomic arbovirus detection approach presented here may serve as a useful tool for the identification of epidemic-causing arboviruses with the additional benefit of enabling the collection of phylogenetic information on the source. Apart from detecting more than 88 viruses using this approach, we also found evidence of novel ZIKV variants circulating in the local mosquito population during the observed time period. Graphical abstract

El virus de chikunguña (CHIKV) es un Alfavirus perteneciente al grupo denominado del Viejo Mundo; estos son virus artritogénicos que causan una enfermedad febril caracterizada por artralgias y mialgias. Aunque la muerte por CHIKV es poco frecuente, la enfermedad puede llegar a ser incapacitante y generar un amplio espectro de manifestaciones atípicas, como complicaciones cardiovasculares, respiratorias, oculares, renales y dérmicas, entre otras. Cuando el dolor articular persiste por tres o más meses, da lugar a la forma crónica de la enfermedad denominada reumatismo inflamatorio crónico poschikunguña, el cual es la principal secuela de la enfermedad. Se considera que este virus no es neurotrópico, sin embargo, puede afectar el sistema nervioso central y generar secuelas graves y permanentes, principalmente, en niños y ancianos.En África, Asia y Europa se habían reportado anteriormente brotes epidémicos por CHIKV, pero solo hasta finales del 2013 se documentó la introducción del virus a las Américas; desde entonces, el virus se ha propagado a 45 países o territorios del continente y el número de casos acumulados ascendió a cerca de dos millones en dos años.Esta revisión describe de manera general la biología molecular del virus, sus manifestaciones clínicas, su patogénesis y las principales complicaciones posteriores a la infección. Además, reúne la información de la epidemia en Colombia y el continente americano publicada entre el 2014 y el 2020.

Mosquitoes of the genus Aedes are the main vectors of many viruses, e.g. dengue and Zika, which affect millions of people each year and for which there are limited treatment options. Understanding how Aedes mosquitoes tolerate high viral loads may lead to better disease control strategies. Elucidating endogenous viral elements (EVEs) within vector genomes may give exploitable biological insights. Previous studies have reported the presence of a large number of EVEs in Aedes genomes. Here we investigated if flavivirus EVEs are conserved across populations and different Aedes species by using ~ 500 whole genome sequence libraries from Aedes aegypti and Aedes albopictus, sourced from colonies and field mosquitoes across continents. We found that nearly all flavivirus EVEs in the Ae. aegypti reference genome originate from four separate putative viral integration events, and that they are highly conserved across geographically diverse samples. By contrast, flavivirus EVEs in the Ae. albopictus reference genome originate from up to nine distinct integration events and show low levels of conservation, even within samples from narrow geographical ranges. Our analysis suggests that flaviviruses integrated as long sequences and were subsequently fragmented and shuffled by transposable elements. Given that EVEs of Ae. aegypti and Ae. albopictus belong to different phylogenetic clades and have very differing levels of conservation, they may have different evolutionary origins and potentially different functional roles. Graphical Abstract

An emerging infectious disease first identified in central China in 2009, severe fever with thrombocytopenia syndrome (SFTS) was found to be caused by a novel phlebovirus. Since SFTSV was first identified, epidemics have occurred in several East Asian countries. With the escalating incidence of SFTS and the rapid, worldwide spread of SFTSV vector, it is clear this virus has pandemic potential and presents an impending global public health threat. In this review, we concisely summarize the latest findings regarding SFTSV, including vector and virus transmission, genotype diversity and epidemiology, probable pathogenic mechanism, and clinical presentation of human SFTS. Ticks most likely transmit SFTSV to animals including humans; however, human-to-human transmission has been reported. The majority of arbovirus transmission cycle includes vertebrate hosts, and potential reservoirs include a variety of both domestic and wild animals. Reports of the seroprevalence of SFTSV in both wild and domestic animals raises the probability that domestic animals act as amplifying hosts for the virus. Major clinical manifestation of human SFTS infection is high fever, thrombocytopenia, leukocytopenia, gastrointestinal symptoms, and a high case-fatality rate. Several animal models were developed to further understand the pathogenesis of the virus and aid in the discovery of therapeutics and preventive measures., Virology: An emerging tick-borne disease Severe fever with thrombocytopenia syndrome (SFTS), a tick-borne infectious disease caused by a novel phlebovirus, is a growing global health concern. The main symptoms are high fever, low platelet and white blood cell levels, and gastrointestinal problems. The disease was first identified in China in 2009, and several SFTS epidemics have occurred in East Asia, with mortality rates of between 6 and 27 per cent. Researchers in South Korea led by Young Ki Choi at Chungbuk National University, Cheongju, review the latest research into SFTS virus and disease, including transmission, genetic diversity, epidemiology, pathology and clinical features, and pandemic potential. Animal models are helping researchers understand the virus and disease and develop treatments and vaccines.

Yellow fever is an endemic disease in America caused by an arbovirus that circulates in the sylvatic cycle between nonhuman primates and mosquitoes of the genera Sabethes Robineau-Desvoidy and Haemagogus Williston. The main goal of this work is to report the distribution patterns of these genera in Argentina through an updated database built from published records as well as from own sample collections. These genera are represented in Argentina by a total of 18 species distributed in 14 provinces and 10 ecoregions. The ecoregions with greatest biodiversity were Paranense Forest, Yungas, Campos and Malezales. This database will also allow generating distribution maps for these mosquito genera, and their respective species in Argentina, to establish areas with high probability of viral circulation that are an essential input for vector surveillance, as a tool for public health decision-makers.

Eastern equine encephalitis virus (EEEV) is the most pathogenic arbovirus endemic to the United States. Studies have demonstrated Florida’s role as a regional reservoir for the virus and its ability to support year-round transmission. Previous research has developed risk index models for mapping locations most at risk for EEEV transmission. We compared vector abundance, vector feeding behavior, potential host species, and fauna presence at high versus low–moderate risk sites during the winter and spring. Predicted high-risk sites had a significantly greater abundance of mosquitoes overall, including Culiseta melanura (Coquillett) (Diptera: Culicidae), the primary enzootic vector of EEEV. Twenty host species were identified from Cs. melanura bloodmeals, with the majority taken from avian species. Culiseta melanura largely fed upon the Northern Cardinal (Cardinalis cardinalis (Passeriformes: Cardinalidae)), which accounted for 20–24.4% of the bloodmeals obtained from this species in years 1 and 2, respectively. One EEEV-positive mosquito pool (Cs. melanura) and nine EEEV seropositive sentinel chickens were confirmed during winter-spring collections from high-risk sites; no seropositive chickens nor mosquito pools were found at the low–moderate risk sites. These results suggest that high-risk sites for EEEV activity are characterized by habitats that support populations of Cs. melanura and which may also provide ample opportunities to feed upon Northern Cardinals. The overall low level of mosquito populations during the winter also suggests that control of Cs. melanura populations in winter at high-risk sites may prove effective in reducing EEEV transmission during the peak summer season.

From 2008 to 2017, the city of Abidjan, Côte d’Ivoire experienced several Aedes-borne disease epidemics which required control of the vector mosquito population based on the reduction of larval habitats and insecticidal sprays for adult mosquitoes. This study was undertaken to assess the insecticide susceptibility status of Aedes aegypti (Linnaeus) in the city of Abidjan. Immature Ae. aegypti were sampled from several larval habitats within seven communes of Abidjan and reared to adults. Three to five days old F1 emerged adults were tested for susceptibility using insecticide-impregnated papers and the synergist piperonyl butoxide (PBO) following WHO bioassay guidelines. The results showed that Ae. aegypti populations from Abidjan were resistant to 0.1% propoxur, and 1% fenitrothion, with mortality rates ranging from 0% to 54.2%. Reduced susceptibility (93.4–97.5% mortality) was observed to 0.05% deltamethrin, 0.75% permethrin, 0.05% lambda-cyhalothrin, 5% malathion, and 0.8% chlorpyrifos-methyl. This reduced susceptibility varied depending on the insecticide and the collection site. The restoration of mortality when the mosquitoes were pre-exposed to the synergist PBO suggests that increased activity of oxidases could be contributing to resistance. Three kdr mutations (V410L, V1016I, and F1534C) were present in populations tested, with low frequencies for the Leu410 (0.28) and Ile1016 (0.32) alleles and high frequencies for the Cys1534 allele (0.96). These findings will be used to inform future arbovirus vector control activities in Abidjan.

Background The stay-at-home orders imposed in early April 2020 due to the COVID-19 pandemic in various states complicated mosquito control activities across the United States (US), and Florida was no exception. Mosquito control programs are the first line of defense against mosquito-borne pathogens. The purpose of this study was to examine the capabilities of Florida mosquito programs to implement key mosquito measures during the COVID-19 pandemic lockdown. Methods Using a self-administered online survey, we examined the capabilities of all Florida mosquito control programs (both state-approved mosquito districts, N = 63; and open programs, N = 27) at a time when the state of Florida was still under heightened awareness of, stay-at-home orders and planning a phase 1 reopening over the COVID-19 pandemic (June to July 2020). The final sample included mosquito control programs structured as the Board of County Commissioners (BOCC) (n = 42), independent tax district (n = 16), municipal (n = 10), and health or emergency department (n = 5). We used descriptive statistics to summarize information about the characteristics of responding programs, their implemented mosquito control and surveillance activities. wWe used bivariate analysis to compare the characteristics of responding programs and the self-reported mosquito measures. Results Of the recruited mosquito control programs, 73 completed the survey (81.1% response rate; 73/90). Of these, 57.5% (n = 42) were Board of County Commissioners (BOCC) mosquito control programs, 21.9% (n = 16) were independent tax district programs, 13.7% (n = 10) were municipal mosquito control programs, and only 6.8% (n = 5) were either health or emergency department mosquito control programs. Except for arbovirus surveillance, most programs either fully or partially performed larval (61.8%) and adult (78.9%) surveillance; most programs conducted species-specific control for Aedes aegypti (85.2%, n = 54), Aedes albopictus (87.3%, n = 55), Culex quinquefasciatus (92.1%, n = 58), and Culex nigripalpus (91.9%, n = 57). Conclusions Findings underscore the importance of ongoing mosquito control activities, and suggest that Florida mosquito control programs are vigilant and have significant capability to handle potential mosquito-borne disease threats, but arbovirus surveillance systems (laboratory testing of mosquito pools and testing of human and nonhuman specimens for arboviruses) are needed during pandemics as well.

Relevance.Naturalandclimaticconditions,a variety of species composition of arthropods and vertebrates determine the possibility of circulation of arboviruses in the Volgograd region. The existence of natural foci of some arbovirus infections and the possibility of the formation of others suggests the need for annual monitoring of the causative agents of arbovirus diseases.Аim.EvaluationoftheresultsofmonitoringofarbovirusinfectionsintheVolgogradregionin2019.Materials and methods:806bloodserumsamplesfromdonors,44bloodserumsamplesfromfebrilesickpeople,300bloodserumsamplesfromhorsesand94poolsofblood-suckingmosquitoeswereexaminedbyimmunofernalanalysis.ResultofthestudyofserumsamplesfromdonorsintheVolgogradregion,in140(17.4%)of806werefoundtohaveantibodiestothepathogenofWestNilefever(in35(4.3%)– IgM, in 105 (13.0%) – IgG), in 7 (2.2%) of 319 – to the Crimean hemorrhagic fever virus (in 4 (1.3%) – IgM, in 3 (0.9%) –IgG), and in 7 (2.9%) of 240 – IgG to the viruses of the California serogroup. Specific antibodies against viruses of Sindbis, Batai and Uukuniemi in the samples was not detected. The largest number of positive samples with the presence of IgG and IgM to the West Nile virus was found among residents of Volgograd (61 out of 240, 25.4%) and Volzhsky (25 out of 100, 25, 0%). Among 44 blood serums of febrile patients, 1 sample (2.3%) was found to contain an antigen of the Sindbis virus, and 2 samples (4.5%) – antigens California serogroup viruses. Specific immunoglobulins against West Nile virus were detected in 84 (28%) of 300 blood serums of farm animals (horses). In the study of 94 samples of field material (blood-sucking mosquitoes), West Nile virus antigen was detected in 14 (14.9%), Sindbis virus – in one sample (1.0%), Batai virus – in four samples (4.2%). Conclusions:theobtainedresults,alongwiththecirculationofWestNilevirusandCrimeanhemorrhagicfevervirusvirusintheVolgogradregion,indicatethepresenceofSindbis,BataiandCaliforniaserogroupvirusesandnecessitatefurtherstudyoftheirroleintheinfectiouspathologyofthepopulation.

Background: Increasing arbovirus infections have been a global burden in recent decades. Many countries have experienced the periodic emergence of arbovirus diseases. However, information on the prevalence of arboviruses is largely unknown or infrequently updated because of the lack of surveillance studies, especially in Africa. Methods: A surveillance study was conducted in Gabon, Central Africa, on arboviruses, which are a major public health concern in Africa, including: West Nile virus (WNV), dengue virus (DENV), Zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), and Rift Valley fever virus (RVFV). Serological and molecular assays were performed to investigate past infection history and the current status of infection, using serum samples collected from healthy individuals and febrile patients, respectively. Results: The overall seroprevalence during 2014˗2017 was estimated to be 25.3% for WNV, 20.4% for DENV, 40.3% for ZIKV, 60.7% for YFV, 61.2% for CHIKV, and 14.3% for RVFV. No significant differences were found in the seroprevalence of any of the viruses between the male and female populations. However, a focus on the mean age in each arbovirus-seropositive individual showed a significantly younger age in WNV- and DENV-seropositive individuals than in CHIKV-seropositive individuals, indicating that WNV and DENV caused a relatively recent epidemic in the region, whereas CHIKV had actively circulated before. Of note, this indication was supported by the detection of both WNV and DENV genomes in serum samples collected from febrile patients after 2016. Conclusions: This study revealed the recent re-emergence of WNV and DENV in Gabon as well as the latest seroprevalence state of the major arboviruses, which indicated the different potential risks of virus infections and virus-specific circulation patterns. This information will be helpful for public health organizations and will enable a rapid response towards these arbovirus infections, thereby preventing future spread in the country., BMC Infectious Diseases, 21, art. no. 265; 2021

Chikungunya virus (CHIKV) is a (re)emerging arbovirus and the causative agent of chikungunya fever. In recent years, CHIKV was responsible for a series of outbreaks, some of which had serious economic and public health impacts in the affected regions. So far, no CHIKV-specific antiviral therapy or vaccine has been approved. This review gives a brief summary on CHIKV epidemiology, spread, infection and diagnosis. It furthermore deals with the strategies against emerging diseases, drug development and the possibilities of testing antivirals against CHIKV in vitro and in vivo. With our review, we hope to provide the latest information on CHIKV, disease manifestation, as well as on the current state of CHIKV vaccine development and post-exposure therapy.

Purpose of Review This review aims to describe briefly the general information of arboviruses dengue, Zika, and chikungunya infections and emphasize the clinical manifestations of each, to help identify and make a quick diagnosis of each. Recent Findings The most relevant advances in the study of these arboviruses’ infections have been in the epidemiological distribution, mainly due to international travel, migration, and climate change; in the clinical manifestations of these diseases, the development of clinical decision-making software, which can help improve the management and outcomes of these patients; and in the prevention of this disease. Summary Although arboviruses infections constitute a clinical challenge for the attending physician in the scope of a febrile returning traveler, a thorough clinical history and exam can help to aid diagnostic reasoning. The characteristics of the rash are a very helpful clue in the evaluation of these patients. Currently, there are clinical decision aid tools that help to get the diagnosis more quickly.

ObjectiveTo estimate the age- and nationality-specific West Nile virus (WNV) seroprevalence in select Middle East and North Africa (MENA) populations residing in Qatar. MethodsSera were collected from male blood donors attending Hamad Medical Corporation. A total of 1,948 sera were tested for anti-WNV antibodies using Serion ELISA classic IgG and IgM kits. ResultsOverall, seroprevalence estimates of WNV-specific IgG and IgM antibodies were 10.4% and 3.3%, respectively. Country-specific WNV-specific IgG seroprevalence was estimated to be 37.0% (34/92) in Sudanese, 33.0% in Egyptians (66/200), 13.0% (26/200) in Indians, 10.6% (11/104) in Iranians, 10.2% (14/137) in Yemenis, 9.2% (18/195) in Pakistanis, 7.0% ( 14/199) in Jordanians, 5.4% (6/111) in Filipinos, 2.5% (5/200) in Palestinians, 2.5% (5/200) in Syrians, 1.5% (3/200) in Qataris, and 0.9% (1/110) in Lebanese. Seroprevalence of WNV-specific IgM was lowest in Iranians (0/77), Lebanese (0/108), and Filipinos (0/107) at 0.0%, and was highest in Sudanese at 10.0% (8/80). While there seemed to be apparent trends in the prevalence of WNV-IgM and WNV-IgG antibodies, none of these trends were found statistically significant. ConclusionThe findings support the circulation of WNV in human populations in the different countries of the MENA region. Seroprevalence was highest in Sudanese and Egyptians and lowest in Qataris and nationals of the Levant. The findings call for further animal, vector, and human studies, such as studying the actual prevalence of the viral RNA in blood donors to assess risk of viral transmission through blood donation and for a better characterization of the epidemiology of this infection in this part of the world. Qatar University internal grant (QUCG-CHS-19/20-1), Qatar National Research Fund (UREP20-020-3-003 and NPRP 9-040-3-008), and the Biomedical Research Program at Weill Cornell Medicine-Qatar.

In the present study, we serosurveyed the exposure of 222 draft horses to different arboviruses in the city of Santa Fe, Argentina. Plaque reduction neutralization tests confirmed exposure to Fort Sherman virus (FSV), Saint Louis encephalitis virus (SLEV), West Nile virus (WNV), and Rio Negro virus (RNV). Apparently, Western and Eastern equine encephalitis viruses did not circulate in the population tested. The confirmation of five seroconversions for WNV, FSV, and SLEV and the association between prevalence and age are indicative of recent circulation. These results highlight the importance of considering draft horses in arboviral surveillance in urban and rural areas of developing countries.

Purpose The primary objective of the study was to assess maternal and fetal outcomes of pregnancies affected with dengue fever. Methods This was a prospective, observational and descriptive study carried out over a period of 1 year. 216 pregnant women with fever were screened. Of these, 44 women tested positive for dengue (non-structural protein antigen 1 or dengue IgM antibodies in the sera). The clinical and laboratory characteristics of women with dengue were recorded. Maternal outcomes, pregnancy outcomes and fetal outcomes were studied. Results Mean period of gestation was 31.89 ± 7.31 weeks. Thrombocytopenia was seen in 23 (52.3%) women. Of 40 women, 10 (25%) developed post-partum haemorrhage. The incidence of maternal systemic complications was high: eight (18.2%) women developed acute kidney injury and two (4.5%) required haemodialysis support; eight (18.2%) women developed ARDS and seven (15.9%) women required ventilatory support; four (9.1%) women developed acute liver failure. 18 (40.9%) women had evidence of shock. Seven (15.9%) women died and another seven (15.9%) were classified as WHO maternal near-miss cases. Two (4.5%) pregnancies suffered from miscarriages, four (9%) from still births and two (4.5%) from neonatal deaths. Preterm babies were delivered in 15 (34.1%) and low birth weight babies in 13 (29.5%). Conclusions Dengue in pregnancy adversely affects maternal and fetal outcomes with high maternal mortality of 15.9%. Prematurity and postpartum haemorrhage are significant risks to mother and baby. Vector control strategies should be implemented with vigour in affected areas.

Inter-host transmission of pathogenic arboviruses such as dengue virus (DENV) and Zika virus (ZIKV) requires systemic infection of the mosquito vector. Successful systemic infection requires initial viral entry and proliferation in the midgut cells of the mosquito followed by dissemination to secondary tissues and eventual entry into salivary glands1. Lack of arbovirus proliferation in midgut cells has been observed in several Aedes aegypti strains2, but the midgut antiviral responses underlying this phenomenon are not yet fully understood. We report here that there is a rapid induction of apoptosis (RIA) in the Aedes aegypti midgut epithelium within 2 hours of infection with DENV-2 or ZIKV in both in vivo blood-feeding and ex vivo midgut infection models. Inhibition of RIA led to increased virus proliferation in the midgut, implicating RIA as an innate immune mechanism mediating midgut infection in this mosquito vector., Ayers et al. report rapid induction of apoptosis in the midgut of Aedes aegypti mosquitoes within 2 hours of infection by dengue and Zika viruses, and find that inhibiting apoptosis led to increased virus proliferation in the midgut. These results suggest rapid induction of apoptosis as an innate immune mechanism mediating midgut infection in this mosquito vector.

Zika virus (ZIKV) is an emerging arbovirus with recent global expansion. Historically, ZIKV infections with Asian lineages have been associated with mild disease such as rash and fever. However, recent Asian sub-lineages have caused outbreaks in the South Pacific and Latin America with increased prevalence of neurological disorders in infants and adults. Asian sub-lineage differences may partially explain the range of disease severity observed. However, the effect of Asian sub-lineage differences on pathogenesis remains poorly characterized. Current study conducts a head-to-head comparison of three Asian sub-lineages that are representative of the circulating ancestral mild Asian strain (ZIKV-SG), the 2007 epidemic French Polynesian strain (ZIKV-FP), and the 2013 epidemic Brazil strain (ZIKV-Brazil) in adult Cynomolgus macaques. Animals infected intervenously or subcutaneously with either of the three clinical isolates showed sub-lineage-specific differences in viral pathogenesis, early innate immune responses and systemic inflammation. Despite the lack of neurological symptoms in infected animals, the epidemiologically neurotropic ZIKV sub-lineages (ZIKV-Brazil and/or ZIKV-FP) were associated with more sustained viral replication, higher systemic inflammation (i.e. higher levels of TNFα, MCP-1, IL15 and G-CSF) and greater percentage of CD14+ monocytes and dendritic cells in blood. Multidimensional analysis showed clustering of ZIKV-SG away from ZIKV-Brazil and ZIKV-FP, further confirming sub-lineage differences in the measured parameters. These findings highlight greater systemic inflammation and monocyte recruitment as possible risk factors of adult ZIKV disease observed during the 2007 FP and 2013 Brazil epidemics. Future studies should explore the use of anti-inflammatory therapeutics as early treatment to prevent ZIKV-associated disease in adults.

We describe Shuni virus (SHUV) detection in human neurologic disease cases in South Africa. SHUV RNA was identified in 5% of cerebrospinal fluid specimens collected during the arbovirus season from public sector hospitals. This finding suggests that SHUV may be a previously unrecognized cause of human neurologic infections in Africa.

Objective To identify the arbovirus involved in febrile cases identified in a pediatric clinic in Cali, Valle del Cauca province, Colombia, and study the clinical characteristics. Methods A descriptive, prospective study enrolled 345 febrile children for 12 months in a pediatric clinic. Medical record registers documenting signs and symptoms, and serum samples were analyzed to detect DENV, CHIKV, and ZIKV by reverse transcription-polymerase chain reaction and serology methods. Diagnosis at the time of admission and discharge were compared based on laboratory test results. Results All patients were diagnosed as severe dengue at admission. Molecular detection and serology tests identified 143 CHIKV-positive (41.4%), 20 DENV-positive (5.8%), and 123 DENV-CHIKV coinfection patients (35.7%). DENV or CHIKV serology test results of these double-infected patients yield poor performance to confirm patient cases. ZIKV infection was detected in 5 patients (1.4%), every time as double or triple infections. Conclusion . A sustained CHIKV circulation and transmission was confirmed causing febrile illness in children and indicating that this virus spreads even during the regular DENV season, leading to double infections and altering clinical symptoms. Specific clinical tests are necessary to closely identify the arbovirus involved in causing infectious diseases that can help in better treatment and mosquito-transmitted virus surveillance.

A 56-year-old man receiving rituximab who had months of neurologic symptoms was found to have Jamestown Canyon virus in cerebrospinal fluid by clinical metagenomic sequencing. The patient died, and postmortem examination revealed extensive neuropathologic abnormalities. Deep sequencing enabled detailed characterization of viral genomes from the cerebrospinal fluid, cerebellum, and cerebral cortex.

ObjectiveTo describe frequency and clinical characteristics of MAYV infection in Piura, as well as the association of this pathogen with DENV.ResultsA total of 86/496 (17.3%) cases of MAYV were detected, of which 54 were MAYV mono-infection and 32 were co-infection with DENV, accounting for 10.9% and 6.4%, respectively. When evaluating monoinfection by MAYV the main groups were 18–39 and 40–59 years old, with 25.9% and 20.4% respectively. Co-infections were more common in the age group 18–39 and those > 60 years old, with 34.4% and 21.9%, respectively. The most frequent clinical presentation were headaches (94.4%, 51/54) followed by arthralgias (77.8%, 42/54). During the 8-month study period the most cases were identified in the months of May (29.1%) and June (50.0%).

West Nile virus (WNV) is the most prevalent arbovirus found throughout the United States. Surveillance of surface breeding Culex vectors involved in WNV transmission is primarily conducted using CDC Gravid traps. However, anecdotal claims from mosquito abatement districts in Louisiana assert that other trap types may be more suited to WNV surveillance. To test the validity of these assertions, we conducted a series of trapping trials and WNV surveillance over 3 yr to compare the efficacy of multiple trap types. First, we compared the CDC Gravid trap, CO2-baited New Standard Miniature Blacklight traps, and CO2-baited CDC light traps with either an incandescent light, a red light, or no light. We found that the CDC Gravid trap and CO2-baited no-light CDC Light trap collected the most mosquitoes. Second, we conducted additional, long-term trapping and WNV surveillance to compare these two trap types. We found that CO2-baited no-light CDC traps collected more of the local WNV vector, Culex quinquefasciatus (Say, Diptera, Culicidae), and detected WNV with greater sensitivity. Finally, we conducted trapping to compare the physiological states of Cx. quinquefasciatus and diversity of collected mosquitoes. CO2-baited no-light CDC light traps collected more unfed Cx. quinquefasciatus while Gravid traps collected more blooded Cx. quinquefasciatus; both traps collected the same number of gravid Cx. quinquefasciatus. Additionally, we found that CO2-baited no-light CDC light traps collected a larger diversity of mosquito species than Gravid traps.

The temperate United States has experienced increasing incidence of mosquito-borne diseases. Recent studies conducted in Baltimore, MD have demonstrated a negative relationship between abundances of Aedes albopictus (Skuse) and Culex mosquitoes and mean neighborhood income level, but have not looked at the presence of pathogens. Mosquitoes collected from five socioeconomically variable neighborhoods were tested for infection by West Nile, chikungunya, and Zika viruses in 2015 and 2016, and again from four of the neighborhoods in 2017. Minimum infection rates of pooled samples were compared among neighborhoods for each year, as well as among individual blocks in 2017. West Nile virus was detected in both Ae. albopictus and Culex pools from all neighborhoods sampled in 2015 and 2017. No infected pools were detected in any year for chikungunya or Zika viruses, and none of the target viruses were detected in 2016. Infection rates were consistently higher for Culex than for Ae. albopictus. Minimum infection rate was negatively associated with mean neighborhood income for both species in 2015. Although earlier work has shown a positive association between block-level abandonment and mosquito abundance, no association was detected in this study. Still, we demonstrate that viral infection in mosquito pools can differ substantially across adjacent urban neighborhoods that vary by income. Though trap security and accessibility often inform city sampling locations, detecting and managing arboviral risk requires surveillance across neighborhoods that vary in socioeconomics, including lower income areas that may be less accessible and secure but have higher infection rates.

Background Usutu virus (USUV) is a rapidly spreading zoonotic arbovirus (arthropod-borne virus) and a considerable threat to the global avifauna and in isolated cases to human health. It is maintained in an enzootic cycle involving ornithophilic mosquitoes as vectors and birds as reservoir hosts. Despite massive die-offs in wild bird populations and the detection of severe neurological symptoms in infected humans, little is known about which mosquito species are involved in the propagation of USUV. Methods In the present study, the vector competence of a German (i.e. “Central European”) and a Serbian (i.e. “Southern European”) Culex pipiens biotype molestus laboratory colony was experimentally evaluated. For comparative purposes, Culex torrentium, a frequent species in Northern Europe, and Aedes aegypti, a primarily tropical species, were also tested. Adult female mosquitoes were exposed to bovine blood spiked with USUV Africa 2 and subsequently incubated at 25 °C. After 2 to 3 weeks saliva was collected from each individual mosquito to assess the ability of a mosquito species to transmit USUV. Results Culex pipiens biotype molestus mosquitoes originating from Germany and the Republic of Serbia and Cx. torrentium mosquitoes from Germany proved competent for USUV, as indicated by harboring viable virus in their saliva 21 days post infection. By contrast, Ae. aegypti mosquitoes were relatively refractory to an USUV infection, exhibiting low infection rates and lacking virus in their saliva. Conclusions Consistent with the high prevalences and abundances of Cx. pipiens biotype molestus and Cx. torrentium in Central and Northern Europe, these two species have most likely played a historic role in the spread, maintenance, and introduction of USUV into Germany. Identification of the key USUV vectors enables the establishment and implementation of rigorous entomological surveillance programs and the development of effective, evidence-based vector control interventions. Graphical Abstract

West Nile Virus (WNV) is an arbovirus transmitted by mosquito bite involving birds as reservoirs, humans and equines as accidental hosts. Eight distinct lineages (WNV-1 to WNV-8) have been identified: WNV-1 and WNV-2 infect humans and animals, and WNV-3 to WNV-8 have been identified only in vectors. WNV has been implicated in neuroinvasives infections, especially meningitis and encephalitis. Tunisia experienced three epidemics in 1997, 2003 and 2012. Serological studies on humans, equines and birds as well as the detection of the virus in the vector favour a fairly frequent circulation in the country. A new epidemic has been observed in Tunisia between August and November 2018. The obtained sequences of the VWN from Tunisia 2018 grouped in a distinct monophyletic group within the Mediterranean subtype in Cluster 1, with a maximum of 2% nucleotide divergence. These sequences were clearly distinct from the Tunisia 1997, which grouped with sequences mainly from USA in Cluster 2. This work reports the genetic characterization of the Tunisia 2018 strain in comparison with the previously identified strains in Tunisia and worldwide. The epidemic virus Tunisia 2018 was genetically close to the Mediterranean basin and Eastern Europe sequences but distinct from the Tunisia 1997 closely related to the American sequences.

A novel arbovirus, called Schmallenberg virus (SBV), emerged in Europe in 2011 infecting domestic as well as wild ruminants. The virus was first detected in Poland during the 2012 vector season. In order to study the SBV post-epidemic period in Poland, over twenty-one thousand domestic ruminants (cattle, sheep, goats) were tested for SBV infection between 2013 and 2018. Samples were collected as part of the national Bluetongue virus (BTV) surveillance programme. Thirteen per cent of all samples were collected from animals between 6 months and one year of age. Overall, 37.5% of ruminants tested seropositive. The seroprevalence fluctuated yearly and was highest in 2014 and 2017; however, seroconversion was detected in younger animals throughout the study indicating continuous virus circulation during the 6-year study period. A significantly higher proportion of seropositive animals were detected among cattle and older animals. Uneven distribution of seropositive animals between provinces was identified and may be a result of different housing and breeding practices and/or meteorological conditions influencing local and regional vector abundances, rather than farm stocking densities. A small number of animals were identified as being exposed to both SBV and BTV; this is likely due to the fact that the same Culicoides species transmit these two viruses thus increasing the risk of co-exposure. Considering these results, in addition to virological and entomological studies carried out in Poland previously, it can be concluded that SBV is endemic in Poland with cyclical waves of virus circulation happening every 3-4 years.

Culicoides Latreille (Diptera: Ceratopogonidae) transmit arboviruses affecting wild and domestic ruminants such as bluetongue (BTV) and Schmallenberg virus (SBV). The sub-adult development and lifespan of Culicoides obsoletus s.s. (Meigen), Culicoides circumscriptus Kieffer and Culicoides paolae Boorman were examined at three different temperatures under laboratory conditions. Insects were collected from field between spring and autumn 2015 in two livestock farms located in Majorca (Spain). Gravid females were held individually at 18, 25 or 30 °C. Low temperatures increased the adult lifespan, time to oviposit and rate of development, whereas high temperatures increased the number of eggs, successful pupation and adult emergence as well as the larvae growth rate. The results showed that C. obsoletus s.s. have optimum development at 18 °C, whereas the optimal rearing temperature for C. circumscriptus and C. paolae was under warmer conditions of 25-30 °C. Variations in temperature/humidity and assays with different materials and substrates for oviposition should be considered in future studies. Understanding the requirements of the different species of Culicoides optimizing the results should be of special interest for predicting environmental change effects on these species, in addition to determining the rearing conditions for candidate Culicoides vectors.

Zika Virus (ZIKV), an arbovirus that belongs to the Flaviviridae family, has become a global concern since its outbreak in the Americas in 2015. With symptoms similar to other Flavivirus as Dengue and Yellow Fever viruses, infections by ZIKV have also been related to several neurological complications such as microcephaly in newborns and Guillain-Barre syndrome. Considering the high prevalence of ZIKV infection in certain areas, the risks that the virus poses to fetal brain development, and the fact that there is no vaccine or specific prophylaxis available, an effective treatment capable of preventing the infection is of potential interest. Therefore, in the present investigation, the antiviral activity on ZIKV of a group of xanthenodiones and intermediate ketones involved in their synthesis was evaluated for the first time. It was found that the compound 2-(2,6-dichlorobenzylidene)cyclohexane-1,3-dione 27 was able to completely inhibit the viral infection of Vero cells as well as to significantly reduce viral load in the brains of newborn Swiss mice. These effects are related to a direct interaction of the compound with the viral particle, blocking the viral adsorption.

Malaria is a longstanding public health problem in sub-Saharan Africa, while arthropod-borne viruses (arboviruses) like dengue and chikungunya cause an underrecognized burden of disease. While many human and environmental drivers affect the dynamics of vector-borne diseases, here we argue that the direct effects of warming temperatures are likely to promote greater environmental suitability for dengue and other arboviruses transmitted by Aedes aegypti while reducing the suitability for malaria transmitted by Anopheles gambiae. Environmentally-driven changes in disease dynamics will no doubt be complex and heterogeneous, but given that current public efforts are targeted to malaria control, we encourage the public health community to consider Aedes aeypgti and dengue, chikungunya, and other arboviruses as potential emerging public health threats in sub-Saharan Africa.

Background: The incidence and area of arbovirus infections is increasing around the world. It is largely linked to the spread of the main arbovirus vectors, invasive mosquito of the genus Aedes. Previously, it has been reported that Aedes aegypti reemerged in Russia after a 50-year absence. Moreover, in 2011, Ae. albopictus was registered in the city of Sochi (South Russia, Black Sea coast) for the first time. In 2013, Asian Ae. koreicus was found in Sochi for the first time. Methods: Mosquitoes were collected using the following methods: larvae with a dip net, imago on volunteers and using bait traps. The mosquitoes were identified using both morphology and sequencing of the second internal transcribed spacer of the nuclear ribosomal RNA gene cluster. Results: In August 2016, Ae. koreicus larvae and imago and a single male of Ae. aegypti were found on the southern coast of the Crimean Peninsula, where they were not registered before. Newly obtained DNA sequences were registered in GenBank with the accession numbers MF072936 and MF072937. Conclusion: Detection of invasive mosquito species (Ae. aegypti and Ae. koreicus) implies the possibility of their area expansion. Intensive surveillance is required at the Crimean Peninsula to evaluate the potential for the introduction of vector-borne diseases.

In 2017, the Institute of Tropical Medicine Pedro Kourí, University of Montreal Public Health Research Institute, and McGill University joined efforts to provide scenarios for scientific exchange and knowledge dissemination about the social science contribution on arboviral research. This commentary describes the scientific collaboration between Cuban and Canadian (Quebec) institutions, illustrating the need and opportunities to facilitate research and effective decision-making processes for arboviral prevention and control, going beyond traditional biomedical aspects. We organized a set of scientific activities within three international events conducted in Cuba between 2017 and 2018. Given the collaborating institutions’ expertise and the knowledge gaps in arboviral research, we selected three main thematic areas: social determinants and equity, community-based interventions and use of evidence for decision-making. The partnership shows that interdisciplinary collaboration and the use and integration of quantitative and qualitative methods from the social sciences is essential to face the current challenges in arbovirus research.

In 2015, the world witnessed the resurgence and global spread of Zika virus (ZIKV). This arbovirus infection is associated with Guillain-Barré syndrome in adults and with devastating congenital malformations during pregnancy. Despite scientific efforts, the development of a vaccine capable of inducing long-term protection has been challenging. Without a safe and efficacious licensed vaccine, control of virus transmission is based on vector control, but this strategy has been shown to be inefficient. An effective and protective vaccine relies on several requirements, which include: (i) induction of specific immune response against immunodominant antigens; (ii) selection of adjuvant-antigen formulation; and (iii) assessment of safety, effectiveness, and long-term protection. In this commentary, we provide a brief overview about the current efforts for the development of an efficacious ZIKV vaccine, covering the most important preclinical trials up to the formulations that are now being evaluated in clinical trials.

Ticks and mosquitoes are medically important vectors that transmit several pathogens, including arboviruses, to humans. Understanding how these blood-feeding arthropods transmit pathogens to humans requires knowledge on the molecular and cellular interplay at vector-host interface. Recent studies have highlighted the role of tick and mosquito small extracellular vesicles (EVs), including exosomes, facilitating arbovirus transmission within arthropod cells and from arthropod to mammalian cells. In this review, we summarize this emerging line of investigation in understanding the role of tick and mosquito exosomes in vector-pathogen-host tripartite interactions. Understanding the role of arthropod exosomes in pathogen interactions could lead to the discovery of novel therapeutic targets to interfere with the life cycle of several pathogens transmitted by vectors.

Spondweni virus (SPONV) is the most closely related known flavivirus to Zika virus (ZIKV). Its pathogenic potential and vector specificity have not been well defined. SPONV has been found predominantly in Africa, but was recently detected in a pool of Culex quinquefasciatus mosquitoes in Haiti. Here we show that SPONV can cause significant fetal harm, including demise, comparable to ZIKV, in a mouse model of vertical transmission. Following maternal inoculation, we detected infectious SPONV in placentas and fetuses, along with significant fetal and placental histopathology, together suggesting vertical transmission. To test vector competence, we exposed Aedes aegypti and Culex quinquefasciatus mosquitoes to SPONV-infected bloodmeals. Aedes aegypti could efficiently transmit SPONV, whereas Culex quinquefasciatus could not. Our results suggest that SPONV has the same features that made ZIKV a public health risk.

Viral diseases transmitted by mosquitoes, known as arboviruses, pose a significant threat to human life and are a major burden on many health systems around the world. Currently, arbovirus control strategies rely on insecticides or vector source reduction and, in the absence of effective, accessible and affordable vaccines, mainly on symptomatic based, non-specific treatments. However, insecticides have the potential to interfere with non-target organisms, cause environmental toxicity and insecticide resistance reduces their effectiveness as a sustainable control method. Complementary and sustainable strategies are urgently needed. Wolbachia, an invertebrate endosymbiont, has been used as an alternative strategy for arboviral control, through suppression or modification of mosquito populations. Here we discuss the burden that arboviruses impose on human populations and how Wolbachia can be used as a sustainable strategy for control, in alignment with the United Nations- 2030 Agenda for Sustainable Development.

Background St. Louis encephalitis virus (SLEV) is endemic and autochthonous on the American continent. Culex pipiens quinquefasciatus is a vector of SLEV; however, Culex interfor and Culex saltanensis have also been found to be naturally infected with SLEV. The aim of this study was to determine the vector competence of C. interfor and C. saltanensis for SLEV from Argentina compared with C. p. quinquefasciatus. Methods Female of the Culex species were orally infected by feeding on viraemic chicks that had been inoculated with SLEV. Abdomens, legs and saliva blood-fed mosquitoes were analysed by viral plaque assay. Results Mosquitoes were susceptible to orally acquired infection, dissemination and transmission of SLEV in the saliva. Conclusions Our results demonstrate that C. saltanensis and C. interfor are susceptible to SLEV and competent for its transmission.

Tick‐borne encephalitis virus (TBEV), a member of the family Flaviviridae, is the most important tick‐transmitted arbovirus in Europe. It can cause severe illnesses in humans and in various animal species. The main mechanism for the spread of TBEV into new areas is considered to be the translocation of infected ticks. To find out whether ducks can function as a natural virus reservoir in addition to serving as passive transport vectors, we carried out an experimental TBEV challenge study to reveal their susceptibility and resulting pathogenesis. Nineteen ducks were inoculated subcutaneously with TBEV strain “Neudoerfl” and monitored for 21 days. Blood, oropharyngeal and cloacal swabs were collected throughout the experiment and organ samples upon necropsy at the end of the study. All samples were tested for TBEV‐RNA by real‐time polymerase chain reaction. TBEV specific antibodies were determined by virus neutralization test and ELISA. Organ samples were examined histopathologically and by immunohistochemistry. The inoculated ducks did not show any clinical symptoms. TBEV‐specific RNA was detected in all brain samples as well as in a few blood and swab samples. Moreover, all challenged birds produced TBEV antibodies and showed a mild to severe acute to subacute necrotizing encephalitis. TBEV specific antigen was detected in the brain of 14 ducks by immunohistochemistry. The short and low viremic phases, as well as the low virus load in tissues suggest that ducks should not be considered as reservoir hosts. However, due to the high antibody levels, ducks can serve as sentinel species for the detection of natural TBEV foci.

Arthropod vectors serve as native reservoirs and transmitters of hundreds of arboviruses. In arthropod vectors, symbiotic microorganisms residing in the gut lumen and/or hemocoelic tissues maintain complicated relationships with their host and influence multiple aspects of vector physiology. Recently, accumulating evidence has established an important role for symbiotic microorganisms in vector-virus interactions which could potentially be used to control viral transmission. Herein, we review recent progress on symbiotic microbe-arbovirus interactions and summarize the molecular mechanisms by which commensal microbes act on hosts and arboviruses. Understanding the sophisticated interactions among arthropod vectors, microbiota, and arboviruses may offer new strategies for the prevention of arboviral diseases in the future.

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) in the genus Flavivirus and the Flaviviridae family. In 1947 and 1948 ZIKV was first isolated from a nonhuman primate as well as from mosquitoes in Africa, respectively. For half a century, ZIKV infections in human were sporadic prior to 2015–2016 pandemic spreading. Transmission of ZIKV from mother to fetus can occur in any trimester of pregnancy, even if mother was an asymptomatic carrier. The clinical signs of ZIKV infection are nonspecific and can be misdiagnosed as some other infectious diseases, especially those caused by arboviruses such as Dengue and Chikungunya. ZIKV infection was solely associated with mild illness prior to the large French Polynesian and Brazil outbreaks, when severe neurological complications, Guillain–Barre syndrome and dramatically increased rate of severe congenital malformations (including microcephaly) were reported. The adaptation of ZIKV to an urban cycle in endemic areas suggests that the incidence of ZIKV infections may be underestimated. The pandemic of novel coronavirus infection (COVID-19) demonstrates that lessons from ZIKV pandemic propagation has not been learned properly.

Rift Valley fever virus (RVFV) causes severe disease in domestic ungulates (cattle, goats, and sheep) and a febrile illness in humans (with ∼1% case fatality rate). This virus has been spreading geographically, and there is concern of it spreading to Europe or the Americas. Environmental temperature can significantly affect the ability of mosquitoes to transmit an arbovirus. However, these effects are not consistent among viruses or mosquito species. Therefore, we evaluated the effect of incubation temperatures ranging from 14°C to 30°C on infection and dissemination rates for Culex tarsalis and Aedes taeniorhynchus allowed to feed on hamsters infected with RVFV. Engorged mosquitoes were randomly allocated to cages and placed in incubators maintained at 14°C, 18°C, 22°C, 26°C, or 30°C. Although infection rates detected in Cx. tarsalis increased with increasing holding temperature, holding temperature had no effect on infection rates detected in Ae. taeniorhynchus. However, for both species, the percentage of mosquitoes with a disseminated infection after specific extrinsic incubation periods (4, 7, 10, 14, 17, or 21 days) increased with increasing incubation holding temperature, even after adjusting for the apparent increase in infection rate in Cx. tarsalis. The effects of environmental factors, such as ambient temperature, need to be taken into account when developing models for viral persistence and spread in nature.

The equine encephalitis viruses, Venezuelan (VEEV), East (EEEV) and West (WEEV), belong to the genus alphavirus, family Togaviridae and still represent a threat for human and animal public health in the Americas. In both, these infections are characterized by high viremia, rash, fever, encephalitis and death. VEEV encephalitis is similar, clinically, to other arboviral diseases, such as dengue, Zika or chikungunya. Most of the alphaviruses are transmitted between vertebrates and mosquitoes. They are able to replicate in a wide number of hosts, including mammals, birds, reptiles, amphibian and arthropods. The VEEV has enzootic and epizootic transmission cycles. At the enzootic one, enzootic strains (subtype I, serotypes D–F and serotypes II–VI) are continuously circulating between mosquitoes and wild rodents in tropical forests and mangroves of the Americas. The main reseroivrs are wild rodent species of the subfamily Sigmodontinae. However, bats can be also accidental reservoirs of VEEV. In this article, we reviewed the main features, epidemiology, clinical aspects and the current perspectives of the VEEV.

Background Solomon Islands, a country made up of tropical islands, has suffered cyclic dengue fever (DF) outbreaks in the past three decades. An outbreak of dengue-like illness (DLI) that occurred in April 2016 prompted this study, which aimed to determine the population’s immunity status and identify the arboviruses circulating in the country. Methods A household survey, involving 188 participants in two urban areas (Honiara and Gizo), and a parallel hospital-based clinical survey were conducted in April 2016. The latter was repeated in December after a surge in DLI cases. Arbovirus IgG ELISA were performed on the household blood samples to determine the prevalence of arboviruses in the community, while qPCR testing of the clinical samples was used to identify the circulating arboviruses. Dengue virus (DENV)-positive samples were further characterized by amplifying and sequencing the envelope gene. Results The overall prevalence rates of DENV, Zika virus, and chikungunya virus were 83.4%, 7.6%, and 0.9%, respectively. The qPCR positivity rates of the clinical samples collected in April 2016 were as follows: DENV 39.6%, Zika virus 16.7%, and chikungunya virus 6.3%, which increased to 74%, 48%, and 20% respectively in December 2016. The displacement of the circulating serotype-3, genotype-1, with DENV serotype 2, genotype cosmopolitan was responsible for the outbreak in 2016. Conclusions A DENV outbreak in Solomon Islands was caused by the introduction of a single serotype. The high prevalence of DENV provided transient cross-protection, which prevented the introduction of a new serotype from the hyperendemic region for at least 3 years. The severe outcomes seen in the recent outbreak probably resulted from changes in the causative viruses and the effects of population immunity and changes in the outbreak pattern. Solomon Islands needs to step up surveillance to include molecular tools, increase regional communication, and perform timely interventions.

Introduction:Usutu Virus (USUV) is a vector-borne flavivirus within the family of Flaviviridae; its reservoirs and vectors are birds and mosquitoes, respectively.Methods:At first, electronic databases were searched with a date range from 2000 to 2018 to find theCulexspecies that transmit the disease and then for determining the diversity of those, mosquito larvae were collected from six places in three main environmental categories using the dipping technique.Results:In total, 1369 specimens belonging to 10 different species were collected and identified, as follows:Cx. hortensisFicalbi,Cx. laticinctusEdwards,Cx. mimeticusNoe,Cx. perxigusTheobald,Cx. pipiensLinnaeus,Cx. modestusFicalbi,Cx. sinaiticusKirkpatrick,Cx. theileriTheobaldCx. torrentiumMartini andCx. tritaeniorhynchusGiles. Four species involved as vectors of USUV in other countries are printed in bold.Cx.pipiens,as the main vector was the most frequent species in rural areas, share its larval habitats withCx. torrentium(similarity > 0.9) and reached its peak in August. Overall, in the present study, there was a significant positive relationship between mean temperatures and abundance of mosquitoes (r = 0.75, P = 0.005).Conclusion:In the present study, some species involved as main vectors of USUV in other countries and their ecological features were recorded. Based on these results, the possibility of the emergence of USUV in Iran exists.

The complete coding sequences of five divergent strains of Changuinola virus (CGLV), collected over a 16-year period in Panama, were determined, using viral metagenomics. Each strain had 10 RNA segments that encoded structural and non-structural proteins with amino acid identities ranging from 33 to 99% with sequences of other 15 members of the Changuinola virus (Reoviridae: Orbivirus) species group. Genetic analyses of the five Panamanian virus strains revealed probable reassortment among multiple segments of the viruses.

The Aedes aegypti mosquito is the primary vector of dengue, yellow fever, chikungunya, and Zika viruses. Infection with the dengue virus alone occurs in an estimated 400 million people each year. Likelihood of infection with a virus transmitted by Ae. aegypti is most commonly attributed to abundance of the mosquito. However, the Arizona-Sonora desert region has abundant Ae. aegypti in most urban areas, yet local transmission of these arboviruses has not been reported in many of these cities. Previous work examined the role of differential Ae. aegypti longevity as a potential explanation for these discrepancies in transmission. To determine factors that were associated with Ae. aegypti longevity in the region, we collected eggs from ovitraps in Tucson, AZ and reared them under multiple experimental conditions in the laboratory to examine the relative impact of temperature and crowding during development, body size, fecundity, and relative humidity during the adult stage. Of the variables studied, we found that the combination of temperature during development, relative humidity, and body size produced the best model to explain variation in age at death. El mosquito Aedes aegypti es el vector primario de los virus de dengue, fiebre amarilla, chikungunya y Zika. Solamente las infecciones con los virus de dengue ocurren en aproximadamente 400 millones de personas cada año. La probabilidad de infección con un virus transmitido por Ae. aegypti es frecuentemente atribuido a la abundancia del mosquito. No obstante, la región del desierto de Arizona-Sonora tiene una abundancia de Ae. aegypti en la mayoría de las áreas urbanas, pero la transmisión local de estos arbovirus no ha sido reportada en muchas de estas ciudades. Trabajos previos han examinado el rol de las diferencias de longevidad en Ae. aegypti como explicación potencial por estas discrepancias en la transmisión. Para determinar que factores fueron asociados con longevidad en Ae. aegypti en la región, colectamos huevos de ovitrampas en Tucson, Arizona y los criamos debajo de múltiples condiciones experimentales en el laboratorio para examinar el impacto relativo de temperatura y competencia para nutrición durante desarrollo, tamaño del cuerpo, capacidad reproductiva, y humedad relativa durante adultez. De las variables estudiados, encontramos que la combinación de temperatura durante desarrollo, humedad relativa, y tamaño del cuerpo produjo el mejor modelo para explicar variación en edad al tiempo de la muerte.

El mosquito tigre es una especie invasora originaria del sudeste asiático que puede actuar como vector potencial de diversas arbovirosis como el dengue, el chikunguña y el zika. Desde el año 2004 en que se detectó por primera vez en España, se ha extendido por el litoral mediterráneo y otras áreas del interior peninsular, siguiendo una progresión que también se da en otras regiones de Europa y del mundo. En el mes de septiembre de 2018 se detectó su presencia en el municipio de Velilla de San Antonio (Comunidad de Madrid). Se estableció un grupo de trabajo entre salud pública, la Facultad de Ciencias Biológicas de la Universidad Complutense de Madrid y el ayuntamiento para definir y coordinar las actuaciones. Se establecieron dos áreas de trabajo, una de vigilancia, de 400-500 metros desde el punto en el que fue detectado y otra de actuación prioritaria, de 150-200 metros, con el objetivo de evaluar el área afectada, reducir su población e intentar su eliminación si ello fuera posible.

The fidelity of flaviviruses is thought to be tightly regulated for optimal fitness within and between hosts. West Nile virus (WNV) high-fidelity (HiFi) mutations V793I and G806R within the RNA-dependent RNA polymerase, and low-fidelity (LoFi) mutation T248I within the methyltransferase, were previously shown to attenuate infectivity and replicative fitness in Culex mosquitoes and Culex tarsalis (CXT) cells but not in mammalian cells. We hypothesized that fidelity alterations would modify adaptation and maintenance in a host-specific manner. To test this hypothesis, wild-type (WT), HiFi (V793I/G806R) and LoFi (T248I) variants were sequentially passaged eight times in avian (PDE) or mosquito cells, or alternately between the two. Initial characterization confirmed that fidelity mutants are attenuated in mosquito, but not avian, cells. Deep sequencing revealed mutations unique to both cell lines and fidelity mutants, including ENV G1378A, a mutation associated with avian cell adaptation. To characterize maintenance and adaptation, viral outputs were monitored throughout passaging and viral fitness was assessed. The results indicate that fidelity mutants can at times recover fitness during mosquito cell passage, but remain attenuated relative to WT. Despite similar initial fitness, LoFi mutants were impaired during sequential passage in avian cells. Conversely, HiFi mutants passaged in avian cells showed increased adaptation, suggesting that increased fidelity may be advantageous in avian hosts. Although some adaptation occurred with individual mutants, the output titres of fidelity mutants were on average lower and were often lost during host switching. These data confirm that arbovirus fidelity is likely fine-tuned to maximize survival in disparate hosts.