ETIDIOH - NEW

  Abstract The ongoing epizootic of highly pathogenic avian influenza (HPAI) continues to cause massive deaths in wildlife . Fundamental understanding of its disease ecology in natural populations is urgently needed. This knowledge has been hindered by the difficulty of acquiring data on epidemic dynamics . Here, using data collected from a threatened population of Dalmatian pelicans (Pelecanus crispus), we recover the epidemiological and evolutionary history of one of the largest HPAI wildlife mortality events . The results show that this devastating outbreak was likely seeded by a single introduction associated with movement of the species . By estimating epidemiological features of two consecutive outbreaks in the same population, we show that panzootic H5N1 since 2022 likely exhibits higher transmissibility and longer shedding time in non-reservoir birds , compared to previous H5NX subtypes. We also evaluate effectiveness of past and future control measures : carcass removal du...

  Abstract In this study, the phenotypic consequences of naturally occurring single nucleotide polymorphisms (SNPs) in the Middle East respiratory syndrome coronavirus (MERS-CoV) Spike protein were investigated. The impact of Spike mutations on the syncytia formation and neutralisation of contemporary MERS-CoV strains is not currently well understood. Mutations were identified by aligning 584 MERS-CoV Spike sequences from either human clinical isolates collected between 2012 and 2024 or from a clinical isolate that had been passaged in human cells . Fifteen SNPs of interest occurring in the N-terminal domain (NTD), receptor binding domain (RBD) and adjacent to the S1/S2 cleavage site were selected for further characterisation based on their location in the Spike protein, frequency and identification in previous studies. A contemporary clade B, lineage 5 wildtype Spike sequence , obtained from a human MERS-CoV clinical isolate , was used as the backbone in this study . The mutations...

  ABSTRACT H9N2 avian influenza viruses (AIVs) remain a significant economic burden on poultry production and a persistent zoonotic threat . Hemagglutinin (HA), a surface glycoprotein mediating viral entry and pathogenesis , critically depends on thermostability for its function. Our previous study indicated that recent H9N2 AIVs have experienced a reduction in hemagglutination activity and exhibit low HA thermostability ; however, the underlying molecular determinants for this instability remain poorly defined. To address this gap, we employed an in vitro-directed evolution approach to identify HA mutations that enhance thermostability. By subjecting a diverse HA mutant library to iterative heat selection at 48°C , we isolated several HA-stabilizing mutations , including L29I, N133S, N210D, G266R, D387N, A423T, and E509G, and confirmed their effect by site-directed mutagenesis. Further characterization revealed a complex interplay between HA stability, receptor binding specificity...

  Highlights •  MERS-CoV remains an endemic camel-associated betacoronavirus with ongoing zoonotic spillover. •  Viral evolution shows three major clades with lineage B predominance and documented recombination. •  DPP4-mediated entry, immune suppression , and T-cell apoptosis drive severe disease and high fatality. •  Diagnosis relies primarily on rRT-PCR , while treatments and vaccines remain experimental. •  Strengthened One-Health surveillance , IPC, and genomic monitoring are essential for pandemic preparedness. Abstract Middle East respiratory syndrome coronavirus (MERS-CoV) is a zoonotic beta coronavirus identified in 2012 that circulates in dromedary camels and occasionally infects humans. Although community spread is limited , the disease shows a high case fatality rate near 36 percent and has caused hospital outbreaks such as the 2015 South Korea event . The viral spike binds the DPP4 (CD26) receptor, enabling entry into airway epithelial and sele...

  Abstract While influenza A virus undergoes rapid antigenic drift in humans, at least some subtypes, such as H3, have relatively stable antigenicity in natural waterfowl reservoirs, despite the presence of immune pressure . However, the underlying mechanisms remain poorly understood. This study identified and characterized 187 antibodies to H3 hemagglutinin from experimentally infected mallard ducks , 18 of which were further analyzed by cryo-EM . Compared with human H3 antibodies , duck H3 antibodies exhibited higher glycan-binding propensity , more balanced immunodominance hierarchy , and targeted distinct epitopes . Other unique features of duck H3 antibodies included a convergent CDR H3-independent heavy chain-only binding mode and an N-glycosylated CDR H3 as decoy receptor . By annotating duck immunoglobulin germline genes , we also demonstrated the importance of gene conversion in duck H3 antibodies. Overall, our findings provide insights into how millennia of coevolution ha...

  Abstract We investigated the evolutionary history of the newly emergent neuraminidase (am4N1) associated with the D1.1 and D1.2 genotypes of highly pathogenic avian influenza A(H5N1) viruses in North America . Phylogenetic inference places am4N1 in a sister clade to Eurasian avian, swine, and human A(H1N1)pdm09 viruses and distinct from 1918, pre-2009 human seasonal, and classical swine A(H1N1) lineages . Am4N1 descends from diverse avian N1 genes endemic to the Americas. Phylodynamic analysis indicates a monophyletic am4N1 lineage with numerous introductions of viruses carrying the am4N1 gene likely originating from western Canada into the United States during emergence of the D1.1 and D1.2 genotypes. The lineage has diversified and accumulated deletions in the stalk domain . Despite amino acid divergence, structural modeling shows conserved neuraminidase architecture in the globular head . Given its distinct ancestry and amino acid sequence, further studies are needed to assess...

  Abstract A human infection with clade 2.3.4.4b H5N1 influenza A virus in Canada revealed minority variants E190D and Q226H in the hemagglutinin (HA) receptor-binding site (RBS). Because mutations at positions 190 and 226 have been associated with altered receptor specificity in other influenza subtypes, we investigated their impact on receptor binding in H5 HA . Using a recombinant protein approach and an ELISA-based glycan-binding assay , we assessed binding to representative avian- and human-type sialylated glycans . Both single mutations and their combination resulted in a complete loss of detectable binding to the tested glycans . To evaluate whether this phenotype was background-dependent, Q226H was additionally introduced into two other H5 HA proteins , each representing a distinct clade . In both cases, the mutation similarly abolished receptor binding . These findings independently validate recent glycan microarray observations and demonstrate that the patient-derived E19...

  Abstract Antibodies to the influenza hemagglutinin protein (HA) confer the strongest protection against infection . Immunity elicited by endemic, seasonal, human viruses is correlated with diminished disease severity and death caused by antigenically novel viruses. Antibodies to the HA head interface are broadly protective and abundant in human serologic and memory repertoires . Notably, few head interface antibodies from H5 naive donors are reported to bind H5 HAs . We find head interface antibodies engage a wide range of H5 isolates but fail to engage most isolates from the goose Guangdong (GsGd) lineage . We identify a single substitution, P221S, largely dictates antibody binding. Phylogenetic analysis indicates that P221S arose in a Chinese avian reservoir by the year 2000 . Descendants of these viruses have caused the current global panzootic and have achieved sustained mammal-mammal transmission in farmed and wild mammals. Our findings demonstrate that viral evolution in no...

  Abstract The H7N9 avian influenza virus (AIV) has posed a major global public health concern since its first detection in China in 2013 . Transmitted among wild birds and poultry , this virus has crossed the species barrier to infect humans , causing severe respiratory disease and high mortality . Although the widespread use of H7 vaccines has markedly reduced human infections , the ongoing circulation and adaptive evolution of the virus in poultry remain a serious threat . In this study, we analyzed three highly pathogenic H7N9 isolates collected in China in 2022, representing two hemagglutinin (HA) gene evolutionary lineages : Group.y.2.3 (isolate 229-4, chicken origin; isolate 782-2, quail origin) and Group.y.2.4 (isolate 621, quail origin). Pathogenicity was compared through phylogenetic analysis , molecular characterization, and infection experiments in both avian and mammalian models . Group.y.2.3 isolates displayed stronger replication and pathogenicity in chickens and mic...

  ABSTRACT The recent emergence of highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b, genotype B3.13) in dairy cattle presents substantial challenges to the agricultural sector and public health. Mechanistic studies of infection and transmission in cattle have proven difficult due to animal handling restrictions and the limited availability of established cell culture models. Primary bovine embryonic fibroblasts (BeEFs) were isolated and investigated here as a model to study influenza A virus (IAV) infection dynamics. We compared sialylation profiles , infectious virus production, viral replication, and plaque morphology in BeEFs following infection with the bovine HPAI H5N1 and an earlier 2.3.4.4b genotype (B1.1) isolated in 2022. The data presented here demonstrate increased expression of α-2,3 sialic acids compared to α-2,6 sialic acids in BeEFs , similar to sialylation profiles previously reported in bovine mammary tissue . These data also display increased viral fi...

  Abstract The recent emergence of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in U.S. dairy cattle marks a pivotal shift in the ecology of influenza A viruses (IAVs), signaling an unexpected expansion into a major livestock species . This review explores the molecular mechanisms underpinning this cross-species transmission , focusing on the unique sialic acid receptor landscape of the bovine mammary gland as a critical determinant. We synthesize emerging evidence that this tissue, which co-expresses both avian-type (α2,3-linked) and human-type (α2,6-linked) sialic acid receptors , functions as a novel biological crucible for viral adaptation . Within this environment, H5N1 virus faces selective pressure for hemagglutinin (HA) mutations —such as Q226L and N193D—that can alter receptor binding specificity toward human-like glycans , potentially bridging the species barrier. Recent studies confirm that bovine H5N1 virus isolates exhibit dual receptor-binding avidity ...

  ABSTRACT Swine influenza A virus (swIAV) is an important pathogen with regard to both the swine industry and public health . The pandemic A(H1N1) 2009 outbreak was caused by the swine-origin pandemic A(H1N1) 2009 [A(H1N1)pdm09] virus. Several reports have shown that several amino acid substitutions in the hemagglutinin (HA) antigenic sites can alter HA antigenicity. However, the impact of the amino acid deletion at position 155 on HA antigenicity remains unknown. In this study, we have isolated 11 samples of swIAVs from seven pig farms in Japan and found an amino acid deletion at position 155 of the HA region in one of the isolates of the H1N2 subtype . To examine the impact of this amino acid deletion on viral replication and HA antigenicity, we generated recombinant influenza A viruses possessing the H1 HA gene encoding either an artificial insertion or deletion of glycine at position 155. The growth kinetics of these recombinant viruses in two different cell lines demonstrated...

  Abstract B etween 2022 and 2025, highly pathogenic avian influenza viruses (HPAIVs) of clade 2.3.4.4b, including four distinct H5 Eurasian (EA) genotypes , were detected in wild birds and mammals in the Svalbard Archipelago and on the island of Jan Mayen . We describe their epidemiology and genomic characteristics to improve understanding of HPAIV occurrence and transmission in the High Arctic . The initial cases in 2022 occurred during summer and involved a glaucous gull (Larus hyperboreus) and great skuas (Stercorarius skua) on Svalbard and Jan Mayen , representing the first detections of HPAIVs in the High Arctic . Three HPAIV genotypes were identified: EA-2020-C (H5N1), EA-2021-AB (H5N1), and EA-2021-I ( H5N5 ). In 2023 , HPAIVs were detected in a broader range of bird species, and retrospectively in an Atlantic walrus reported by another research group (Odobenus rosmarus rosmarus). Genotypes identified in 2023 were EA-2020-C (H5N1), EA-2021-I ( H5N5 ), and EA-2022-BB (H5N1)....

  Abstract Background   Seasonal human influenza viruses can escape from antibody-mediated neutralization when amino acid changes occur in the hemagglutinin protein . Routine surveillance identified circulation of an A(H3N2) virus variant in the Netherlands with amino acid substitutions at hemagglutinin positions 158 and 189 . These amino acid positions were previously responsible for antigenic change of influenza A(H3N2) viruses and potentially lead to escape of this variant from vaccine-mediated immunity .  Aim   To characterize the emergence and antigenic properties of N158K and K189R double substitution virus variants .  Methods   We analyzed the geographical and temporal dynamics of the double-substitution variant using a phylogeographic approach and used hemagglutination inhibition assays and antigenic cartography methods to map its antigenic properties.  Results   A(H3N2) viruses carrying K189R were first detected in Guatemala in June 2024,...

  Abstract Influenza D virus (IDV), primarily found in livestock species, has demonstrated cross-species transmission potential , yet its threat to humans remains poorly understood . Here, we curated a panel of IDV isolates collected during field surveillance from 2011 to 2020 from swine and cattle to assess their ability to infect human airway cells as a proxy for zoonotic threat assessment. Using lung epithelial cell lines , primary well-differentiated airway epithelial cultures, and precision-cut lung slices , we demonstrated that IDV efficiently propagates in cells and tissues from the human respiratory tract , reaching titers comparable to human influenza A virus (IAV). Infection kinetics in primary porcine airway cultures and respiratory tissues mirrored those from human , suggesting similar infectivity across species. To define host responses to IDV infection, we evaluated innate immune sensing and downstream interferon signaling in human respiratory cells. IDV infection res...

  ABSTRACT The H1N1 influenza virus is a major pandemic and seasonal pathogen with a broad host range , posing a substantial threat to human health and underscoring the need for continuous surveillance . Wild birds , as natural reservoirs of avian influenza viruses (AIVs), carry H1N1 strains capable of reassorting with other influenza viruses, which can drive pandemic emergence. The global migration of wild birds facilitates the spread of these viruses, and their interactions with poultry increase the risk of cross-species transmission , further amplifying the public health threat. However, knowledge of H1N1 genetic diversity in wild birds remains limited. Database analysis shows 80% of avian-origin H1N1 isolates come from wild birds across over 40 countries , mainly in North America, Europe and Asia . This study characterized the molecular traits and genetic evolution of four H1N1 AIVs isolated from common teal and spot-billed ducks during 2019–2021 . Phylogenetic and sequence ana...

  Highlights •  74% pooled MERS-CoV seroprevalence in African dromedaries •  Highest MERS-CoV RNA incidence (15.3%) observed in juvenile dromedaries •  2.4% pooled MERS-CoV seroprevalence in camel -exposed humans •  African MERS-CoV clade C exhibits unique polymorphisms •  Clade-specific features might explain low MERS-CoV infection rates in Africa Abstract Objective We explored factors contributing to the low human MERS-CoV prevalence in Africa by assessing MERS-CoV epidemiological and genomic features. Methods We followed the PRISMA guidelines. We searched for articles on epidemiological and virological MERS-CoV characteristics in humans and camels in Africa until August 2025. We used a generalised linear mixed-effects model to calculate pooled proportions. We identified relevant polymorphisms in African MERS-CoV lineages compared with the prototypic EMC/2012 and contemporary Arabian MERS-CoV (clade B5). Results We included 53 articles, with 31 used in th...

  ABSTRACT Oropouche virus (OROV), a neglected arbovirus, has historically been considered a self-limiting infection associated with febrile illness . However, the recent surge in cases since late 2023 has been marked by atypical outcomes , highlighting its underestimated clinical impact . Gastrointestinal symptoms such as diarrhea have also been reported, but the prevalence and mechanistic insight remain largely elusive. Here, through a meta-analysis of 12 identified clinical studies , we revealed a pooled prevalence of diarrhea as 15% (95% CI, 10%–20%) among the Oropouche patient population. In primary human intestinal organoid-based experimental models , we demonstrated productive infection by both a recent patient isolate (OROV-2024) and a historical strain (Be An19991). This is shown by the accumulation of intracellular OROV RNA, release of infectious particles, and immunostaining of OROV glycoprotein Gc. Interestingly, OROV infection mildly triggered the expression of type II...

  Abstract Introduction Seasonal influenza causes significant global morbidity, mortality, and economic burden . Ongoing viral evolution can lead to vaccine mismatch and the emergence of antiviral resistance , highlighting the importance of genomic surveillance. The 2024–2025 influenza season was characterized by high incidence and increased hospitalizations. Methods We analyzed influenza A virus (IAV) genomes and clinical characteristics from the 2024–2025 season . Whole-genome sequencing was performed on 648 influenza A–positive clinical specimens collected between October 2024 and April 2025. Results Hemagglutinin (HA) sequences were recovered from 74.23% (481/648) of samples and used for subtyping and phylogenetic analysis. A(H1N1)pdm09 and A(H3N2) viruses co-circulated , representing 55.5% and 44.5% of cases, respectively. Among A(H1N1)pdm09 viruses, the HA1 substitution T120A , located near the Sa antigenic site , increased more than twofold compared with the prior season. Ci...

  Abstract Middle East respiratory syndrome coronavirus (MERS-CoV) is an emerging coronavirus that can cause zoonotic disease in humans with lethal severe viral pneumonia . Dromedary camels are the source of zoonotic infection. As of November 2025, MERS-CoV has resulted in a total of 2630 reported cases, 37% of these being fatal . The number of reported human cases has been on a decreasing trend since 2016 and reached a nadir during the COVID-19 pandemic . The reason for the reduction of cases is unclear and may be multifactorial. We hypothesized that mutations accumulating in the virus spike protein may have reduced zoonotic potential . Here, we investigate the impact of recently emerged virus spike-protein mutations on virus replication competence using pseudoviruses and replication-competent recombinant viruses. We found that virus spike variants detected in 2019 and some from 2023 show a reduced cell entry, lower viral replication and reduced fitness in human primary alveolar e...