Archives of Virology

Borealpox virus (BRPV; formerly Alaskapox) is an orthopoxvirus that has caused seven reported human infections in Alaska since 2015, including a fatal case in 2023. The natural reservoir of BRPV is unknown, although previous investigations have raised the possibility of wild small mammals transmitting the virus to humans, either through direct contact or via domestic cats and dogs. To understand which species may be involved in the maintenance and/or spillover of BRPV in Alaska, we trapped and sampled wild small mammals (including voles, shrews, and squirrels) in 2021 and 2024 near reported human case locations in Fairbanks and the Kenai Peninsula, respectively. We found evidence of previous exposure to orthopoxviruses in five species (including the House Mouse, Mus musculus) and detected BRPV DNA as well as viable virus in Northern Red-backed Voles (Clethrionomys rutilus). Further, screening of tissues from historical museum specimens revealed BRPV DNA in C. rutilus specimens collected in Denali National Park and Preserve in 1998 and 1999, 17 years before the first reported human case of BRPV. Phylogenomic analysis of all human and animal BRPV isolates strongly supports the hypothesis of local human infections through multiple spillover events. These findings suggest C. rutilus as a possible reservoir species for BRPV and indicate that BRPV has been present in Alaskan wild small-mammal populations for at least 25 years. Our study highlights the potential of museum collections to elucidate the temporal, spatial, and host ranges of emerging pathogens. Further museum- and field-based sampling will clarify the true geographic range of BRPV, which is closely related to Old World orthopoxviruses and may be circulating beyond North America.

Avian influenza virus (AIV) epidemiology is well-documented in temperate regions but remains poorly understood in isolated ecosystems like tropical oceanic islands. On these islands, seabirds nest in dense interspecific colonies where the role of different species as reservoirs and dispersers of AIV may vary greatly. Here, we examine the role of noddies (Anous spp.) as potential reservoirs for low pathogenic AIV and evaluate their potential as sentinel species for highly pathogenic AIV introduction on tropical oceanic islands. We analyzed blood samples from 11 seabird species across eight islands in the southwestern Indian Ocean (2015-2020). Noddies exhibited high, stable seroprevalence (30-45%), comparable to reservoir host species in temperate regions. The detection of two N7-positive noddies, sampled the same year on two distinct islands, provided direct molecular evidence that AIV actively circulates on these island colonies. While most other species showed low exposure, Bridled Terns (Onychoprion anaethetus) had exceptionally high seroprevalence (80%), though their reservoir status requires further investigation due to limited sampling. Given noddies consistent exposure and regional distribution, we recommend prioritizing islands with large noddy populations for AIV surveillance. Continued investigation of viral dynamics within and among islands is now called for to elucidate the ecological drivers of AIV maintenance and transmission.

Mpox virus (MPXV) gained increased attention following the declaration of two Public Health Emergencies of International Concern (PHEICs) in 2022 and 2024. The rapid spread of MPXV and the increase in human-to-human transmission highlighted the need for improved diagnostic tools for characterizing infection patterns and transmission dynamics. While PCR is effective for detecting active infections, serological approaches can help identify previous or asymptomatic infections and support retrospective surveillance. However, many serological assays developed during recent outbreaks have not been evaluated in endemic settings such as the Democratic Republic of the Congo (DRC). This study aims to define antigen-specific serological cutoff values to differentiate MPXV-seroreactive individuals from those with other orthopoxvirus (OPXV) exposure or different vaccination histories, specifically for use in the DRC. Here, we analyzed 134 individuals, divided into six distinct cohorts with different exposures. Serum samples were tested using Mesoscale Discovery (MSD) to screen for five MPXV and vaccinia virus (VACV) orthologous antigens: A29L/A27L, A35R/A33R, B6R/B5R, E8L/D8L, and M1R/L1R. Receiver operating characteristic (ROC) analysis identified the best-performing antigens and established seroreactivity cutoff values. A binary composite rule was also evaluated to improve the classification of these results. We identified three MPXV antigens, E8L (cut-off=12.33 AU/mL), A35R (cut-off=5.22 AU/mL), and B6R (cut-off=9.77 AU/mL), that showed the strongest discriminatory performance in the dataset. Collectively, these three antigens form a significant panel that demonstrated clear separation between our mpox survivor cohort and other OPXV-exposed individuals.

Thogotoviruses are a group of tick-borne, six-segmented, negative-sense single-stranded RNA viruses. These viruses encode an RNA-dependent RNA polymerase that recognizes promoter sequences located at the genomic termini to initiate RNA synthesis. The 5' and 3' ends of the genome bind to the polymerase and function as a promoter. Outside the catalytic center, they base-pair with each other to form a double-stranded RNA structure. This structure is referred to as the distal duplex and plays an important role in RNA synthesis. In this study, we investigated how the RNA sequence of the distal duplex influences polymerase activity using minigenome systems of two thogotoviruses, Oz virus (OZV) and Dhori virus (DHOV). Each virus exhibits distinct activities among its six segments. In OZV, one determinant of these differences is the base pair at positions 5'12 and 3'11 within the distal duplex, where promoter activity varies depending on whether the base pair is G:C or A:U. In contrast, the DHOV polymerase is not affected by this difference. These results indicate that, even within the genus Thogotovirus, viruses differ in whether they possess a mechanism that modulates promoter activity based on subtle sequence differences within the distal duplex. Furthermore, phylogenetic analysis and comparison of promoter sequences suggest that thogotoviruses can be divided into groups that do or do not regulate intersegment promoter activity via the base pair at positions 5'12 and 3'11. HighlightsO_LIMinigenome systems of Oz virus and Dhori virus reveal segment-specific differences in promoter activity C_LIO_LIThe distal duplex sequence modulates RNA synthesis in a virus-dependent manner C_LIO_LIThe base pair at positions 5'12/3'11 determines promoter activity in Oz virus but not in Dhori virus C_LIO_LIThogotoviruses can be divided into groups that do or do not regulate promoter activity via distal duplex sequence variation at positions 5'12/3'11 C_LI

The yerba mate psyllid (Gyropsylla spegazziniana) poses a significant threat to yerba mate crops, causing extensive economic losses. While some ecological aspects as well as control strategies have been studied, its associated viral diversity remains unexplored. Here, by generating the first RNA high-throughput analysis (HTS) of this pest, we explored the G. spegazziniana virome, revealing novel and diverse RNA viruses. We characterized five new viral members belonging to distinct families, with evolutionary cues of beny-like viruses (Benyviridae), picorna-like viruses (Picornaviridae), and sobemo-like viruses (Solemoviridae); which were tentatively named Gyropsylla spegazziniana beny-like virus 1 (GSBlV1), Gyropsylla spegazziniana picorna-like virus 1 (GSPlV1), and Gyropsylla spegazziniana sobemo-like virus 1-3 (GSSlV1-3), respectively. Phylogenetic analysis of the bi-segmented and highly divergent sobemo-like viruses showed a distinctive evolutionary trajectory of its encoding proteins at the periphery of recently reported invertebrate Sobelivirales. The beny-like virus belonged to a cluster of insect-associated beny-like viruse; while the picorna-like virus clustered together with psyllid-associated picorna-like viruses. These results highlight the existence of a complex virome within G. spegazziniana and establish the basis for future studies investigating the ecological roles, evolutionary dynamics, and potential biocontrol applications of these viruses in the G. spegazziniana -yerba mate eco-systems.

Hantavirids, specifically the members within the genus Orthohantavirus, represent a significant global public health threat, with bat-associated lineages challenging traditional reservoir paradigms. To investigate the genetic diversity of hantavirids in Southeast Asia, we conducted an expanded surveillance program in Lao PDR from May 2023 to October 2025 in bat populations and wild animals from local wet markets. Using molecular screening and deep sequencing to characterize hantavirids from bat populations and wild animals from local wet markets, we identified 20 positive samples across four bat species, recovering coding-complete genomes for multiple novel variants. Phylogenetic analysis confirmed that these viruses form a monophyletic group within Mobatvirus, resolving into two major subclades. The first subclade clustered with Quezon and Robina viruses found in fruit-eating bats. The second subclade further split into two lineages corresponding to Thakrong and Xuan Son viruses, which are associated with trident and leaf-nosed bats, respectively. Despite the strong host specificity observed, the detection of these viruses in a wet market, a critical interface for human-wildlife contact, indicates a potential zoonotic risk. These findings significantly expand the known diversity of mobatviruses in Laos and highlight the urgent need for serological surveillance in at-risk human populations to assess the potential for spillover.

Climate change and ecosystem collapse promote geographic expansion of vector-borne diseases, as witnessed by the recent incursions into Spain of the virus responsible for Crimean-Congo hemorrhagic fever (CCHFV). CCHFV is maintained in a tick-vertebrate cycle, principally involving ticks of the genus Hyalomma. Faced with the spread of Hyalomma ticks, and therefore the threat of a natural introduction of CCHFV into Western Europe, appropriate surveillance tools and control measures need to be implemented. It is both within and by the tick that CCHFV is maintained and spread in the environment. Despite prolonged portage of the virus, the tick is not overtly affected by CHFV infection. One of the prerequisites in conceiving control strategies is to understand the molecular mechanisms that intimately link the virus to its arthropod host. Despite the central role of the tick in the biology of CCHFV, these mechanisms are ill-defined, owing in part to the constraints associated with handling CCHFV-infected ticks in biosafety level 4 containment. In this study, we established the network of interactions between the S segment of the RNA genome Hazara virus (HAZV), a BSL-2 model of CCHFV, and Hyalomma proteins using ChIRP-MS technique. We identified 166 tick proteins, 21 of which have been described as RNA-binding proteins. Gene ontology and pathway enrichment analyses revealed that the S segment RNA interacts predominantly with mitochondrial proteins that belong to various mitochondrial metabolic pathways.

RNA viruses are common in tephritid fruit flies including the Queensland fruit fly, Australias most significant horticultural pest. For many their transmission, tissue tropism and load across host development remain unexplored. Yet these factors are important for host biology, ecology and pest management. We investigated Bactrocera tryoni orbivirus (OV), Bactrocera tryoni xinmovirus (XV), Bactrocera tryoni toti-like virus (TLV) and Bactrocera tryoni iflavirus species 2 (IVsp.2) that commonly coinfect B. tryoni laboratory populations. OV and XV transmission was vertical within and on eggs, while TLV transmission was vertical within eggs. IVsp.2 was not detected in eggs but was present in adults; however, IVsp.2 was horizontally transmitted, with viral load increasing with cohabitation time with infected flies. Horizontal transmission was not observed for the other viruses. OV had a similar load across all tissues, while XV was consistently more abundant in ovaries. TLV had a high viral load in the brain whereas IVsp.2 was abundant in the thorax, foregut and midgut. Besides differences in eggs, the viruses were detected in all other developmental stages, but viral load patterns differed: viral load remained constant for TLV, fluctuated for OV and XV, and was low in pre-adult stages and high in adults for IVsp.2. Our findings demonstrate distinct transmission strategies and tissue tropism among the viruses, providing new insights into their epidemiology and role in host biology. Furthermore, contrary to prevailing views that viruses are generally horizontally transmitted, most known RNA viruses of B. tryoni are vertically transmitted affecting the evolution of host-virus interactions.

We conducted a systematic review (PROSPERO CRD42023393345) characterising the epidemiology, outbreaks and mathematical models of Nipah virus (NiV), an important public health threat in South and Southeast Asia. We extracted 243 parameters, 89 risk factors, 39 models and 23 distinct outbreaks from 119 papers. IgG seroprevalence estimates ranged from 0% to 12.5%. NiV causes severe disease, with pooled case-fatality ratio estimates ranging widely from 9.1% (95%CI: 0.2%-41.3%) in Singapore to 81.9% (95%CI: 71.9%-88.9%) in Bangladesh. NiV's natural history is poorly characterised; we estimated a median incubation period of 8.77 days (95%CI: 7.53-10.02) based on 8 studies. Transmission parameter estimates were scarce, and all but one central estimate of the basic reproduction number were below 1. NiV mathematical models (n=39) were rarely fitted to data (n=8). All extracted information is accessible via our R package, epireview, a dynamic resource for informing responses to future outbreaks of NiV and related pathogens.

The caliciviruses include important human and animal pathogens such as norovirus, sapovirus and feline calicivirus. Viral reverse genetics is performed to understand the fundamental biology of these viruses, as well as a potential route to generate live-attenuated vaccines. Calicivirus reverse genetics systems have typically relied on either on the production of in vitro-transcribed RNA or plasmid-based rescue either from a mammalian promoter, or through supplementing with helper enzymes through means of a helper virus. Here, we present a novel system integrating vaccinia capping enzymes D1R and D12L encoded on plasmids as part of a system for Murine Norovirus (MNV) reverse genetics. Addition of D1R, D12L and T7 RNA polymerase-expressing plasmids increases the viral titres of rescued MNV in both BSR-T7 cells and transgenic BSR-T7CD300LF cells, and viral polyprotein abundance. When the murine norovirus receptor is expressed in BSR-T7CD300LFcells, viral titres increased 100-1000-fold compared over standard BSR-T7 cells. This system offers a robust, high-throughput means of assessing viral mutants.

Autophagy is a catabolic process used for the degradation of organelles and proteins. Macroautophagy involves the formation of autophagosomes and subsequent fusion with lysosomes to mediate cargo degradation. It also functions as a cellular defence mechanism, known as xenophagy, during infection. Previous studies show that different viruses manipulate the autophagy pathway of the host cell to assure successful replication and/or virion assembly. Vaccinia virus (VACV), the prototypic poxvirus, replicates exclusively in the cytoplasm of host cells. It is known that VACV infection causes LC3 lipidation and prevents autophagosome formation, yet the double membrane vesicles formed during autophagy do not serve as the source of the mature VACV membrane. To date the viral protein(s) causing increased LC3 lipidation have not been identified. Here we developed an image-based screening approach based on LC3 granularity to identify candidate VACV genes affecting its lipidation. We identify several candidate viral membrane proteins as effectors of LC3 lipidation, suggesting that the interplay between VACV and autophagy is more directed than previously thought.

Background: Human papillomaviruses (HPVs) pose a severe threat to global public health by driving nonmelanoma skin cancer (NMSC) and cervical cancer, with NMSC being one of the most common cancers worldwide. Epidermodysplasia verruciformis (EV) is an inborn error of immunity characterized by an increased susceptibility to persistent infection of cutaneous HPV and a high risk of NMSC. The genetic basis remains unknown in many patients with EV. Methods: We collected four unrelated pedigrees with EV. Genetic analysis identified five variants in JAK1 encoding the Janus kinase 1. Ex vivo models and patient-derived tissue were employed to evaluate the functional effects of JAK1 variants and delineate the pathogenic mechanisms. Results: We identified different variants in JAK1 in four pedigrees with dominant EV. Genetic analysis revealed five novel variants in JAK1, three of which resulted in nonsense-mediated mRNA decay (NMD). Functional assays identified a decreased phosphorylation of the signal transducers and activators of transcription (STATs), impaired interferon responses, and defective T cell activation. Immune dysregulation in patients, characterized by a reduced CD4/CD8 T cell ratio, decreased CD8 naive T cell proportion, and accumulated memory T cells, implies impaired antiviral immunity against HPV. Conclusions: Our findings confirm that JAK1 loss-of-function (LOF) variants underlie susceptibility to cutaneous HPV infection. [Funded by the National Natural Science Foundation of China (81788101, 81230015, 82394420, and 82394423), the National Key Research and Development Program of China (2022YFC2703900), the CAMS Innovation Fund for Medical Sciences (2021-I2M-1-018), and the Regione Lombardia, Italy (Innovative Research Project 1137-2010)].

Sarbecoviruses, including SARS-CoV and SARS-CoV-2, are frequently linked to Rhinolophus bats as their putative natural reservoirs. Angiotensin-converting enzyme 2 (ACE2), a host carboxypeptidase widely expressed in mammalian tissues, plays a critical role in sarbecovirus infection by serving as the cellular receptor for the viral spike (S) protein. Given recent human outbreaks and pandemics caused by members of sarbecoviruses, and the wide distribution of Rhinolophus bats, it is essential to maintain surveillance of these viruses while improving our understanding of their interactions with bat hosts, particularly the ACE2 receptor. However, while Rhinolophus bats from Asia have been relatively well studied, African Rhinolophus bats remain underrepresented and require further investigation. In this study, five Rhinolophus bat lung samples were obtained from Zambia, and ACE2 genes from these individuals were cloned and sequenced. We further evaluated the susceptibility of ACE2 variants to a panel of sarbecoviruses, revealing key residues that influence viral infectivity. ACE2 polymorphism was observed among Rhinolophus simulator individuals, revealing multiple ACE2 genotypes within the sampled population. However, R. simulator ACE2s did not permit infection by the clade 3 Afro-Eurasian sarbecoviruses tested in this study. Notably, RhGB01 and BM48-31 virus utilized only Rhinolophus blasii ACE2. Mutational analyses further suggested that ACE2 residues 31 and 41 play important roles in modulating spike-ACE2 interactions. This study reports 4 unique ACE2 sequences of R. simulator and R. blasii, and provides new insights into the molecular interactions between African Rhinolophus species ACE2s and the S protein of sarbecoviruses circulating in Africa and Europe. ImportanceAs putative natural reservoirs of sarbecoviruses, including SARS-CoV and SARS-CoV-2, Rhinolophus bats play a critical role in the emergence of zoonotic coronaviruses, making it essential to understand their interactions with these viruses for future pandemic preparedness. While Asian Rhinolophus bats have been relatively well studied, African species remain underrepresented, highlighting the need for further investigation. In this study, we cloned and sequenced ACE2 genes of five Rhinolophus bats collected in Zambia, Africa. We identified ACE2 polymorphism among Rhinolophus simulator individuals, although this variation was not associated with susceptibility to the clade 3 Afro-Eurasian sarbecoviruses examined. In addition, we identified key ACE2 residues that govern SARS-CoV-2 spike-ACE2 interactions and contribute to distinct infectivity patterns across species. These findings expand our understanding of the molecular determinants of sarbecovirus host range and support improved surveillance and risk assessment of emerging coronaviruses.

African swine fever (ASF) is a highly pathogenic disease caused by the African swine fever virus (ASFV) infection, which can affect pigs of all ages and breeds, posing significant threat to the global pig farming industry. The ASFV p30 protein is an early-expressed viral structural protein; however, its function is not fully understood. In this study, the interaction of viral p30 with host TRIM21 was identified. The ectopic TRIM21 inhibited ASFV replication, while knockdown or knockout of TRIM21 promoted ASFV replication. Further, p30 was found to interact with RIG-I-like receptor (RLR) signaling adaptor MAVS, and during ASFV infection, p30-TRIM21-MAVS interacted with each other. Mechanistically, TRIM21 activated the K27 polyubiquitination of MAVS to induce IRF3 mediated type I interferon (IFN) production, whereas p30 counteracted TRIM21 activated MAVS K27 polyubiquitination to evade RLR signaling mediated antiviral IFN induction. In summary, our study revealed a novel function of ASFV p30, and provided new insights into the immune evasion of ASFV.

Dengue disease remains a significant global health threat, with current vaccines exhibiting variable efficacy and safety concerns. Virus-like particles (VLPs) offer a promising alternative by mimicking native virus structures without infectious genomes. We engineered a mammalian expression plasmid encoding Dengue-1 prM and E proteins, optimized for secretion using Japanese Encephalitis virus signal sequences, and transiently expressed it in HeLa cells. Purified VLPs exhibited spherical morphology ([~]39 nm diameter) consistent with native virions, as confirmed by transmission electron microscopy. Immunization of mice with these VLPs elicited robust Dengue-1 specific IgG antibody responses. Our study demonstrates production of immunogenic Dengue-1 VLPs in HeLa cells, highlighting their potential as a vaccine candidate and a tool for serodiagnosis. Further characterization of VLP epitopes and protective efficacy is warranted to advance vaccine development. ImportanceDengue remains a significant global health challenge, with serotype 1 being one of the dominant strains causing recurrent outbreaks in Nepal. Existing vaccines demonstrate limited efficacy and pose significant safety concerns, particularly in seronegative populations. To address these limitations, this study explores virus-like particles (VLPs) as a safer alternative vaccine platform. VLPs elicit robust immunogenicity by mimicking the structure of native virus while completely lacking genetic components. This study combines DENV1 structural proteins with optimized expression systems to enhance immunogenicity. This work is particularly significant as the first dengue vaccine research conducted in Nepal, directly addressing antigenic mismatches between existing commercial vaccines and locally circulating viral strains. Furthermore, the study provides scalable platform for developing region-specific dengue vaccines for other serotypes and flaviviruses.

Deer tick virus (DTV), or lineage II Powassan virus, is an emergent tick-borne encephalitis virus in North America. Survivors frequently sustain neurologic sequelae. Nationally reported cases have been increasing. DTV is thought to be maintained in nature by multiple modes including horizontal transmission (from viremic host to tick), cofeeding transmission (between ticks feeding nearby) and by transovarial transmission (female to progeny). Analysis of the relative importance of each mode has been hindered by low enzootic transmission. In 2021, Marthas Vineyard, Massachusetts experienced an epizootic that allowed us to probe the modes of transmission on the island. We detected virus in 7.8% of questing deer tick nymphs (161 of 2063) and in 0.3% of lone star nymphs (2 of 678). Infected ticks had a highly focal distribution; 56% of infected ticks derived from only 4 of 71 collection sites. Tick mitochondrial genome sequencing demonstrated that infected ticks were not more likely to be siblings than negative ticks and, therefore, were unlikely to have inherited the infection. Whole viral genome sequencing revealed the presence of 3 genotypes, 58% were type1, 0.6% type2, and 13.7% type3. Tick host bloodmeal identification analyses determined that nymphs infected with type1 were significantly associated with having fed on shrews (50 of 94 type1 ticks, odds ratio=2.3, p<0.001). This is consistent with shrews serving as a reservoir. Ticks infected with type3, however, had no host associations, consistent with infection acquired by cofeeding. It may be that local DTV genetic variation is shaped by transmission modes or host associations. ImportanceDeer tick virus (DTV; Powassan lineage II) is a tick-borne encephalitis virus that causes a rare zoonosis in North America. Cases have been increasingly reported within the last decade. Is the recent risk trend due to increased transmission? How this virus is perpetuated in nature is not well understood. We took advantage of a natural epizootic on Marthas Vineyard to probe how the ticks there had become infected. Using a combination of viral whole genome sequencing and bloodmeal remnant identification in ticks, we find that the mode of transmission varied by viral genotype. One genotype is associated with ticks that had fed on shrews, and another did not depend on a specific reservoir host. Host associations may drive genetic diversity of deer tick virus and thus local host population dynamics may influence zoonotic risk.

Zoos may serve as sentinel sites for zoonotic vector-borne diseases. West Nile virus (WNV) and Usutu virus (USUV) are closely related orthoflaviviruses transmitted between Culex mosquitoes and a bird reservoir. Both viruses can also infect mammals, including humans, where they may cause symptoms and, more rarely, hospitalization and death. However, serological cross-reactivity between WNV and USUV complicates their differential diagnosis. Here, we aimed to reconstruct the dynamics of emergence of WNV in a zoo located in a newly affected area in Europe, using ELISA and Virus Neutralization Test (VNT) serological analysis of 1707 animal sera collected between 2015 and 2024. Combining this data in a model accounting for cross-reactivity with USUV, we estimated yearly forces of infection (FOI) by both viruses, and thus found that WNV likely circulated in the area one year prior to the first cases reported to the passive surveillance system. Our results also showed that, in the zoo, mammals and reptiles had a lower risk of infection than birds (relative risk of 0.14 [0.05; 0.28]), and that the exposure of birds to water (aquatic lifestyle or proximity to stagnant water) affected the risk. Finally, we estimated diagnosis parameters, including the sensitivity of the VNT (80.4% [76.5%; 84.3%]), the expected VNT titer value, and the level of serological cross-reactivity between viruses during the VNT. To conclude, our modelling framework allowed to disentangle the co-circulation of two closely related viruses, a crucial point in ensuring the reliable sentinel surveillance of these vector-borne zoonotic pathogens.

Usutu virus (USUV) is a mosquito-borne flavivirus that has recently expanded northwards in Europe and become endemic in the UK [1-3]. USUV emergence often precedes the closely related West Nile virus (WNV), potentially reflecting differences in epidemiological parameters [4, 5]. One key parameter is the extrinsic incubation period (EIP), the time required for a mosquito to become infectious following an infected blood meal. Here we present the first ever estimate of the temperature-dependent EIP for USUV in the vector Culex pipiens molestus. We were able to quantify the shortening of the EIP with temperature by re-analysing published laboratory data with bespoke Bayesian model that accounted for key features of the experimental design. Under typical UK summer temperatures, the median EIP (EIP50) of USUV is shorter than that of WNV, and the potential transmission season of USUV is both longer and geographically more extensive. Under RCP8.5 climate projections, WNV transmission suitability is expected to match or exceed current USUV levels between 2055 and 2065, highlighting the future threat to the UK from emerging mosquito-borne pathogens. Our findings support USUV as a precursor for WNV in northern Europe and provide a robust characterisation of a key epidemiological parameter of USUV, enabling accurate modelling of its transmission dynamics.

Background Venezuelan haemorrhagic fever (VHF), caused by Guanarito virus (GTOV), is a zoonotic disease endemic to the western plains of Venezuela. Despite decades of recognition, its epidemiology and clinical profile remain poorly characterised. Methodology We analysed individual level data from standardised case report forms submitted to the Venezuelan National Epidemiological Surveillance System between 2017 and 2024 for suspected VHF cases in Barinas, Apure, and Portuguesa. Demographic, clinical, and laboratory variables were examined to characterise temporal and geographical patterns and to define the clinical profile of VHF compared with endemic arboviral infections. Principal Findings Among 480 suspected cases, 72 (15.0%) were laboratory confirmed GTOV infections. Confirmed cases occurred predominantly in men engaged in agricultural or service related occupations, with the highest prevalence among individuals aged 46 to 90 years. A marked seasonal pattern was observed, with most cases occurring between September and January. The most frequently reported symptoms included headache, haemorrhage, sore throat, and diarrhoea. Compared with other endemic arboviral infections, GTOV was more strongly associated with headache, myalgia, sore throat, haemorrhage, and abdominal pain, delineating a distinct clinical phenotype relative to diseases caused by encephalitic alphaviruses, chikungunya virus, dengue virus, and Zika virus. The case fatality ratio among laboratory confirmed cases was 36.1% (95% CI: 25.1 to 48.3). GTOV infection was independently associated with mortality (adjusted relative risk [aRR] 3.66; 95% CI 2.28 to 5.87; p < 0.001), underscoring its substantial clinical severity. Conclusion GTOV remains endemically transmitted in western Venezuela, disproportionately affecting older men engaged in agricultural and service related occupations. Its seasonality and clinical phenotype, characterised by haemorrhage, sore throat, and gastrointestinal symptoms, highlight the need for clinical awareness and improved differential diagnosis, particularly in remote endemic settings with limited access to laboratory testing.

BackgroundFamily-based HIV index case testing identifies family members with unknown HIV status and links them to care. Data are limited in southern Ethiopia. MethodsA facility-based cross-sectional study was conducted among 377 adults on antiretroviral therapy (ART) in Wolaita Zone, Southern Ethiopia, from November 2022 to May 2023. Participants were selected using systematic random sampling. Data were collected via interviewer-administered semi-structured questionnaire. Multivariable logistic regression identified factors associated with index case family testing. Adjusted odds ratios (AOR) with 95% confidence intervals (CI) were calculated, and statistical significance was declared at p < 0.05. ResultsThe proportion of index case family testing for HIV was 84.9% (95% CI: 81.2- 88.6). In multivariable analysis, urban residence (AOR = 2.8; 95% CI: 1.16-6.75), duration on ART greater than 12 months (AOR = 13.0; 95% CI: 4.6-36.9), disclosure of HIV status to family members (AOR = 5.6; 95% CI: 1.9-16.5), discussion of HIV status with family members (AOR = 6.6; 95% CI: 1.9-23.2), and being counselled by health professionals to bring families for testing (AOR = 6.3; 95% CI: 2.1-19.0) were significantly associated with index case family testing. ConclusionThe prevalence of family-based HIV index case testing in Wolaita Zone was 84.9%, below the national 95% target. Health professionals should strengthen counselling on ART adherence, status disclosure, family discussion, and active referral to improve testing uptake among family members of people living with HIV.