The authors, a team of researchers led by Mohamed Abdulkadir Hussein, argue that this clinical anchoring is no longer adequate in a region where transmission patterns have shifted. Chikungunya increasingly spreads through urban and peri-urban human–mosquito cycles involving Aedes aegypti and, in some settings, Aedes albopictus, rather than arising solely from sylvatic spillover between forest mosquitoes and wild primates. Urban transmission cycles can amplify rapidly in dense city environments, which means the window for intervention between viral introduction and large-scale spread is narrow. Detection systems that only register the outbreak once patients fill clinics arrive too late to exploit that window.

The documented outbreak record illustrates both the scale of the threat and the unevenness of the data. The largest documented outbreak in the peer-reviewed evidence base occurred in Dire Dawa, Ethiopia, in 2019, with 41,162 suspected cases and 16 laboratory-confirmed cases in one outbreak report; a regional review using WHO-AFRO-linked surveillance synthesis describes the same event as involving more than 50,000 suspected cases. Kenya experienced major epidemics in 2004 and again in 2016 to 2018, with the 2004 outbreak on Lamu Island reaching an attack rate of 75 percent, one of the highest ever recorded for chikungunya. Djibouti confirmed a 2019 to 2020 urban outbreak, though the full citywide extent was not captured because of missing dedicated reporting; only a French Defense Community surveillance cohort reported 58 confirmed cases.

The gaps in that record are as revealing as the numbers themselves. For Tanzania, Uganda, Somalia, Rwanda, Burundi and South Sudan, extractable outbreak counts are largely absent, even though serologic evidence and reports of viral circulation exist for several of them. Reviews of African chikungunya transmission explicitly note disparities between reported cases, genomic data and dedicated reporting systems, and studies from Tanzania and Ethiopia emphasize inadequate laboratory capacity, under-recognition of cases and geographic heterogeneity in detection. In practical terms, a virus can be moving through mosquito populations and producing infections across entire provinces before any quantifiable signal reaches national or international reporting systems.

The case for reform is sharpened by climate change. Climatic suitability for the mosquitoes that transmit chikungunya is increasing, with warmer conditions expanding the geographic range of Aedes vectors and lengthening transmission seasons. Experimental and field evidence shows that temperature, rainfall and humidity shape both mosquito abundance and transmission potential in measurable ways. Higher temperatures generally increase mosquito infection rates and transmission efficiency, because viral replication within the mosquito accelerates as ambient temperature rises. Rainfall increases Aedes abundance by expanding breeding sites, and precipitation and temperature extremes are strong predictors of habitat suitability and hotspot formation across the region.

Recent outbreak analyses add a second layer to this climatic picture: heavy rainfall events combined with high temperatures can rapidly generate high vector densities and accelerate local spread within weeks. Broader climate-event cascades, in which droughts, floods and shifting rainfall patterns interact with urbanization, land use change and human mobility, intensify outbreak risk in ways that single-sector surveillance cannot capture. A public health ministry tracking only human cases sees the downstream consequence of these drivers; a system that also monitors the drivers themselves can anticipate them. This is the central technical argument for moving beyond pathogen-focused reporting toward surveillance of emergence.

The proposed alternative is a One Health early warning architecture that explicitly integrates human, animal and environmental intelligence. One Health surveillance, as defined in the literature the authors cite, includes monitoring of the drivers of emergence rather than pathogens alone, combining clinical and laboratory diagnosis with vector, environmental, epidemiological and genomic surveillance. Operational examples from climate-sensitive vector-borne disease programs show that such integration can reveal overlooked transmission clusters, track viral diversity and guide preventive action before notifications peak. Regional networks have demonstrated that long-term multisectoral collaboration strengthens diagnostic capacity, vector monitoring, risk assessment and coordinated response across borders, a capability directly relevant to East Africa’s transboundary arboviral risk.

Entomological surveillance is a critical component of this architecture, but the authors are careful to note its limitations. Field studies show that vector infection prevalence can be low and highly focal even when arboviruses are actively circulating, meaning that failure to detect virus in sampled mosquitoes does not imply absence of local risk. Nevertheless, vector surveillance still provides actionable early signals through metrics such as adult female density, egg counts, larval habitat mapping, vector distribution and risk stratification. In Mombasa, for example, entomological investigations detected chikungunya virus in Aedes vittatus while Aedes aegypti remained the dominant collected vector, showing how vector community composition itself carries information about transmission potential. Combined with epidemiological and environmental data, these indicators support targeted vector control and rational prioritization of scarce resources.

Geography reinforces the integrated approach. Documented outbreaks cluster in coastal, urban and transport-linked settings such as Lamu, Mombasa, Kilifi, Dire Dawa and Djibouti City, locations where port traffic, trade corridors and rapid urban growth concentrate both human mobility and Aedes breeding habitat. The main periods of increased transmission in the region were the 2004 to 2005 East African resurgence centered on Kenya, the 2007 to 2008 period of Tanzanian activity, and the 2016 to 2020 wave that affected Mandera, Mombasa, Somalia, Ethiopia and Djibouti. Because these transmission chains follow movement and trade, an early warning system confined to one country or one data stream will systematically miss the cross-border seeding events that ignite new outbreaks.

The policy conclusion the authors draw is unambiguous: ministries of health should move from passive case reporting toward regionally coordinated One Health surveillance platforms that link routine human case detection with mosquito monitoring and climate intelligence. Such platforms would require interoperable data systems, shared laboratory protocols and cross-border alert thresholds, allowing a signal detected in vector or climate data in one country to trigger preparatory action in neighboring ones. East Africa faces precisely the constraints this approach is designed to overcome: fragmented sectoral systems, weak data sharing, uneven laboratory capacity and rising exposure driven by mobility, urban growth and climate variability. Earlier detection of chikungunya, the analysis concludes, will depend less on counting human cases after spread has begun and more on integrating the entomological, environmental and climatic signals that precede them.

Subject of Research: One Health surveillance for chikungunya early warning in East Africa

Article Title: One Health surveillance integrating human, mosquito, and climate data for early warning of chikungunya outbreaks in East Africa

Article References: One Health surveillance integrating human, mosquito, and climate data for early warning of chikungunya outbreaks in East Africa. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: chikungunya, One Health, East Africa, Aedes aegypti, Aedes albopictus, climate change, surveillance, vector-borne disease, early warning, arbovirus, Ethiopia, Kenya

The drug in question is favipiravir, a broad-spectrum nucleoside analogue that inhibits viral RNA-dependent RNA polymerases and is already approved for influenza treatment in several countries. The research team began by characterizing its activity against Oropouche virus in cultured Vero E6 cells, comparing it directly with ribavirin, another broad-spectrum antiviral. Favipiravir proved substantially more potent, with a mean half-maximal effective concentration of 28.4 micromolar compared with 115.7 micromolar for ribavirin. Untreated infected cells developed marked cytopathic effects, and ribavirin offered only limited protection, whereas favipiravir preserved cellular morphology in a dose-dependent fashion and robustly reduced infectious virus production. Time-of-addition experiments pinpointed the drug’s stage of action: treatment significantly reduced viral titers when administered at the time of infection or during early replication, but not at the maturation stage, consistent with favipiravir’s established mechanism of interfering with viral RNA synthesis during the post-entry replication phase.

The decisive test came in vivo. The researchers used a lethal Syrian hamster model, infecting animals intraperitoneally with 5.4 × 10⁵ plaque-forming units of the OROV TRVL 9760 strain. All vehicle-treated animals succumbed to infection by three days post-infection, without preceding overt clinical symptoms or weight loss—a fulminant course that underscores how aggressive lethal Oropouche disease can be in this model. In stark contrast, animals receiving high-dose favipiravir at 600 milligrams per kilogram per day, given orally twice daily beginning one hour before infection and continuing for six days, survived the entire 26-day observation period without any clinical signs and steadily gained weight. Lower doses of favipiravir and both tested doses of ribavirin conferred only partial protection, and notably, some animals in the ribavirin groups developed neurological symptoms, including ataxia, hindlimb weakness, and paralysis, after treatment ceased.

Virological measurements explained these divergent outcomes. Using plaque assays and reverse transcription quantitative PCR, the team tracked viral loads in serum, brain, liver, and spleen at multiple time points. Vehicle-treated animals carried high viral burdens in all tissues at two days post-infection. High-dose favipiravir, by contrast, suppressed viral replication so completely that no viral RNA or infectious virus was detectable in any tissue at any time point examined. The suboptimal regimens told a more cautionary story: although low-dose favipiravir and ribavirin reduced infectious virus in serum, liver, and spleen, infectious virus persisted in the brains of these animals at six and eight days post-infection, indicating incomplete clearance from the central nervous system that correlated with the delayed neurological disease observed after treatment withdrawal. The message is clear—insufficient antiviral pressure allows viral neuroinvasion, and neuroinvasion drives fatal disease.

Perhaps the most clinically encouraging finding concerns timing. In outbreak settings, patients rarely present before infection is already established, so a drug that works only as prophylaxis would be of limited value. The researchers therefore tested delayed treatment, initiating favipiravir at one hour before infection, at the time of infection, or at 6, 24, or 48 hours after infection. Strikingly, animals that began treatment as late as 24 hours post-infection were fully protected, with 100 percent survival and complete suppression of viral replication in systemic organs and the central nervous system. Even at 48 hours post-infection, when the therapeutic window was narrowing, favipiravir still conferred partial protection, with 50 percent survival and consistent weight gain among survivors. This therapeutic window, demonstrated in a model where untreated infection is uniformly lethal within days, substantially strengthens the case for favipiravir as a practical candidate for human Oropouche disease.

Beyond efficacy, the study’s second major contribution is mechanistic. To define the host responses associated with Oropouche virus pathogenesis and their modulation by antiviral therapy, the team performed tissue-resolved transcriptomic profiling—RNA sequencing of liver and brain collected at two days post-infection. Because the Syrian hamster genome remains less comprehensively annotated than the mouse genome, hamster genes were functionally annotated through their mouse orthologs. Principal component analysis revealed a clear transcriptional separation between infected and uninfected animals in both tissues, while favipiravir-treated animals clustered near uninfected controls, indicating that the infection-driven transcriptional upheaval was largely suppressed by the drug. This is, to the authors’ knowledge, the first in vivo, tissue-resolved transcriptomic framework of Oropouche virus infection.

The transcriptomic signatures in infected animals were distinctive and, in places, ominous. In the liver, where the virus replicated robustly, infection induced upregulation of genes involved in chemotaxis, cytokine signaling, myeloid cell differentiation, and interferon responses, alongside downregulation of metabolic pathways governing energy production and fatty acid metabolism. In the brain, antiviral and inflammatory programs were induced even more strongly, accompanied by pathways promoting immune cell recruitment. Quantitative PCR validation of selected interferon-stimulated genes—Cxcl10, Rsad2, and Isg15—confirmed strong induction at two days post-infection in both tissues of untreated animals, which was suppressed by both favipiravir and ribavirin at that early stage. At later time points, however, Rsad2 and Isg15 expression tended to remain elevated in ribavirin-treated animals, correlating with their persistent brain viral loads, whereas expression stayed low in favipiravir-treated animals. Interestingly, the canonical inflammatory cytokines Il6, Il10, and Tnf-alpha showed no significant changes at two days post-infection and did not track with viral replication, suggesting they are unlikely to be major drivers of Oropouche disease in this model.

The metabolic findings deserve particular attention. Although liver involvement is not a prominent feature of typical Oropouche fever, recent fatal human infections have been associated with markedly elevated aminotransferase levels and liver injury biomarkers, and independent studies have demonstrated hepatic infection and inflammatory responses in human liver organoids and an experimental mouse model. The simultaneous enrichment of pathways associated with positive regulation of innate immune responses and negative regulation of defense responses in high-burden animals suggests a complex, potentially dysregulated host response, in which sustained antiviral and inflammatory signaling coexists with regulatory mechanisms that constrain excessive immune activation. When viral replication remains high, such regulation appears insufficient. The concurrent downregulation of energetic, lipid metabolic, and mitochondrial pathways in the liver implies that cellular stress during high-burden infection may contribute to tissue dysfunction and injury, meaning that Oropouche pathogenesis likely reflects not only direct viral replication but also the interplay between persistent viral burden, dysregulated immunity, and disrupted metabolic homeostasis.

The authors are candid about the study’s limitations. The reliance on mouse orthologs for gene annotation means hamster-specific transcriptional features and genes lacking confident mouse orthologs may have been underrepresented. Additionally, because all vehicle-treated animals reached the humane endpoint before six days post-infection, direct comparisons of gene expression between untreated and treated animals at later time points were impossible, leaving some uncertainty about whether the later profiles reflect favipiravir’s effects or the absence of ongoing infection. These caveats notwithstanding, the study extends earlier work by Rodrigues and colleagues, who established the Syrian hamster as a relevant model of Oropouche pathogenesis, by integrating tissue-resolved transcriptomics with therapeutic intervention in a single experimental framework.

Translational considerations will shape what happens next. Favipiravir offers genuine advantages over other polymerase-targeting candidates such as 4′-fluorouridine, including oral bioavailability and prior clinical use against multiple viral diseases, and its demonstrated efficacy with delayed initiation enhances its relevance for outbreak settings where early diagnosis is difficult. Yet the drug carries known safety liabilities: teratogenic and embryotoxic effects, and an association with elevated serum uric acid and hyperuricemia. These concerns are especially pertinent for Oropouche virus, given the growing recognition of congenital and pregnancy-associated disease. The authors emphasize that further studies addressing pharmacokinetics, optimal dosing, treatment duration, and safety in relevant populations will be required before clinical application. Even so, the findings provide strong preclinical evidence that timely, potent antiviral intervention can prevent central nervous system invasion, suppress pathogenic inflammatory and metabolic programs, and avert lethal Oropouche disease—transforming the outlook for a pathogen that, until now, medicine could only watch.

Subject of Research: Favipiravir efficacy and host transcriptomic responses in lethal Oropouche virus infection

Article Title: Integrated in vivo and transcriptomic analyses of lethal Oropouche virus infection reveal suppression of pathogenic host responses by antiviral therapy

Article References: Sousa Moraes, C., Gonzalez, G., Sato, A., Miki, S., Inoue, A., Tabata, K., Kranrod, J. W., Kabamba, C. F., Ohnuma, A., Matsuno, K., Harada, R., Saito, S., Akimoto, N., Sasaki, M., Orba, Y., Hall, W. W., Sawa, H., & Itakura, Y. (2026). Integrated in vivo and transcriptomic analyses of lethal Oropouche virus infection reveal suppression of pathogenic host responses by antiviral therapy. PLOS Pathogens, 22(10), e1014647. https://doi.org/10.1371/journal.ppat.1014647

Image Credits: AI Generated

DOI: 10.1371/journal.ppat.1014647

Keywords: Oropouche virus, favipiravir, antiviral therapy, arbovirus, neuroinvasion, Syrian hamster model, transcriptomics, interferon response, ribavirin, PLOS Pathogens, emerging infectious disease, RNA virus

The team, led by Jinping Dou and Shuang Wei, who contributed equally to the work, with corresponding authors Xingjian Liu and Yinü Li, worked from GETV-BJ0304, an attenuated strain previously isolated by the group. Attenuated strains are attractive backbones for reverse genetics systems because they can be manipulated under less stringent containment considerations while still recapitulating core features of alphavirus biology. Using a seamless cloning method, the researchers assembled the complete viral genome rapidly, avoiding the restriction-site scars and extraneous sequences that plague older ligation-based approaches. Seamless assembly matters in this context because alphavirus genomes are compact and densely packed; even small insertions of nonviral sequence at junction sites can alter replication kinetics and confound downstream experiments.

Getah virus belongs to the Alphavirus genus within the Togaviridae family, a group characterized by a positive-sense, single-stranded RNA genome of roughly 11 to 12 kilobases. The genome is organized into two open reading frames: the nonstructural polyprotein encoded at the 5′ end, which supplies the replication machinery, and the structural polyprotein at the 3′ end, which is translated from a subgenomic RNA. This subgenomic RNA is produced from an internal promoter, conventionally called the 26S subgenomic promoter (26SGP), which drives very high levels of structural protein expression during infection. That architecture creates two natural insertion points for a reporter gene, and each comes with distinct trade-offs that the Beijing team set out to quantify.

The first strategy exploits the 2A self-cleaving peptide, a short sequence, originally described in picornaviruses, that induces ribosomal skipping during translation. When a reporter gene such as enhanced green fluorescent protein (EGFP) is fused to a viral polyprotein through a 2A sequence, the translating ribosome ‘skips’ a peptide bond at the 2A motif, releasing the reporter as a largely separate protein while leaving the viral polyprotein essentially intact. The elegance of this approach is that the reporter is expressed from the same mRNA as the viral protein, so reporter output tracks faithfully with viral gene expression, and the viral genome length increases only modestly. The second strategy inserts an additional copy of the 26S subgenomic promoter upstream of the reporter gene, creating a second subgenomic RNA dedicated to reporter translation. This duplicated-promoter design can drive very high reporter expression, but it adds substantial sequence to the genome and introduces an extra promoter element that the viral replication machinery must recognize and that recombination can act upon.

Which strategy wins has often been assumed rather than tested, particularly for attenuated alphavirus backbones where genomic flexibility may differ from that of virulent laboratory strains. The researchers constructed reporter viruses carrying EGFP through both routes and then subjected the resulting recombinants to a battery of characterization assays. The results were decisive: for the GETV-BJ0304 backbone, the 2A self-cleaving peptide strategy proved highly efficient and stable. The recombinant virus, designated GETV-2A/EGFP, displayed high infection efficiency and, importantly, maintained its reporter over serial passages, a property that many reporter alphaviruses lose as deletion or mutation of the foreign sequence confers a replicative advantage.

Genetic stability is the quiet battleground of reporter virology. A reporter virus that sheds its fluorescent cargo after a few rounds of replication is worse than useless, because it silently biases experiments: the cells that remain fluorescent are those infected by the fittest, reporter-retaining variants, which may not represent the population the researcher intends to study. By demonstrating that GETV-2A/EGFP retains high-level EGFP expression through extended passaging, the study provides a technical platform whose fluorescence can be taken as a reliable proxy for infection. That reliability underpins quantitative applications ranging from neutralization assays and antiviral screening to single-cell analyses of viral spread, where fluorescence intensity and infected-cell counts feed directly into the analysis.

The comparison also carries broader lessons for alphavirus reverse genetics. The 26S promoter duplication strategy, while capable of strong expression, imposes a larger genomic burden and creates duplicated promoter sequences that are intrinsically recombination-prone. In an attenuated backbone, where replication fidelity and genomic tolerance may already be strained, that burden appears to be decisive. The 2A approach, by contrast, keeps the added sequence short and avoids duplicating regulatory elements, aligning reporter expression with the natural translational output of the viral polyprotein. The finding does not necessarily generalize to every alphavirus or every backbone, but it offers an evidence-based default for researchers constructing reporter clones in attenuated strains, replacing intuition with head-to-head data.

Why does Getah virus warrant this level of technical investment? The virus circulates in a transmission cycle involving mosquitoes and vertebrate hosts, and it has caused notable epizootics in horses, characterized by fever, edema, and urticarial rash, as well as reproductive disease and neurological signs in piglets. Although GETV is not currently a major human pathogen, its recent outbreaks and demonstrated potential for increased virulence have placed it alongside other arboviruses as a public-safety concern. Climate change, expanding mosquito vector ranges, and intensification of livestock production all create conditions favorable to emergence. A robust reverse genetics system is the prerequisite for dissecting which viral proteins and RNA elements drive host range, virulence, and transmission, and for rationally designing attenuated vaccine candidates or antiviral targets rather than discovering them by trial and error.

The platform described in the study enables exactly that dissection. With a stable fluorescent reporter embedded in an otherwise authentic viral genome, researchers can monitor replication in real time, quantify infection in the presence of interfering RNAs or candidate drugs, and screen host genes for factors that restrict or support GETV invasion. The authors frame the system as a crucial technical platform for in-depth analysis of GETV replication and pathogenic mechanisms, as well as for exploring new strategies that help the host resist viral invasion. In practical terms, that means the clone can serve as the starting point for mutant libraries, for structure-function studies of the nonstructural proteins, and for testing how specific mutations alter tropism in mosquito and mammalian cells.

The work, funded by China’s National Key Research and Development Program, the National Natural Sciences Foundation of China, the Agricultural Science and Technology Innovation Program, and the Central Public-interest Scientific Institution Basal Research Fund, arrives as an open-access publication, making the construction logic and characterization data available to laboratories worldwide. As arboviruses continue to test the boundaries of veterinary and public health preparedness, tools of this kind, a rapidly assembled infectious clone paired with a validated, stable reporter strategy, convert an emerging pathogen from an opaque threat into an experimentally tractable one. For Getah virus, the 2A-based design now stands as the benchmark against which future reporter constructs will be measured.

Subject of Research: Construction and comparison of reporter gene insertion strategies in Getah virus reverse genetics systems

Article Title: Comparison and characterization of construction strategies for Getah virus infectious clones with stable, high-level expression of reporter gene

Article References: Dou, J., Wei, S., Gao, X., Wu, T., Zhao, Z., Zhang, Z., Liu, X., & Li, Y. (2026). Comparison and characterization of construction strategies for Getah virus infectious clones with stable, high-level expression of reporter gene. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06457-x

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06457-x

Keywords: Getah virus, alphavirus, reverse genetics, infectious clone, reporter gene, EGFP, 2A self-cleaving peptide, subgenomic promoter, arbovirus, genetic stability, viral replication, veterinary virology

The study, published in Virology Journal, focused on Culex pipiens sensu lato and Culiseta annulata, two species that dominate the UK mosquito fauna and are considered among the most plausible vectors should arboviruses such as West Nile or Usutu virus establish local transmission cycles. Between 2021 and 2022, the team collected adult mosquitoes across the grounds of the two zoological collections, sites chosen deliberately because zoos concentrate large numbers of animals in outdoor enclosures where mosquitoes feed readily. That combination of abundant vectors, diverse vertebrate hosts and regular human visitors makes zoological collections potential interfaces for virus exchange between mosquitoes, animals and people, and therefore valuable sentinel locations for surveillance.

In total, 4,042 mosquitoes were processed and sequenced across 44 pools. The researchers extracted total nucleic acids and applied a metagenomic sequencing strategy designed to capture both RNA and DNA viruses, allowing them to recover viral genomes without relying on prior assumptions about which viruses might be present. Bioinformatic assembly and taxonomic classification of the resulting reads yielded 26 viral genomes, a striking haul for a country whose mosquito viromes have remained comparatively understudied. Nine of these represented entirely novel species, distributed across both RNA and DNA virus families, underscoring how much basic viral diversity in northern European mosquitoes still awaits description.

A consistent pattern emerged across the sampling sites: several viruses were detected in every pool analysed, indicating substantial overlap in virome composition between the two zoos. This shared core of viruses suggests that certain mosquito-associated viruses are widespread and stable components of the local mosquito fauna rather than isolated curiosities confined to a single habitat. Such ubiquity matters for risk assessment, because a virus that maintains itself efficiently across geographically separated mosquito populations has, by definition, the ecological flexibility that emergence requires, even if most of these viruses ultimately prove harmless to vertebrates.

The headline findings are two novel orthobunyaviruses, named Atherstone virus and Deva virus, belonging to the family Peribunyaviridae. Orthobunyaviruses are a genus with a serious pedigree: it includes recognised human and animal pathogens such as Schmallenberg virus, which devastated European ruminant farming after its emergence in 2011, and Oropouche virus, a growing public health concern in the Americas. The tripartite RNA genomes of orthobunyaviruses encode a viral RNA-dependent RNA polymerase on the large segment, surface glycoproteins on the medium segment, and nucleoprotein plus accessory proteins on the small segment. Finding two previously unknown members of this genus in British mosquitoes immediately elevates them to candidates for closer scrutiny.

Not all orthobunyaviruses pose equal risk, and the study went beyond simple detection to ask which of the two new viruses resembles a genuine arbovirus, capable of replicating in both mosquitoes and vertebrate hosts. The team employed MosViR, a machine-learning classification tool trained on known mosquito viruses to predict whether a given virus is likely to be mosquito-restricted or arthropod-borne. For Atherstone virus, detected at both zoos, the prediction pointed towards arbovirus status, a result that alone would justify follow-up. More compelling still was the genomic evidence: Atherstone virus carries an open reading frame encoding a non-structural protein S, or NSs, a well-characterised virulence factor in orthobunyaviruses that antagonises host antiviral responses, including the interferon system, and is a hallmark of pathogenic members of the genus.

Deva virus tells a different story. Its small segment lacks an NSs open reading frame altogether, and MosViR did not predict it to be an arbovirus. The absence of NSs, combined with the absence of a vertebrate-infecting signature, is consistent with Deva virus being an insect-specific virus, locked into replication within mosquito cells and their close relatives. Insect-specific viruses of this kind are increasingly recognised as common and sometimes abundant residents of mosquito viromes. Although they do not infect vertebrates directly, they are far from biologically irrelevant: they can modulate mosquito immunity, compete with arboviruses for cellular resources, and in some cases reduce the ability of mosquitoes to transmit pathogenic viruses, making them subjects of interest both for basic virology and for potential interference-based control strategies.

The broader viral inventory recovered in the study reinforces this picture of a layered virome. Alongside the orthobunyaviruses, the sequencing identified viruses spanning multiple families, including flavivirus-like and other RNA virus groups as well as DNA viruses, with several classified as novel species. Distinguishing arboviruses from insect-specific viruses is one of the central analytical challenges in mosquito metagenomics, because both can be present in the same sample and their genomes can be difficult to interpret from sequence data alone. Tools such as MosViR, combined with comparative genomics against reference databases and catalogues of known arboviruses, provide a probabilistic framework for triage, flagging which discoveries warrant experimental characterisation in cell culture and vertebrate systems and which can be provisionally set aside as likely insect-restricted.

Why does this matter for the United Kingdom specifically? The country sits at the northern edge of the range of many mosquito species, and climate warming, changes in land use and the movement of animals and goods are all expected to alter the dynamics of mosquito-borne disease in temperate Europe. Usutu virus has already established itself in British birds and mosquitoes, and West Nile virus circulates periodically in neighbouring countries. Risk frameworks built around these known threats are essential, but the new study argues that they should be complemented by surveillance for the unknown: viruses already resident in local vectors whose properties have never been tested. A virus that today appears to be insect-specific could, through reassortment with a related pathogen or through evolutionary change, acquire new capabilities. Orthobunyaviruses are particularly notable in this respect because their segmented genomes can reassort when mosquitoes are co-infected with related viruses, generating novel combinations with unpredictable host ranges.

The authors are careful not to overstate the immediate danger. Detection of a viral genome in a mosquito does not demonstrate that the virus infects or harms vertebrates, and neither Atherstone nor Deva virus has been shown to cause disease. What the study provides is a prioritised list of candidates and a demonstration of method: that large-scale metagenomic surveillance of UK mosquitoes is feasible, productive and capable of revealing both the diversity of local viromes and the specific viruses that merit laboratory follow-up. Isolation of Atherstone virus, characterisation of its host range, and serological surveys of animals and humans near the sampling sites would be the logical next steps. In the meantime, the work adds the United Kingdom to the growing map of regions where the viruses closest to home, rather than those arriving from abroad, are proving to be the first order of business for emerging infection surveillance.

Subject of Research: Metagenomic surveillance of mosquito viromes at two UK zoos reveals novel mosquito-associated orthobunyaviruses

Article Title: Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK

Article References: Pilgrim, J., Seechurn, N., Cunningham-Oakes, E., Gillespie, L., Dobbs, P., Lopez, J., Kohl, A., Hughes, G. L., Blagrove, M. S. C., Baylis, M., & Darby, A. C. (2026). Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK. Virology Journal. https://doi.org/10.1186/s12985-026-03305-z

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03305-z

Keywords: orthobunyavirus, mosquito, virome, metagenomics, arbovirus, Culex pipiens, Culiseta annulata, surveillance, zoonotic risk, insect-specific virus, United Kingdom, Peribunyaviridae