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Since 2018, the outbreaks of genotype II African swine fever virus (ASFV) in China and several eastern Asian countries have caused a huge impact on the local swine industry, resulting in huge economic losses. However, little is known about the origin, genomic diversity, evolutionary features, and epidemiological history of the genotype II ASFV. Here, 14 high-quality complete genomes of ASFVs were generated via sequencing of samples collected from China over the course of 3 years, followed by phylogenetic and phylodynamic analyses. The strains identified were relatively homogeneous, with a total of 52 SNPs and 11 indels compared with the prototype strain HLJ/2018, among which there were four exceptionally large deletions (620–18,023 nt). Evolutionary analyses revealed that ASFV strains distributed in eastern Asia formed a monophyly and a 'star-like' structure centered around the prototype strain, suggesting a single origin. Additionally, phylogenetic network analysis and ancestral reconstruction of geographic state indicated that genotype II ASFV strains in eastern Asia likely originated from Western Europe. Overall, these results contribute to the understanding of the history and current status of genotype II ASFV strains in eastern Asian, which could be of considerable importance in disease control and prevention. [ABSTRACT FROM AUTHOR]

Cats harbor many important viral pathogens, and the knowledge of their diversity has been greatly expanded thanks to increasingly popular molecular sequencing techniques. While the diversity is mostly described in numerous regionally defined studies, there lacks a global overview of the diversity for the majority of cat viruses, and therefore our understanding of the evolution and epidemiology of these viruses was generally inadequate. In this study, we analyzed 12,377 genetic sequences from 25 cat virus species and conducted comprehensive phylodynamic analyses. It revealed, for the first time, the global diversity for all cat viruses known to date, taking into account highly virulent strains and vaccine strains. From there, we further characterized and compared the geographic expansion patterns, temporal dynamics and recombination frequencies of these viruses. While respiratory pathogens such as feline calicivirus showed some degree of geographical panmixes, the other viral species are more geographically defined. Furthermore, recombination rates were much higher in feline parvovirus, feline coronavirus, feline calicivirus and feline foamy virus than the other feline virus species. Collectively, our findings deepen the understanding of the evolutionary and epidemiological features of cat viruses, which in turn provide important insight into the prevention and control of cat pathogens. [ABSTRACT FROM AUTHOR]

SARS-CoV-2, which causes the current pandemic of respiratory illness, is evolving continuously and generating new variants. Nevertheless, most of the sequence analyses thus far focused on nucleotide substitutions despite the fact that insertions and deletions (indels) are equally important in the evolution of SARS-CoV-2. In this study, we analyzed 1,099,664 high-quality sequences of SARS-CoV-2 genomes to re-construct the evolutionary and epidemiological histories of indels. Our analysis revealed 289 circulating indel types (237 deletion and 52 insertion types, each represented by more than ten genomic sequences), among which eighteen were recurrent indel types, each represented by more than 500 genome sequences. Although indels were identified across the entire genome, most of them were identified in nsp6, S, ORF8, and N genes, among which ORF8 indel types had the highest frequencies of frameshift. Geographical and temporal analyses of these variants revealed a few alterations of dominant indel types, each accompanied by geographic expansion to different countries and continents, which resulted in the fixation of several types of indels in the field, including the current variants of concern. Evolutionary and structural analyses revealed that indels involving S N-terminal domain regions were linked to the 3/4 variants of concern, resulting in significantly altered S protein that might contribute to the selective advantage of the corresponding variant. In sum, our study highlights the important role of insertions and deletions in the evolution and spread of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

Despite the ongoing interest in virus discovery, little is known about the factors that shape communities of viruses within individual hosts. Here, we address how virus communities might be impacted by the age of the hosts they infect, using total RNA sequencing to reveal the RNA viromes of different age groups of Ruddy Turnstones (Arenaria interpres). From oropharyngeal and cloacal swabs we identified 14 viruses likely infecting birds, 11 of which were novel, including members of the Reoviridae , Astroviridae , and Picornaviridae. Strikingly, 12 viruses identified were from juvenile birds sampled in the first year of their life, compared to only two viruses in adult birds. Both viral abundance and alpha diversity were marginally higher in juvenile than adult birds. As well as informing studies of virus ecology, that host age might be associated with viral composition is an important consideration for the future surveillance of novel and emerging viruses. • Virus diversity and community structure in wild birds is largely unknown. • We reveal 14 viral species in Ruddy Turnstones sampled in Australia. • Virus abundance and diversity is higher in juvenile birds compared to adults. • Virus communities differ across time, suggesting the RNA virome is transient. [ABSTRACT FROM AUTHOR]

The Tasmanian devil is an endangered carnivorous marsupial threatened by devil facial tumour disease DFTD). While research on DFTD has been extensive, little is known about viruses in devils, and whether any are of potential conservation relevance for this endangered species. Using both metagenomics based on virion enrichment and sequence-independent amplification (virion-enriched metagenomics) and meta-transcriptomics based on bulk RNA sequencing, we characterized and compared the fecal viromes of captive and wild devils. A total of 54 fecal samples collected from 2 captive and 4 wild populations were processed for virome characterization using both approaches. In total, 24 novel marsupial-related viruses, comprising a sapelovirus, astroviruses, rotaviruses, picobirnaviruses, parvoviruses, papillomaviruses, polyomaviruses and a gammaherpesvirus were identified, as well as known mammalian pathogens such as rabbit haemorrhagic disease virus 2. Captive devils showed significantly lower viral diversity than wild devils. Comparison of the two virus discovery approaches revealed substantial differences in the number and types of viruses detected, with meta-transcriptomics better suited for RNA viruses and virion-enriched metagenomics largely identifying more DNA viruses. Thus, the viral communities revealed by virion-enriched metagenomics and meta-transcriptomics were not interchangeable and neither approach was able to detect all viruses present. An integrated approach using both virion-enriched metagenomics and meta-transcriptomics constitutes a powerful tool for obtaining a complete overview of both the taxonomic and functional profiles of viral communities within a sample. Importance: The Tasmanian devil is an iconic Australian marsupial that has suffered an 80% population decline due to a contagious cancer, devil facial tumour disease, along with other threats. Until now, viral discovery in this species has been confined to one gammaherpesvirus (DaHV-2), for which captivity was identified as a significant risk factor. Our discovery of 24 novel marsupial-associated RNA and DNA viruses, and that viral diversity is lower in captive than wild devils, has greatly expanded our knowledge of gut-associated viruses in devils and provides important baseline information that will contribute to the conservation and captive management of this endangered species. Our results also revealed that a combination of virion-enriched metagenomics and meta-transcriptomics may be a more comprehensive approach for virome characterization than either method alone. Our results thus provide a springboard for continuous improvements in the way we study complex viral communities. [ABSTRACT FROM AUTHOR]

Metagenomics is transforming the study of virus evolution, allowing the full assemblage of virus genomes within a host sample to be determined rapidly and cheaply. The genomic analysis of complete transcriptomes, so-called meta-transcriptomics, is providing a particularly rich source of data on the global diversity of RNA viruses and their evolutionary history. Herein we review some of the insights that meta-transcriptomics has provided on the fundamental patterns and processes of virus evolution, with a focus on the recent discovery of a multitude of novel invertebrate viruses. In particular, meta-transcriptomics shows that the RNA virus world is more fluid than previously realized, with relatively frequent changes in genome length and structure. As well as having a transformative impact on studies of virus evolution, meta-transcriptomics presents major new challenges for virus classification, with the greater sampling of host taxa now filling many of the gaps on virus phylogenies that were previously used to define taxonomic groups. Given that most viruses in the future will likely be characterized using metagenomics approaches, and that we have evidently only sampled a tiny fraction of the total virosphere, we suggest that proposals for virus classification pay careful attention to the wonders unearthed in this new age of virus discovery. [ABSTRACT FROM AUTHOR]

Abstract: The emergence and spread of Type 2 Porcine Reproductive and Respiratory Syndrome virus (Type 2 PRRSV) in North America is heavily influenced by the multiple site production system used in the hog industry. However, it is unclear how anthropogenic factors such has this have shaped the current spatial distribution of PRRSV genotypes. We employed Bayesian phylogeographic analyses of 7040 ORF5 sequences to reveal the recent geographical spread of Type 2 PRRSV in North America. The directions and intensities in our inferred virus traffic network closely mirror the hog transportation. Most notably, we reveal multiple viral introductions from Canada into the United States causing a major shift in virus genetic composition in the Midwest USA that went unnoticed by the regular surveillance and field epidemiological studies. Overall, these findings provide important insights into the dynamics of Type 2 PRRSV evolution and spread that will facilitate programs for control and prevention. [Copyright &y& Elsevier]

Understanding how pathogens invade and become established in novel host populations is central to the ecology and evolution of infectious disease. Influenza viruses provide unique opportunities to study these processes in nature because of their rapid evolution, extensive surveillance, large data sets and propensity to jump species boundaries. H5N1 highly pathogenic avian influenza virus (HPAIV) is a major animal pathogen and public health threat. The virus is of particular importance in Indonesia, causing severe outbreaks among poultry and sporadic human infections since 2003. However, little is known about how H5N1 HPAIV emerged and established in Indonesia. To address these questions, we analysed Indonesian H5N1 HPAIV gene sequences isolated during 2003-2007. We find that the virus originated from a single introduction into East Java between November 2002 and October 2003. This invasion was characterized by an initially rapid burst of viral genetic diversity followed by a steady rate of lineage replacement and the maintenance of genetic diversity. Several antigenic sites in the haemagglutinin gene were subject to positive selection during the early phase, suggesting that host-immune-driven selection played a role in host adaptation and expansion. Phylogeographic analyses show that after the initial invasion of H5N1, genetic variants moved both eastwards and westwards across Java, possibly involving long-distance transportation by humans. The phylodynamics we uncover share similarities with other recently studied viral invasions, thereby shedding light on the ecological and evolutionary processes that determine disease emergence in a new geographical region. [ABSTRACT FROM AUTHOR]

Abstract: Since its first discovery two decades ago, porcine reproductive and respiratory syndrome virus (PRRSV) has been the subject of intensive research due to its huge impact on the worldwide swine industry. Thanks to the phylogenetic analyses, much has been learned concerning the genetic diversity and evolution history of the virus. In this review, we focused on the evolutionary and epidemiological aspects of PRRSV from a phylogenetic perspective. We first described the diversity and transmission dynamics of Type 1 and 2 PRRSV, respectively. Then, we focused on the more ancient evolutionary history of PRRSV: the time of onset of all existing PRRSV and an origin hypothesis were discussed. Finally, we summarized the results from previous recombination studies to assess the potential impact of recombination on the virus epidemiology. [ABSTRACT FROM AUTHOR]

Astroviruses, isolated from numerous avian and mammalian species including humans, are commonly associated with enteritis and encephalitis. Two astroviruses have previously been identified in cats, and while definitive evidence is lacking, an association with enteritis is suggested. Using metagenomic next-generation sequencing of viral nucleic acids from faecal samples, we identified two novel feline astroviruses termed Feline astrovirus 3 and 4. These viruses were isolated from healthy shelter-housed kittens (Feline astrovirus 3; 6448 bp) and from a kitten with diarrhoea that was co-infected with Feline parvovirus (Feline astrovirus 4, 6549 bp). Both novel astroviruses shared a genome arrangement of three open reading frames (ORFs) comparable to that of other astroviruses. Phylogenetic analysis of the concatenated ORFs, ORF1a, ORF1b and capsid protein revealed that both viruses were phylogenetically distinct from other feline astroviruses, although their precise evolutionary history could not be accurately determined due to a lack of resolution at key nodes. Large-scale molecular surveillance studies of healthy and diseased cats are needed to determine the pathogenicity of feline astroviruses as single virus infections or in co-infections with other enteric viruses. [ABSTRACT FROM AUTHOR]

Tilapia lake virus (TiLV) has caused mass mortalities in farmed and wild tilapia with serious economic and ecological consequences. Until recently, this virus was the sole member of the Amnoonviridae, a family within the order Articulavirales comprising segmented negative-sense RNA viruses. We sought to identify additional viruses within the Amnoonviridae through total RNA sequencing (meta-transcriptomics) and data mining of published transcriptomes. Accordingly, we sampled marine fish species from both Australia and China and discovered several segments of two new viruses within the Amnoonviridae, tentatively called Flavolineata virus and Piscibus virus, respectively. In addition, by mining vertebrate transcriptome data, we identified nine additional virus transcripts matching to multiple genomic segments of TiLV in both marine and freshwater fish. These new viruses retained sequence conservation with the distantly related Orthomyxoviridae in the RdRp subunit PB1, but formed a distinct and diverse phylogenetic group. These data suggest that the Amnoonviridae have a broad host range within fish and that greater animal sampling will identify additional divergent members of the Articulavirales. [ABSTRACT FROM AUTHOR]

Despite their ecological importance, nothing is known about the diversity and abundance of RNA viruses in termites (Termitoidae). We used a metatranscriptomics approach to determine the RNA virome structure of 50 diverse species of termite that differ in both phylogenetic position and colony composition. From these samples, we identified 67 novel RNA viruses, characterized their genomes, quantified their abundance and inferred their evolutionary history. These viruses were found within or similar to those from the Togaviridae, Iflaviridae, Polycipiviridae, Flaviviridae, Leviviridae, Narnaviridae, Mitoviridae, Lispivirdae, Phasmaviridae, Picobirnaviridae and Partitiviridae. However, all viruses identified were novel and divergent, exhibiting only 20% to 45% amino acid identity to previously identified viruses. Our analysis suggested that 17 of the viruses identified were termite-infecting, with the remainder likely associated with the termite microbiome or diet. Unclassified sobemo-like and bunya-like viruses dominated termite viromes, while most of the phylogenetic diversity was provided by the picobirna- and mitovirus-like viruses. Of note was the identification of a novel flavi-like virus most closely related to those found in marine vertebrates and invertebrates. Notably, the sampling procedure had the strongest association with virome composition, with greater RNA virome diversity in libraries prepared from whole termite bodies than those that only sampled heads. [ABSTRACT FROM AUTHOR]

DNA viruses comprise a wide array of genome structures and infect diverse host species. To date, most studies of DNA viruses have focused on those with the strongest disease associations. Accordingly, there has been a marked lack of sampling of DNA viruses from invertebrates. Bulk RNA sequencing has resulted in the discovery of a myriad of novel RNA viruses, and herein we used this methodology to identify actively transcribing DNA viruses in meta-transcriptomic libraries of diverse invertebrate species. Our analysis revealed high levels of phylogenetic diversity in DNA viruses, including 13 species from the Parvoviridae, Circoviridae, and Genomoviridae families of single-stranded DNA virus families, and six double-stranded DNA virus species from the Nudiviridae, Polyomaviridae, and Herpesviridae, for which few invertebrate viruses have been identified to date. By incorporating the sequence of a "blank" experimental control we also highlight the importance of reagent contamination in metagenomic studies. In sum, this work expands our knowledge of the diversity and evolution of DNA viruses and illustrates the utility of meta-transcriptomic data in identifying organisms with DNA genomes. [ABSTRACT FROM AUTHOR]

Mosquitoes harbor an extensive diversity of 'insect-specific' RNA viruses in addition to those important to human and animal health. However, because most studies of the mosquito virome have been conducted at lower latitudes, little is known about the diversity and evolutionary history of RNA viruses sampled from mosquitoes in northerly regions. Here, we compared the RNA virome of two common northern mosquito species, Culex pipiens and Culex torrentium, collected in south-central Sweden. Following bulk RNA-sequencing (meta-transcriptomics) of 12 libraries, comprising 120 specimens of Cx. pipiens and 150 specimens of Cx. torrentium, we identified 40 viruses (representing 14 virus families) of which 28 were novel based on phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) protein. Hence, we documented similar levels of virome diversity as in mosquitoes sampled from the more biodiverse lower latitudes. Many viruses were also related to those sampled on other continents, indicative of a widespread global movement and/or long host–virus co-evolution. Although the two mosquito species investigated have overlapping geographical distributions and share many viruses, several viruses were only found at a specific location at this scale of sampling, such that local habitat and geography may play an important role in shaping viral diversity in Culex mosquitoes. [ABSTRACT FROM AUTHOR]

Hepatitis delta virus (HDV) is the smallest known RNA virus, encoding a single protein. Until recently, HDV had only been identified in humans, where it is strongly associated with co-infection with hepatitis B virus (HBV). However, the recent discovery of HDV-like viruses in metagenomic samples from birds and snakes suggests that this virus has a far longer evolutionary history. Herein, using additional meta-transcriptomic data, we show that highly divergent HDV-like viruses are also present in fish, amphibians, and invertebrates, with PCR and Sanger sequencing confirming the presence of the invertebrate HDV-like viruses. Notably, the novel viruses identified here share genomic features characteristic of HDV, such as a circular genome of only approximately 1.7 kb in length, and self-complementary, unbranched rod-like structures. Coiled-coil domains, leucine zippers, conserved residues with essential biological functions, and isoelectronic points similar to those in the human hepatitis delta virus antigens (HDAgs) were also identified in the putative non-human viruses. Importantly, none of these novel HDV-like viruses were associated with hepadnavirus infection, supporting the idea that the HDV–HBV association may be specific to humans. Collectively, these data not only broaden our understanding of the diversity and host range of HDV, but also shed light on its origin and evolutionary history. [ABSTRACT FROM AUTHOR]

Our knowledge of mammalian viruses has been strongly skewed toward those that cause disease in humans and animals. However, recent metagenomic studies indicate that most apparently healthy organisms carry viruses, and that these seemingly benign viruses may comprise the bulk of virus diversity. The bias toward studying viruses associated with overt disease is apparent in the lagoviruses (family Caliciviridae) that infect rabbits and hares: although most attention has been directed toward the highly pathogenic members of this genus—rabbit haemorrhagic disease virus and European brown hare syndrome virus—a number of benign lagoviruses have also been identified. To determine whether wild European brown hares in Australia might also carry undetected benign viruses, we used a meta-transcriptomics approach to explore the gut and liver RNA viromes of these invasive animals. This led to the discovery of three new lagoviruses. While one was only detected in a single hare, the other two viruses were detected in 20 per cent of all animals tested. All three viruses were most closely related to other hare lagoviruses, but were phylogenetically distinct from both known viruses and from each other, indicating that lagoviruses have circulated for longer than previously assumed. Their evolution was also characterised by complex recombination events. Mapping mutations onto the lagovirus phylogeny revealed no amino acid changes that were consistently associated with virulence phenotype. Overall, our study points to extensive unsampled diversity in this genus, such that additional metagenomic studies are needed to fill gaps in the lagovirus phylogeny and better understand the evolutionary history of this important group of mammalian viruses. [ABSTRACT FROM AUTHOR]

Abstract: Severe Acute Respiratory Syndrome (SARS) is a respiratory disease caused by a zoonotic coronavirus (CoV) named SARS-CoV (SCoV), which rapidly swept the globe after its emergence in rural China during late 2002. The origins of SCoV have been mysterious and controversial, until the recent discovery of SARS-like CoV (SLCoV) in bats and the proposal of bats as the natural reservior of the Coronaviridae family. In this article, we focused on discussing how phylogenetics contributed to our understanding towards the emergence and transmission of SCoV. We first reviewed the epidemiology of SCoV from a phylogenetic perspective and discussed the controversies over its phylogenetic origins. Then, we summarized the phylogenetic findings in relation to its zoonotic origins and the proposed inter-species viral transmission events. Finally, we also discussed how the discoveries of SCoV and SLCoV expanded our knowledge on the evolution of the Coronaviridae family as well as its implications on the possible future re-emergence of SCoV. [Copyright &y& Elsevier]

Live poultry markets (LPMs) are an important source of novel avian influenza viruses (AIV). During 2015–2016 we surveyed AIV diversity in ten LPMs in Hubei, Zhejiang and Jiangxi provinces, China. A high diversity and prevalence of AIVs (totaling 12 subtypes) was observed in LPMs in these provinces. Strikingly, however, the subtypes discovered during 2015–2016 were markedly different to those reported by us in these same localities one year previously, suggesting a dynamic shift in viral genetic diversity over the course of a single year. Phylogenetic analyses revealed frequent reassortment, including between high and low pathogenic AIV subtypes and among those that circulate in domestic and wild birds. Notably, the novel H5N6 reassortant virus, which contains a set of H9N2-like internal genes, was prevalent in all three regions surveyed. Overall, these data highlight the profound changes in genetic diversity and in patterns of reassortment in those AIVs that circulate in LPMs. [ABSTRACT FROM AUTHOR]

Rotaviruses are an important cause of severe diarrheal illness in children globally. We characterized rotaviruses sampled in humans, insectivores (shrews) and rodents from urban and rural regions of Zhejiang province, China. Phylogenetic analyses revealed seven genotypic constellations of human rotaviruses with six different combinations of G and P genotypes – G3P[8] (50.06%), G9P[8] (36.16%), G1P[8] (8.92%), G2P[4] (4.63%), G3P[3] (0.12%), and G3P[9] (0.12%). In rodents and shrews sampled from the same locality we identified a novel genotype constellation (G32-P[46]-I24-R18-C17-M17-A28-N17-T19-E24-H19), a novel P genotype (P[45]), and two different AU-1-like rotaviruses associated with a G3P[3] genotype combination. Of particular note was a novel rotavirus from a human patient that was closely related to viruses sampled from rodents in the same region, indicative of a local species jump. In sum, these data are suggestive of the cross-species transmission of rodent rotaviruses into humans and for reassortment among human and animal rotaviruses. [ABSTRACT FROM AUTHOR]

Although rodents are important reservoirs for RNA viruses, to date only one species of rodent coronavirus (CoV) has been identified. Herein, we describe a new CoV, denoted Lucheng Rn rat coronavirus (LRNV), and novel variants of two Betacoronavirus species termed Longquan Aa mouse coronavirus (LAMV) and Longquan Rl rat coronavirus (LRLV), that were identified in a survey of 1465 rodents sampled in China during 2011–2013. Phylogenetic analysis revealed that LAMV and LRLV fell into lineage A of the genus Betacoronavirus , which included CoVs discovered in humans and domestic and wild animals. In contrast, LRNV harbored by Rattus norvegicus formed a distinct lineage within the genus Alphacoronavirus in the 3CL pro , RdRp, and Hel gene trees, but formed a more divergent lineage in the N and S gene trees, indicative of a recombinant origin. Additional recombination events were identified in LRLV. Together, these data suggest that rodents may carry additional unrecognized CoVs. [ABSTRACT FROM AUTHOR]