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The genus Orthobunyavirus is a diverse group of viruses in the family Peribunyaviridae, recently classified into 20 serogroups, and 103 virus species. Although most viruses within these serogroups are phylogenetically distinct, the absence of complete genome sequences has left several viruses incompletely characterized. Here we report the complete genome sequences for 11 orthobunyaviruses isolated from Trinidad, French Guiana, Guatemala, and Panama that were serologically classified into six serogroups and 10 species. Phylogenetic analyses of these 11 newly derived sequences indicate that viruses belonging to the Patois, Capim, Guama, and Group C serocomplexes all have a close genetic origin. We show that three of the 11 orthobunyaviruses characterized (belonging to the Group C and Bunyamwera serogroups) have evidence of histories of natural reassortment through the M genome segment. Our data also suggests that two distinct lineages of Group C viruses concurrently circulate in Trinidad and are transmitted by the same mosquito vectors. This study also highlights the importance of complementing serological identification with nucleotide sequencing when characterizing orthobunyaviruses.

Akabane virus (AKAV) is a teratogenic and neuropathogenic arbovirus that infects livestock and wild animals. AKAVs are endemic arboviruses from dairy farms in Taiwan in 1989, and the first sequence was detected in cattle with nonsuppurative encephalitis in 1992.This study aims to understand the epidemiological relationships of the akabane viruses between Taiwan and nearby places.In this study, 17 specimens were identified or isolated from vector insects, and ruminant fetuses collected from 1992 to 2015 were sequenced and analysed.Sequence analyses revealed all Taiwanese AKAVs belonged to genogroup Ia but diverged into two clusters in the phylogenetic trees, implying that at least two invasive events of AKAV may have occurred in Taiwan.The two clusters of AKAVs could still be identified in Taiwan in 2015, and a reassortment event was observed, indicating that the two clusters of AKAVs are already endemic in Taiwan.

Severe fever with thrombocytopenia syndrome (SFTS) caused by Dabie bandavirus (formerly SFTS virus, SFTSV), which belongs to the Bandavirus genus (formerly Phlebovirus genus) of the Phenuiviridae family (formerly Bunyaviridae family), is a tick-borne novel bunyavirus infection with high rates of mortality. SFTSV infection was diagnosed virologically in a 4-year-old dog with symptoms of lethargy and anorexia in western Japan in June 2017. The dog's owner, a man in his 40s, had taken care of the sick dog and became sick 10 days after disease onset in the dog, showing symptoms, such as fever, arthralgia, headache, nausea, and vomiting. Total blood cell counts revealed leukocytopenia and thrombocytopenia. He was treated as an outpatient. He had no scars suggesting that he had not been bitten by ticks. He was diagnosed as having SFTS via the detection of IgM and neutralizing antibodies to SFTSV. The patient was directly infected with SFTSV from the SFTSV-infected dog. In conclusion, humans can be at a risk of SFTSV infection through direct contact with sick dogs infected with SFTSV.

Schmallenberg orthobunyavirus (SBV), first discovered in 2011, belongs to the Orthobunyavirus genus of the Peribunyaviridae family. SBV, which predominantly infects ruminants, can cause severe fetal malformations when pregnant animals are infected during a critical phase of gestation. In this study, 1590 blood serum samples from cattle, sheep, and goats were obtained for serological investigation and 1604 specimens for virological investigation (including 1414 whole blood with EDTA, 165 vaginal swab samples from aborting animals, and tissue samples from 25 dead and/or aborted fetuses) in private and family-type ruminant establishments in Turkey's Eastern Mediterranean region. All the blood serum samples were tested for the presence of antibodies using ELISA, which showed SBV antibodies in 29.11% (95% CI: 26.89%-31.35%). The virological samples were tested using real-time RT-PCR for SBV nucleic acid presence, which showed 3.17% (95% CI:2.32%-4.04%) were positive. Finally, 10 different Culicoides species (a total of 29,156 Culicoides, including 16,005 females and 13,151 males) were tested to identify the vectors thought to carry infections in the region. However, no SBV nucleic acid was detected in the Culicoides pools.

Sand flies (Diptera: Phlebotominae) are proven vectors of various pathogens of medical and veterinary importance. Although mostly known for their pivotal role in the transmission of parasitic protists of the genus Leishmania that cause leishmaniases, they are also proven or suspected vectors of many arboviruses, some of which threaten human and animal health, causing disorders such as human encephalitis (Chandipura virus) or serious diseases of domestic animals (vesicular stomatitis viruses). We reviewed the literature to summarize the current published information on viruses detected in or isolated from phlebotomine sand flies, excluding the family Phenuiviridae with the genus Phlebovirus, as these have been well investigated and up-to-date reviews are available. Sand fly-borne viruses from four other families (Rhabdoviridae, Flaviviridae, Reoviridae and Peribunyaviridae) and one unclassified group (Negevirus) are reviewed for the first time regarding their distribution in nature, host and vector specificity, and potential natural transmission cycles.

Severe fever with thrombocytopenia syndrome (SFTS), a novel infectious disease caused by a novel bunyavirus and with a high case fatality rate (CFR), was reported by Chinese scientists in 2011. The causative virus, Dabie bandavirus also known as the SFTS virus (SFTSV), belongs to the genus Bandavirus (formerly named Phlebovirus) of the family Phenuiviridae (formerly named Bunyaviridae). SFTS was also reported to be endemic in South Korea and Japan in 2013. SFTSV circulates between some species of ticks and animals in nature. Humans are infected with SFTSV through bites from ticks such as Haemaphysalis longicornis and Amblyomma testidinarium. Domesticated animals, such as cats and dogs, are also infected with SFTSV and shown SFTS-like symptoms with a high CFR, likely having been infected through tick bites in the living environment. Furthermore, there have been cases of patients with SFTS who were infected with SFTSV through close contact with sick cats or dogs. The CFR in patients with SFTS is approximately 30% in Japan. There is always a risk of SFTSV infection in human populations living in endemic areas. Therefore, the development of specific therapies and vaccines is urgently needed to reduce the number of fatal SFTS cases.

Aphids are important agricultural pests, vectors of many plant viruses and have sophisticated relationships with symbiotic microorganisms. Abundant asymptomatic RNA viruses have been reported in aphids due to the application of RNA-seq, but aphid-virus interactions remain unclear. Bunyavirales is the most abundant RNA virus order, which can infect mammals, arthropods, and plants. However, many bunyaviruses have specific hosts, such as insects. Here, we discovered 18 viruses from 10 aphid species by RNA-seq. Importantly, a widespread presence bunyavirus, Aphid bunyavirus 1 (ABV-1), was determined to have a wide host range, infecting and replicating in all 10 tested aphid species. ABV-1 may be transmitted horizontally during feeding on plant leaves and vertically through reproduction. In a comparison of the physiological parameters of ABV-1

Peaton virus (PEAV) is a type of arthropod-borne virus (arbovirus) belonging to the genus Orthobunyavirus, much like Akabane virus and Aino virus. These arboviruses cause stillbirth and congenital malformations of fetuses in ruminants. In Japan, abnormal birth in bovine caused by PEAV were reported in Okinawa, Kyushu, and Chugoku regions, but it has never been reported in Shikoku region. The abnormal birth occurred in 2020 in Ehime Prefecture (Shikoku region) and suspected of being caused by PEAV from results of clinical signs, pathological findings, and virus neutralization test using PEAV. However, PEAV was not detected and isolated. This report describes the case of abnormal birth in bovine suspected of being caused by PEAV first occurred in Shikoku region, Japan.

Oropouche virus (OROV; genus Orthobunyavirus) is the etiological agent of Oropouche fever, a debilitating febrile illness common in South America. We used recombinant expression of the OROV M polyprotein, which encodes the surface glycoproteins Gn and Gc plus the nonstructural protein NSm, to probe the cellular determinants for OROV assembly and budding. Gn and Gc self-assemble and are secreted independently of NSm. Mature OROV Gn has two predicted transmembrane domains that are crucial for glycoprotein translocation to the Golgi complex and glycoprotein secretion, and unlike related orthobunyaviruses, both transmembrane domains are retained during Gn maturation. Disruption of Golgi function using the drugs brefeldin A and monensin inhibits glycoprotein secretion. Infection studies have previously shown that the cellular endosomal sorting complexes required for transport (ESCRT) machinery is recruited to Golgi membranes during OROV assembly and that ESCRT activity is required for virus secretion. A dominant-negative form of the ESCRT-associated ATPase VPS4 significantly reduces recombinant OROV glycoprotein secretion and blocks virus release from infected cells, and VPS4 partly colocalizes with OROV glycoproteins and membranes costained with Golgi markers. Furthermore, immunoprecipitation and fluorescence microscopy experiments demonstrate that OROV glycoproteins interact with the ESCRT-III component CHMP6, with overexpression of a dominant-negative form of CHMP6 significantly reducing OROV glycoprotein secretion. Taken together, our data highlight differences in M polyprotein processing across orthobunyaviruses, indicate that Golgi and ESCRT function are required for glycoprotein secretion, and identify CHMP6 as an ESCRT-III component that interacts with OROV glycoproteins. IMPORTANCE Oropouche virus causes Oropouche fever, a debilitating illness common in South America that is characterized by high fever, headache, myalgia, and vomiting. The tripartite genome of this zoonotic virus is capable of reassortment, and there have been multiple epidemics of Oropouche fever in South America over the last 50 years, making Oropouche virus infection a significant threat to public health. However, the molecular characteristics of this arbovirus are poorly understood. We developed a recombinant protein expression system to investigate the cellular determinants of OROV glycoprotein maturation and secretion. We show that the proteolytic processing of the M polypeptide, which encodes the surface glycoproteins (Gn and Gc) plus a nonstructural protein (NSm), differs between OROV and its close relative Bunyamwera virus. Furthermore, we demonstrate that OROV M glycoprotein secretion requires the cellular endosomal sorting complexes required for transport (ESCRT) membrane-remodeling machinery and identify that the OROV glycoproteins interact with the ESCRT protein CHMP6.

Bunyaviruses cleave host cellular mRNAs to acquire cap structures for their own mRNAs in a process called cap-snatching. How bunyaviruses interact with cellular mRNA surveillance pathways such as nonsense-mediated decay (NMD) during cap-snatching remains poorly understood, especially in plants. Rice stripe virus (RSV) is a plant bunyavirus threatening rice production in East Asia. Here, with a newly developed system allowing us to present defined mRNAs to RSV in Nicotiana benthamiana, we found that the frequency of RSV to target nonsense mRNAs (nsRNAs) during cap-snatching was much lower than its frequency to target normal mRNAs. The frequency of RSV to target nsRNAs was increased by virus-induced gene silencing of UPF1 or SMG7, each encoding a protein component involved in early steps of NMD (in an rdr6 RNAi background). Coincidently, RSV accumulation was increased in the UPF1- or SMG7-silenced plants. These data indicated that the frequency of RSV to target nsRNAs during cap-snatching is restricted by NMD. By restricting the frequency of RSV to target nsRNAs, NMD may impose a constraint to the overall cap-snatching efficiency of RSV. Besides a deeper understanding for the cap-snatching of RSV, these findings point to a novel role of NMD in plant-bunyavirus interactions.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging negatively stranded enveloped RNA bunyavirus that causes SFTS with a high case fatality rate of up to 30%. Macroautophagy/autophagy is an evolutionarily conserved process involved in the maintenance of host homeostasis, which exhibits anti-viral or pro-viral responses in reaction to different viral challenges. However, the interaction between the bunyavirus SFTSV and the autophagic process is still largely unclear. By establishing various autophagy-deficient cell lines, we found that SFTSV triggered RB1CC1/FIP200-BECN1-ATG5-dependent classical autophagy flux. SFTSV nucleoprotein induced BECN1-dependent autophagy by disrupting the BECN1-BCL2 association. Importantly, SFTSV utilized autophagy for the viral life cycle, which not only assembled in autophagosomes derived from the ERGIC and Golgi complex, but also utilized autophagic vesicles for exocytosis. Taken together, our results suggest a novel virus-autophagy interaction model in which bunyavirus SFTSV induces classical autophagy flux for viral assembly and egress processes, suggesting that autophagy inhibition may be a novel therapy for treating or releasing SFTS.

La Crosse virus (LACV) is a mosquito-borne orthobunyavirus that causes approximately 60 to 80 hospitalized pediatric encephalitis cases in the United States yearly. The primary treatment for most viral encephalitis, including LACV, is palliative care, and specific antiviral therapeutics are needed. We screened the National Center for Advancing Translational Sciences library of 3,833 FDA-approved and bioactive small molecules for the ability to inhibit LACV-induced death in SH-SY5Y neuronal cells. The top three hits from the initial screen were validated by examining their ability to inhibit virus-induced cell death in multiple neuronal cell lines. Rottlerin consistently reduced LACV-induced death by 50% in multiple human and mouse neuronal cell lines with an effective concentration of 0.16–0.69 µg ml−1 depending on cell line. Rottlerin was effective up to 12 hours post-infection in vitro and inhibited virus particle trafficking from the Golgi apparatus to trans-Golgi vesicles. In human inducible pluripotent stem cell-derived cerebral organoids, rottlerin reduced virus production by one log and cell death by 35% compared with dimethyl sulfoxide-treated controls. Administration of rottlerin in mice by intraperitoneal or intracranial routes starting at 3 days post-infection decreased disease development by 30–50%. Furthermore, rottlerin also inhibited virus replication of other pathogenic California serogroup orthobunyaviruses (Jamestown Canyon and Tahyna virus) in neuronal cell lines. Viral encephalitis caused in mice by La Crosse arbovirus can be treated with rottlerin, which prevents viral trafficking from the Golgi and reduces virus titres and neuronal cell death in the central nervous system.

The circulation of arboviruses in livestock ruminants has often gone unrecognized owing to the fact that a significant percentage of arboviruses probably induce subclinical infections and/or negligible symptoms in infected animals. To determine the current situation of arbovirus circulation in the Yaeyama Islands, attempts to isolate viruses from bovine blood samples collected between 2014 and 2019 have been made. In total, 308 blood samples were collected during the study period, and 43 of them induced cytopathic effects (CPEs) in cell cultures. The identification of the CPE agents was performed by reported RT-PCR assays and a high-throughput analysis with a next-generation sequencing platform. The obtained viruses consisted of an orthobunyavirus (Peaton virus), Culicoides-borne orbiviruses (bluetongue virus serotypes 12 and 16, epizootic hemorrhagic disease virus [EHDV] serotypes 5, 6, and 7, D'Aguilar virus, and Bunyip Creek virus), and potential mosquito-borne orbiviruses (Yunnan orbivirus, Guangxi orbivirus, and Yonaguni orbivirus). Most of the orbiviruses were recovered from washed blood cells with mosquito cell cultures, suggesting that this combination was more efficient than other combinations such as plasma/blood cells and hamster cell lines. This marked the first time that the isolation of EHDV serotypes 5 and 6 and three potential mosquito-borne orbiviruses was recorded in Japan, showing a greater variety of orbiviruses on the islands than previously known. Genetic analysis of the isolated orbiviruses suggested that the Yaeyama Islands and its neighboring regions were epidemiologically related. Some of the viruses, especially the potential mosquito-borne orbiviruses, were isolated during several consecutive years, indicating their establishment on the islands.

Ixodid ticks represent vectors and reservoirs for a broad range of zoonotic pathogens. Collected ticks from field studies are therefore usually stored in ethanol, which in higher concentrations effectively inactivates most of the known tick-borne pathogens. Although commonly practiced as gold standard for inactivation, hardly any scientific data demonstrate that ethanol sufficiently penetrates the comparatively thick cuticula of ticks. Therefore, Amblyomma hebraeum tick pools were stored for 21 days in ethanol (96%). Afterwards, the ethanol was removed and the ticks were homogenized. Quantitative 1H-NMR spectroscopic analysis was applied to determine the residual concentration of ethanol inside the ticks. 1H-NMR spectroscopic analysis revealed that ethanol constituted 28.3–42.6 mg of the total weight of three ticks in the pools (89.9–121.5 mg). In addition, the low-pathogenic Hazara orthonairovirus (HAZV) was used as a cell culture model for this study. The virus was exposed to ethanol concentrations between 0 and 60% and incubated under various temperature conditions for four time periods. Afterwards, the residual virus infectivity was determined by titration. Following ethanol exposure, HAZV did not grow in cells after 9 h of exposure to an ethanol concentration of 25%. These results demonstrate an extremely low ethanol resistance of the virus, which was generally in line with previously reported ethanol inactivation data for Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV). After prolonged storage and impregnation, comparable ethanol concentrations are achieved in the ticks, indicating the suitability of this inactivation method also for Bunyaviruses in ticks. At the very least, a massive virus inactivation can be assumed. Definitive proof of virus inactivation would require a bioassay of ethanol-treated infected ticks under appropriate biosafety conditions.

Bunyaviruses represent the largest group of RNA viruses and are the causative agent of a variety of febrile and hemorrhagic illnesses. Originally characterized as a single serotype in Africa, the number of described bunyaviruses now exceeds over 500, with its presence detected around the world. These predominantly tri-segmented, single-stranded RNA viruses are transmitted primarily through arthropod and rodent vectors and can infect a wide variety of animals and plants. Although encoding for a small number of proteins, these viruses can inflict potentially fatal disease outcomes and have even developed strategies to suppress the innate antiviral immune mechanisms of the infected host. This short review will attempt to provide an overall description of the order Bunyavirales, describing the mechanisms behind their infection, replication, and their evasion of the host immune response. Furthermore, the historical context of these viruses will be presented, starting from their original discovery almost 80 years ago to the most recent research pertaining to viral replication and host immune response.

We discuss genomic detection of Schmallenberg virus in both Culicoides midges and affected ruminants during June 2018–December 2019, demonstrating its circulation in Israel. This region is a geographic bridge between 3 continents and may serve as an epidemiologic bridge for potential Schmallenberg virus spread into Asia.

Tick infestations have been reported as one of the factors threatening the health of giant pandas, but studies of viral pathogens carried by ticks feeding on the blood of giant pandas are limited. To assess whether blood-sucking ticks of giant pandas can carry viral pathogens and if so, whether the viruses in ticks are associated with those previously detected in giant panda hosts, we determined the viromes of ticks detached from giant pandas in a field stocking area in Sichuan Province, southwest China. Using viral metagenomics we identified 32 viral species in ticks, half of which (including anellovirus [

Viral hemorrhagic fevers caused by members of the order Bunyavirales comprise endemic and emerging human infections that are significant public health concerns. Despite the disease severity, there are few therapeutic options available, and therefore effective antiviral drugs are urgently needed to reduce disease burdens. Bunyaviruses, like influenza viruses (IFVs), possess a cap-dependent endonuclease (CEN) that mediates the critical cap-snatching step of viral RNA transcription. We screened compounds from our CEN inhibitor (CENi) library and identified specific structural compounds that are 100 to 1,000 times more active in vitro than ribavirin against bunyaviruses, including Lassa virus, lymphocytic choriomeningitis virus (LCMV), and Junin virus. To investigate their inhibitory mechanism of action, drug-resistant viruses were selected in culture. Whole-genome sequencing revealed that amino acid substitutions in the CEN region of drug-resistant viruses were located in similar positions as those of the CEN α3-helix loop of IFVs derived under drug selection. Thus, our studies suggest that CENi compounds inhibit both bunyavirus and IFV replication in a mechanistically similar manner. Structural analysis revealed that the side chain of the carboxyl group at the seventh position of the main structure of the compound was essential for the high antiviral activity against bunyaviruses. In LCMV-infected mice, the compounds significantly decreased blood viral load, suppressed symptoms such as thrombocytopenia and hepatic dysfunction, and improved survival rates. These data suggest a potential broad-spectrum clinical utility of CENis for the treatment of both severe influenza and hemorrhagic diseases caused by bunyaviruses.

Oropouche orthobunyavirus (OROV; Peribunyaviridae ) is a mosquito-transmitted virus that causes widespread human febrile illness in South America, with occasional progression to neurologic effects. Host factors mediating the cellular entry of OROV are undefined. Here, we show that OROV uses the host protein low-density lipoprotein–related protein 1 (Lrp1) for efficient cellular infection. Cells from evolutionarily distinct species lacking Lrp1 were less permissive to OROV infection than cells with Lrp1. Treatment of cells with either the high-affinity Lrp1 ligand receptor-associated protein (RAP) or recombinant ectodomain truncations of Lrp1 significantly reduced OROV infection. In addition, chimeric vesicular stomatitis virus (VSV) expressing OROV glycoproteins (VSV-OROV) bound to the Lrp1 ectodomain in vitro. Furthermore, we demonstrate the biological relevance of the OROV-Lrp1 interaction in a proof-of-concept mouse study in which treatment of mice with RAP at the time of infection reduced tissue viral load and promoted survival from an otherwise lethal infection. These results with OROV, along with the recent finding of Lrp1 as an entry factor for Rift Valley fever virus, highlight the broader significance of Lrp1 in cellular infection by diverse bunyaviruses. Shared strategies for entry, such as the critical function of Lrp1 defined here, provide a foundation for the development of pan-bunyaviral therapeutics.

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.

Sera from white-tailed deer (WTD, Odocoileus virginianus) hunter-harvested throughout New York State (NYS), 2007–2015, were tested by plaque reduction neutralization for antibodies against nine mosquito-borne viruses from the families Peribunyaviridae, Flaviviridae, and Togaviridae. Overall, 76.1% (373/490) of sampled WTD were seropositive against at least one virus, and 38.8% were exposed to multiple viruses. The seropositivity rate in adult WTD (78.0%) was significantly greater (P < 0.0001) than that in fawns (47.7%). Neutralizing antibodies against California serogroup viruses were most common in WTD sampled across all regions (67.1%), followed by the Bunyamwera serogroup (BUN) (37.6%). Jamestown Canyon and Cache Valley orthobunyaviruses were responsible for most California and BUN infections, respectively. Seroprevalence rates to West Nile virus were higher in samples originating from Long Island (LI) (19.0%) than in those originating from the central (7.3%), western (5.0%), and Hudson Valley (4.4%) regions of NYS. Antibodies to Eastern equine encephalitis virus were seen primarily in WTD from central NYS (5.1%), where annual enzootic activity occurs, but low rates were documented in western NYS (1.4%) and LI (1.7%). Low rates of Potosi and LaCrosse orthobunyavirus, and Highlands J virus antibodies were detected over the course of this investigation. St. Louis encephalitis virus (or a closely related virus) antibodies were detected in samples collected from central and western NYS, suggesting local virus transmission despite a lack of evidence from routine mosquito surveillance. Serologic results demonstrate the value of WTD in NYS as an indicator of arbovirus distribution and recent transmission on a relatively fine spatial scale.

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.

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.

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.

Schmallenberg disease (SBD) is an emerging vector‐borne disease that affects domestic and wild ruminants. A long‐term serosurvey was conducted to assess exposure to Schmallenberg virus (SBV) in all the wild ruminant species present in mainland Spain. Between 2010 and 2016, sera from 1,216 animals were tested for antibodies against SBV using a commercial blocking ELISA. The overall prevalence of antibodies was 27.1% (95%CI: 24.7–29.7). Statistically significant differences among species were observed, with significantly higher seropositivity found in fallow deer (Dama dama) (45.6%; 99/217), red deer (Cervus elaphus) (31.6%; 97/307) and mouflon (Ovis aries musimon) (28.0%; 33/118) compared to Barbary sheep (Ammotragus lervia) (22.2%; 8/36), Iberian wild goat (Capra pyrenaica) (19.9%; 49/246), roe deer (Capreolus capreolus) (17.5%; 34/194) and Southern chamois (Rupicapra pyrenaica) (10.2%; 10/98). Seropositive animals were detected in 81.4% (57/70; 95%CI: 70.8–88.8) of the sampled populations. SBV seroprevalence ranged from 18.8% (48/256) in bioregion (BR)2 (north‐central, Mediterranean) to 32.3% (31/96) in BR1 (northeastern or Atlantic, Eurosiberian). Anti‐SBV antibodies were not found before 2012, when the first outbreak of SBD was reported in Spain. In contrast, seropositivity was detected uninterruptedly during the period 2012–2016 and anti‐SBV antibodies were found in yearling animals in each of these years. Our results provide evidence of widespread endemic circulation of SBV among wild ruminant populations in mainland Spain in recent years. Surveillance in these species could be a useful tool for monitoring SBV in Europe, particularly in areas where wild ruminants share habitats with livestock., This work has benefited from the financial aid of research grants funded by Spanish Ministry of Economy and Competitiveness (AGL2013‐49159‐C2‐2‐R, AGL2016‐76358‐R and CGL2017‐89866‐R). S. Jiménez‐Ruiz holds a PhD contract from the UCLM co‐supported by the European Social Fund (2018/12504).

In common with all segmented negative-sense RNA viruses, bunyavirus transcripts contain heterologous sequences at their 5' termini originating from capped host cell RNAs. These heterologous sequences are acquired by a so-called cap-snatching mechanism. Whereas for nuclear replicating influenza virus the source of capped primers as well as the cap-binding and endonuclease activities of the viral polymerase needed for cap snatching have been functionally and structurally well characterized, our knowledge on the expected counterparts of cytoplasmic replicating bunyaviruses is still limited and controversial. This review focuses on the cap-snatching mechanism of bunyaviruses in the light of recent structural and functional data.

An epizootic caused by a new orthobunyavirus called Schmallenberg virus (SBV) was recognised in European ruminants in 2011 and 2012. The re-emergence of the infection was reported in several countries in the subsequent years. Although the main clinical sign of SBV infection is abortion, the impact of SBV in natural cases of abortion in domestic ruminants had not been systematically examined before this study. The aim of the study was to investigate the role of SBV infection and to compare it to the importance of other causes of abortion by examining 537 natural cases of abortion that had occurred between 2011 and 2017 in Hungary. The cause of abortion was determined in 165 (31%) cases. An infectious cause was proved in 88 (16%) cases. SBV infection was found only in a total of four cases (0.8%) using real-time polymerase chain reaction. Three of them proved to be inapparent SBV infection, and one case was attributed to SBV-induced abortion by detecting non-purulent encephalitis and SBV nucleoprotein by immunohistochemistry in a brain tissue sample. According to the results, SBV played a minor role in natural cases of domestic ruminant abortion in Hungary during the 7-year period following the first SBV outbreak in 2011.

The viruses historically implicated or currently considered as candidates for misuse in bioterrorist events are poxviruses, filoviruses, bunyaviruses, orthomyxoviruses, paramyxoviruses and a number of arboviruses causing encephalitis, including alpha- and flaviviruses. All these viruses are of concern for public health services when they occur in natural outbreaks or emerge in unvaccinated populations. Recent events and intelligence reports point to a growing risk of dangerous biological agents being used for nefarious purposes. Public health responses effective in natural outbreaks of infectious disease may not be sufficient to deal with the severe consequences of a deliberate release of such agents. One important aspect of countermeasures against viral biothreat agents are the antiviral treatment options available for use in post-exposure prophylaxis. These issues were adressed by the organizers of the 16th Medical Biodefense Conference, held in Munich in 2018, in a special session on the development of drugs to treat infections with viruses currently perceived as a threat to societies or associated with a potential for misuse as biothreat agents. This review will outline the state-of-the-art methods in antivirals research discussed and provide an overview of antiviral compounds in the pipeline that are already approved for use or still under development.

Akabane virus (AKAV), belonging to the genus Orthobunyavirus and family Peribunyaviridae, causes reproductive and congenital abnormalities in ruminants. Its envelope glycoprotein Gc is a neutralizing antigen, on which at least five distinct antigenic regions have been identified. We attempted to identify the domains using truncated recombinant AKAV Gc proteins expressed in Escherichia coli and monoclonal antibodies (mAbs) with AKAV-neutralizing activity. Dot blot analysis revealed that amino acid positions 1-97 and 189-397 (Gc

Bats are reservoirs of important zoonotic viruses like Nipah and SARS viruses. However, whether the blood-sucking arthropods on the body surface of bats also carry these viruses and the relationship between viruses carried by the blood-sucking arthropods and viruses carried by bats have not been reported. This study collected 686 blood-sucking arthropods on the body surface of bats from Yunnan Province, China, between 2012 and 2015, and they included wingless bat flies, bat flies, ticks, mites, and fleas. The viruses carried by these arthropods were analyzed using a meta-transcriptomic approach, and 144 highly diverse positive-sense single-stranded RNA, negative-sense single-stranded RNA, and double-stranded RNA viruses were found, of which 138 were potentially new viruses. These viruses were classified into 14 different virus families or orders, including Bunyavirales, Mononegavirales, Reoviridae, and Picornavirales. Further analyses found that Bunyavirales were the most abundant virus group (84% of total virus RNA) in ticks, whereas narnaviruses were the most abundant (52 to 92%) in the bat flies and wingless bat flies libraries, followed by solemoviruses (1 to 29%) and reoviruses (0 to 43%). These viruses were highly structured based on the arthropod types. It is worth noting that no bat-borne zoonotic viruses were found in the virome of bat-infesting arthropod, seemingly not supporting that bat surface arthropods are vectors of zoonotic viruses carried by bats. IMPORTANCE Bats are reservoirs of many important viral pathogens. To evaluate whether bat-parasitic blood-sucking arthropods participate in the circulation of these important viruses, it is necessary to conduct unbiased virome studies on these arthropods. We evaluated five types of blood-sucking parasitic arthropods on the surface of bats in Yunnan, China, and identified a variety of viruses, some of which had high prevalence and abundance levels, although there is limited overlap in virome between distant arthropods. While most of the virome discovered here is potentially arthropod-specific viruses, we identified three possible arboviruses, including one orthobunyavirus and two vesiculoviruses (family Rhabdoviridae), suggesting bat-parasitic arthropods carry viruses with risk of spillage, which warrants further study.

The global impact of mosquito-borne diseases has increased significantly over recent decades. Ebinur Lake virus (EBIV), a newly classified orthobunyavirus, is reported to be highly pathogenic in adult mice. The evaluation of vector competence is essential for predicting the arbovirus transmission risk. Here, Aedes aegypti was applied to evaluate EBIV infection and dissemination in mosquitos. Our experiments indicated that Ae. aegypti had the possibility to spread EBIV (with a transmission rate of up to 11.8% at 14 days post-infection) through biting, with the highest viral dose in a single mosquito’s saliva reaching 6.3 plaque-forming units. The highest infection, dissemination and ovary infection rates were 70%, 42.9%, and 29.4%, respectively. The high viral infection rates in Ae. aegypti ovaries imply the possibility of EBIV vertical transmission. Ae. aegypti was highly susceptible to intrathoracic infection and the saliva-positive rate reached 90% at 10 days post-infection. Transcriptomic analysis revealed Toll and Imd signaling pathways were implicated in the mosquito’s defensive response to EBIV infection. Defensin C and chitinase 10 were continuously downregulated in mosquitoes infected via intrathoracic inoculation of EBIV. Comprehensive analysis of the vector competence of Ae. aegypti for EBIV in laboratory has indicated the potential risk of EBIV transmission through mosquitoes. Moreover, our findings support a complex interplay between EBIV and the immune system of mosquito, which could affect its vector competence.

Tamdy virus (TAMV) is an emerging zoonotic tick-borne arbovirus in the genus Orthonairovirus. Reports of human infections with TAMV have been increasing and development of a rapid detection assay is thus urgently required. In the present study, singleplex and dual-target real-time reverse transcription PCR (qRT-PCR) assays were established for the detection of TAMV. Sensitivity and specificity were evaluated, which demonstrated high sensitivity for both the singleplex and dual-target qRT-PCR assays with no cross-reaction with common bunyaviruses and tick-borne viruses. The TaqMan-based qRT-PCR methodology established in this study can be employed for epidemiological surveillance and pathogenesis studies of TAMV.

Akabane virus (AKAV) is an etiological agent that is teratogenic to the fetus of domestic ruminants, causing a significant loss of reproduction in livestock. In East Asia, AKAV isolates form two major clusters: genogroups I and II. In recent years, genogroup I isolates have also been associated with postnatal encephalomyelitis, mainly in calves. Here, we compared the pathogenicity in mice using genogroup I Iriki and genogroup II OBE-1 strains. Only mice infected intraperitoneally with the Iriki strain died and showed marked replication in the central nervous system (CNS) and lymphoid tissues. A more elevated blood-brain barrier (BBB) permeability was found in the Iriki-infected mice in the clinical phase, indicating that the BBB might be a possible route of viral transmission from the periphery to the CNS. These findings demonstrate that the Iriki strain presents greater neurovirulence and neuroinvasiveness compared with the OBE-1 strain, determining different AKAV pathogenicity among genogroups.

The cap-snatching endonuclease (EN) of segmented negative-strand RNA viruses (sNSVs) produces short capped primers for viral transcription by cleaving the host mRNAs. EN requires divalent metals as cofactors for nucleic acid substrates cleavage; however, the detailed mechanism of metal ion-dependent catalysis of ENs remains obscure. In this work, we reported the EN crystal structure of the Ebinur Lake virus (EBIV), an emerging mosquito-borne orthobunyavirus, and investigated its enzymatic properties and metal ion-based catalytic mechanism. In vitro biochemical data showed that EBIV EN is a specific RNA nuclease and prefers to cleave unstructured uridine-rich ssRNA. Structural comparison indicated that the overall structural architecture of EBIV EN is similar to that of other sNSV ENs, while the detailed active site configuration including the binding state of metal ions and the conformation of the LA/LB loop pair is different. Based on sequence conservation analysis, nine active site mutants were constructed, and seven crystal structures of them were determined. Mutations of active site residues associated with the two metal ions (Mn1 and Mn2) coordination abolished EN activity. Crystallographic analyses further revealed that none of these mutants bound two metal ions simultaneously in the active site. Importantly, we found that the perturbation of Mn1-coordination (metal site 1), resulted in the enhancement or elimination of Mn2-coordination (metal site 2). Taken together, our data provide structural evidence to support the two-metal-ion catalytic mechanism of EBIV EN and the correlation of metal binding at the two binding sites, which may be commonly shared by bunyaviruses or other sNSVs. IMPORTANCE The viral endonucleases (ENs) encoded by bunyaviruses and orthomyxoviruses play an essential role in initiating transcription by “snatching” capped primers from the host mRNAs. These ENs are metal-ion-dependent nucleases; however, the details of their catalytic mechanism remain elusive. Here, we reported high-resolution crystal structures of the wild-type and mutant ENs of a novel bunyavirus, the Ebinur Lake virus (EBIV), and revealed the structure and function relationship of EN. The EBIV EN exhibited differences in the details of active site structure compared to its homologues. Our data provided structural evidence to support a two-metal-ion catalytic mechanism of EBIV EN, and found the correlation of metal binding at both binding sites, which might reflect the dynamic structural properties that correlate to EN catalytic function. Taken together, our results revealed the structural characteristics of EBIV EN and made important implications for understanding the catalytic mechanism of cap-snatching ENs.

Schmallenberg virus (SBV—Orthobunyavirus serogroup Simbu) is an emerging RNA vector-borne virus which has an important impact in animal health within Europe, and some Asian and African countries. It is mainly reported in ruminants, causing congenital malformations and stillbirths. However, there are no studies regarding the occurrence, diagnosis, or surveillance of SBV in Brazil, due to the lack of diagnostic techniques available so far. This study aimed to implement a reliable diagnostic technique able to detect the SBV in Brazil and also to investigate occurrence of the virus in this country. A molecular technique, quantitative reverse transcription polymerase chain reaction (RT-qPCR), was used to analyze 1665 bovine blood samples and 313 aborted fetuses, as well as 596 serum samples were analyzed by serological analysis. None of the blood and fetus samples analyzed was positive for SBV, and neither serum samples were reactive for antibodies anti-SBV. Thus, although Brazil presents suitable conditions for the dissemination of the SBV, results of the present study suggest that SBV did not propagate in the analyzed bovine population. Supplementary Information The online version contains supplementary material available at 10.1007/s42770-021-00637-6.

In the last decade and a half, emerging vector-borne diseases have become a substantial threat to cattle across Europe. To mitigate the impact of the emergence of new diseases, outbreaks must be detected early. However, the clinical signs associated with many diseases may be nonspecific. Furthermore, there is often a delay in the development of new diagnostic tests for novel pathogens which limits the ability to detect emerging disease in the initial stages. Syndromic Surveillance has been proposed as an additional surveillance method that could augment traditional methods by detecting aberrations in non-specific disease indicators. The aim of this study was to develop a syndromic surveillance system for Irish dairy herds based on routinely collected milk recording and meteorological data. We sought to determine whether the system would have detected the 2012 Schmallenberg virus (SBV) incursion into Ireland earlier than conventional surveillance methods. Using 7,743,138 milk recordings from 730,724 cows in 7037 herds between 2007 and 2012, linear mixed-effects models were developed to predict milk yield and alarms generated with temporally clustered deviations from predicted values. Additionally, hotspot spatial analyses were conducted at corresponding time points. Using a range of thresholds, our model generated alarms throughout September 2012, between 4 and 6 weeks prior to the first laboratory confirmation of SBV in Ireland. This system for monitoring milk yield represents both a potentially useful tool for early detection of disease, and a valuable foundation for developing similar tools using other metrics. Department of Agriculture, Food and the Marine

We investigated whether Ntwetwe virus—a novel orthobunyavirus discovered in a Ugandan girl with a fatal encephalopathy—was a common reason for hospital admission for children to Kiboga hospital, Uganda. A case–control was conducted between September 2019 and September 2020, including cases with severe neurological disease and mild febrile illness, matched to a healthy control without fever. Among 143 subjects, no cases with an acute infection were identified. This result suggests that Ntwetwe virus does not cause a major burden of disease amongst children presenting to Kiboga hospital during the study period.

Arthropod-borne viruses have a significant impact on public health worldwide, and their (re) emergence put aside the importance of other circulating arboviruses. Therefore, this scoping review aims to identify and characterize the literature produced in recent years, focusing on aspects of three arboviruses: Mayaro virus, West Nile virus, and Oropouche orthobunyavirus. The Mayaro and Oropouche viruses were isolated for the first time in Trinidad and Tobago in 1954 and 1955, respectively, and have more recently caused numerous outbreaks. In addition, they have been incriminated as candidate diseases for human epidemics. On the other hand, the West Nile virus, isolated in Uganda in 1937, was initially considered of lower human importance. However, this virus is currently regarded as one of the most important zoonotic diseases in some parts of the world. Moreover, together, these viruses have been drawing the attention of public health authorities worldwide following recent outbreaks. To determine the global epidemiological profile of these three viruses, we used the Dimensions Database, which contains more than 100 million publications. In general, we identified 327 studies published from 1957 to 2020 for Mayaro virus, 7,213 studies published from 1943 to 2020 for West Nile virus and 152 studies published from 1961 to 2020 for Oropouche orthobunyavirus. Interestingly, we observed that Mayaro and Oropouche viruses had a significant increase in the number of publications in recent years. Thus, this comprehensive review will be helpful to guide future research based on the identified knowledge gaps.

Background A number of zoonotic mosquito-borne viruses have emerged in Europe in recent decades. Batai virus (BATV), a member of the genus Orthobunyavirus, is one example of a relatively newly emerged mosquito-borne virus, having been detected in mosquitoes and livestock. We conducted vector competency studies on three mosquito species at a low temperature to assess whether Aedes and Culex mosquito species are susceptible to infection with BATV. Methods Colonised lines of Aedes aegypti and Culex pipiens and a wild-caught species, Aedes detritus, were orally inoculated with BATV strain 53.2, originally isolated from mosquitoes trapped in Germany in 2009. Groups of blood-fed female mosquitoes were maintained at 20 °C for 7 or 14 days. Individual mosquitoes were screened for the presence of BATV in body, leg and saliva samples for evidence of infection, dissemination and transmission, respectively. BATV RNA was detected by reverse transcription-PCR, and positive results confirmed by virus isolation in Vero cells. Results Aedes detritus was highly susceptible to BATV, with an infection prevalence of ≥ 80% at both measurement time points. Disseminated infections were recorded in 30.7–41.6% of Ae. detritus, and evidence of virus transmission with BATV in saliva samples (n = 1, days post-infection: 14) was observed. Relatively lower rates of infection for Ae. aegypti and Cx. pipiens were observed, with no evidence of virus dissemination or transmission at either time point. Conclusions This study shows that Ae. detritus may be a competent vector for BATV at 20 °C, whereas Ae. aegypti and Cx. pipiens were not competent. Critically, the extrinsic incubation period appears to be ≤ 7 days for Ae. detritus, which may increase the onward transmissibility potential of BATV in these populations. Graphical Abstract

Background Tahyna orthobunyavirus (TAHV) is a mosquito-borne virus that may cause mild flu-like symptoms or neurological symptoms in humans. It is historically associated with floodplain habitats in Central Europe, and the mammalophilic floodwater mosquito, Aedes vexans, is thought to be the principal vector. There are few contemporary reports of TAHV transmission ecology within mosquitoes or their vertebrate hosts, and virus infections are rarely reported (and probably seldom diagnosed). The objectives of this study were to survey the mosquito population for TAHV in three floodwater habitats and describe host usage by the predominant floodwater mosquito species to potentially define TAHV transmission at these foci. Methods We performed longitudinal mosquito sampling along three major rivers in eastern Austria to characterize the mosquito community in floodplain habitats, and tested for the presence of TAHV in pools of mosquitoes. We characterized TAHV rescued from mosquito pool homogenate by sequencing. We surveyed mosquito host selection by analyzing mosquito blood meals. Results We identified TAHV in two pools of Ae. vexans captured along the Leitha River. This mosquito, and other floodwater mosquitoes, used large mammals (red deer, roe deer, wild boar) as their hosts. The sequence of the rescued virus was remarkably similar to other TAHV isolates from the region, dating back to the first isolate of TAHV in 1958. Conclusions In general, we confirmed that TAHV is most likely being transmitted by Ae. vexans, although the precise contribution of vertebrate-amplifying hosts to the ecological maintenance of the virus is unclear. The pattern of host selection matches the estimated exposure of the same large mammal species in the region to TAHV based on a recent serosurvey, but hares were also hosts at the site where TAHV was detected. We also confirm humans as hosts of two floodwater mosquito species, providing a potential mechanism for spillover of TAHV or other mosquito-borne viruses. Graphical Abstract

The Bunyavirales order of RNA viruses comprises emerging pathogens for which approved preventative or therapeutic measures for human use are not available. The genome of all Bunyavirales consists of negative-sense RNA segments wrapped by the virus-encoded nucleocapsid protein (NP) to form ribonucleoproteins (RNPs). RNPs represent the active template for RNA synthesis and the form in which the genome is packaged into virions, functions that require inherent flexibility. We present a pseudo-atomic model of a native RNP purified from Bunyamwera virus (BUNV), the prototypical Bunyavirales member, based on a cryo-electron microscopy (cryo-EM) average at 13 Å resolution with subsequent fitting of the BUNV NP crystal structure by molecular dynamics. We show the BUNV RNP possesses relaxed helical architecture, with successive helical turns separated by ∼18 Å. The model shows that adjacent NP monomers in the RNP chain interact laterally through flexible N- and C-terminal arms, with no helix-stabilizing interactions along the longitudinal axis. Instead, EM analysis of RNase-treated RNPs suggests their chain integrity is dependent on the encapsidated genomic RNA, thus providing the molecular basis for RNP flexibility. Overall, this work will assist in designing anti-viral compounds targeting the RNP and inform studies on bunyaviral RNP assembly, packaging and RNA replication.SignificanceBunyaviruses are emerging RNA viruses that cause significant disease and economic burden and for which vaccines or therapies approved for human use do not exist. The bunyavirus genome does not exist as naked RNA; instead it is wrapped up by the nucleoprotein (NP) to form a ribonucleoprotein (RNP). Using the prototypical bunyavirus, Bunyamwera virus, we determined the 3D structure of the native RNP, revealing a helical architecture with NP molecules linked by lateral contacts only, with no helix-stabilizing longitudinal contacts. Instead, the RNA genome itself plays a role in maintaining the helical architecture, allowing a high degree of flexibility that is critical for several stages of the virus replication cycle, such as segment circularization and genome packaging into virions.

We conducted serologic surveillance for flaviviruses and orthobunyaviruses in vertebrate animals in Mexico in 2018-2019. Sera were collected from 856 vertebrate animals, including 323 dogs, 223 horses, and 121 cows, from 16 species. The animals were from 3 states: Chihuahua in northwest Mexico (704 animals) and Guerrero and Michoacán on the Pacific Coast (27 and 125 animals, respectively). Sera were assayed by plaque reduction neutralization test using four flaviviruses (dengue type 2, St. Louis encephalitis, West Nile, and Zika viruses) and six orthobunyaviruses from the Bunyamwera (BUN) serogroup (Cache Valley, Lokern, Main Drain, Northway, Potosi, and Tensaw viruses). Antibodies to West Nile virus (WNV) were detected in 154 animals of 9 species, including 89 (39.9%) horses, 3 (21.4%) Indian peafowl, and 41 (12.7%) dogs. Antibodies to St. Louis encephalitis virus (SLEV) were detected in seven animals, including three (0.9%) dogs. Antibodies to Lokern virus (LOKV) were detected in 22 animals: 19 (8.5%) horses, 2 (1.7%) cows, and a dog (0.3%). Antibodies to Main Drain virus (MDV) were detected in three (1.3%) horses. WNV and LOKV activity was detected in all three states, SLEV activity was detected in Chihuahua and Michoacán, and MDV activity was detected in Chihuahua. None of the animals was seropositive for Cache Valley virus, the most common and widely distributed BUN serogroup virus in North America. In conclusion, we provide serologic evidence that select flaviviruses and BUN serogroup viruses infect vertebrate animals in Chihuahua, Guerrero, and Michoacán. We also provide the first evidence of LOKV and MDV activity in Mexico.

An adult male from Missouri sought care for fever, fatigue, and gastrointestinal symptoms. He had leukopenia and thrombocytopenia and was treated for a presumed tickborne illness. His condition deteriorated with respiratory and renal failure, lactic acidosis, and hypotension. Next-generation sequencing and phylogenetic analysis identified a reassortant Cache Valley virus.

We describe an Oropouche orthobunyavirus infection in a women 28 years of age in Colombia. We confirmed the diagnosis by viral isolation, quantitative reverse transcription PCR, and phylogenetic analysis of the small, medium, and large genomic segments. The virus is related to a strain isolated in Ecuador in 2016.

Mayaro virus (MAYV, Togaviridae) and Oropouche orthobunyavirus (OROV, Peribunyaviridae) are emerging enzootic arboviruses in Latin America. Outbreaks of febrile illness associated with MAYV and OROV have been reported among humans mainly in the northern region of Brazil since the 1980s, and recent data suggest these viruses have circulated also in more populated areas of western Brazil. MAYV shares mosquito vectors with yellow fever virus and it has been historically detected during yellow fever epidemics. Aiming to investigate the transmission of OROV and MAYV at the human-animal interface during a yellow fever, chikungunya and Zika outbreaks in Brazil, we conducted a retrospective molecular investigation in 810 wild and domestic animals, 106 febrile patients, and 22.931 vectors collected from 2016 to 2018 in Cuiaba and Campo Grande metropolitan regions, western Brazil. All samples tested negative for OROV and MAYV RNA by RT-qPCR. Findings presented here suggest no active circulation of MAYV and OROV in the sampled hosts. Active surveillance and retrospective investigations are instrumental approaches for the detection of cryptic and subclinical activity of enzootic arboviruses and together serve as a warning system to implement appropriate actions to prevent outbreaks.

Kaeng Khoi virus (KKV; Order: Bunyavirales), is an endemic viral infection of the wrinkle-lipped free-tailed bat (Chaerephon plicatus aka Tadarida plicata plicata). Little is known about the ecology and maintenance of KKV within the bat population, nor the infection dynamics and transmission among bats or between bats and other vertebrates. Therefore, KKV was studied in Kaeng Khoi cave, Saraburi province, Thailand, during 1973–1974 with the objectives to (1) characterize the seasonal infection rates of KKV in the context of the bat population ecology, and (2) describe the infection dynamics and viral shedding by naturally- and experimentally-infected bats. To this end, the free-tailed bat population was estimated by a series of timed photographs taken during the evening exodus. The case population of 900,000 adult bats doubled at the time of weaning of the young and returned to its previous level soon thereafter. The newborn bats had neutralizing antibodies to KKV that were likely to be maternal in origin. The KKV antibody prevalence in adult bats was high (69–91%) in March–May and low (29–40%) in August and September. Kaeng Khoi virus was isolated from 75% of dead and 50% of moribund bats, but was not found in nearly 400 apparently healthy bats. Virus was present in saliva, urine and blood of most of the naturally-moribund bats tested. Consistent with observations from naturally-infected bats, experimental infection of bats with KKV revealed significant liver pathology, also suggestive that this is not a benign infection. Kaeng Khoi virus is an endemic, year-round infection maintained by the annual recruitment of a large number of immunologically-naïve juvenile bats. Moreover, it produces an acute infection in the bat, either leading to death by hepatitis, or immunity.

Schmallenberg orthobunyavirus (SBV) was initially detected in 2011 in Germany from dairy cattle with fever and decreased milk yield. The virus infection is now established in many parts of the world with recurrent epidemics. SBV is transmitted through midges and transplacental. No direct virus transmission including via breeding has ever been demonstrated. In some bulls, however, the virus is detectable transiently, in low to minute quantities, in semen post-infection. While the infection is considered of low impact for the dairy industry, some SBV-free countries have adopted a zero-risk approach requiring bull semen batches to be tested for SBV RNA residues prior to import. This, in turn, obligates a protocol to enable sensitive detection of SBV RNA in semen samples for export purposes. Here, we describe how we established a now ISO/IEC 17025 accredited protocol that can effectively detect minute quantities of SBV RNA in semen and also its application to monitor bull semen during two outbreaks in the United Kingdom in 2012 and 2016. The data demonstrate that only a small number of bulls temporarily shed low amounts of SBV.

The newly emerging and re-emerging of viral contagion in the present scenario are of more extensive health concern. After a long calm of many years, an unexpected eruption of the Cat Que Virus in China is a source of our concern. Cat Que Virus is an Arbovirus and belongs to the Simbu serogroup of the Orthobunyavirus genus of the Bunyaviridae family. The Simbu serogroup is an extremely diverse group of Arbovirus. The arboviruses are causing the infection in multiple hosts including humans and various livestock. They can cause mild to life-threatening infections. Arboviruses expand their spectrum and are more observable in recent times. Human actions have the most significant geophysical impact on the environment. Changes in rainfall patterns, floods, and the risk of extreme weather events are all consequences of climate change. These events may be connected to the extension of permissive vectors, geographic ranges, and therefore provide more chance of growth and spread of potential vector. Arboviruses are responsible for the health hazard to millions of people globally. It is critical to concentrate research and surveillance on these emerging and re-emerging viruses, particularly arthropod-borne viral infections. The appropriate research and surveillance on them will help us for the development of effective control and treatment strategies and also reduce health problems. The present review summarizes the current broad outline of discovery, evolution and dispersal of this unknown virus.