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Astroviruses (AstVs) are major causative agents of gastroenteritis in children and have been reported in many species. Canine astrovirus (CaAstV), as an enteric pathogen, has been widely detected worldwide, but little is known about their genetic diversity and evolution, partly owing to a lack of genomic data. Here, we sequenced 12 nearly full‐length CaAstV genomes to address the gap in knowledge. We found 14 (13.2%) and 7 (3.35%) CaAstV‐positive samples from pet dogs with and without diarrhoea, respectively. Co‐infections were with co‐infection with Torque teno canis virus (TTCaV) reported for the first time. Phylogenetic analysis of the ORF2 gene revealed four major lineages. In particular, lineage 4 might have evolved from a recombinant virus from lineage 2 and lineage 3. The strains sequenced here clustered with lineages 2, 3 and 4 in contrast with other Chinese strains identified previously that clustered with lineages 2 and 4. Amino acid sequence alignment within lineage revealed intralineage amino acid diversity and that the type of epidemic strains within lineages changes over time. Three amino acids substitutions located in predicted B‐cell epitopes, which might be involved escape of host immunity. Moreover, frequent inter‐clade ORF2 gene recombinants were identified. The identification of individual recombination events and a recombinant lineage indicated that recombination plays a crucial role in CaAstV genetic evolution and diversity by generating divergent viruses. Moreover, phylogenetic analysis of ORF1b, the most conserved gene of astrovirus, revealed a close relationship between CaAstV and California sea lion astroviruses. Overall, we report detailed information on the genetic evolution and diversity of CaAstV, which indicates that CaAstV may pose challenges for diagnostics and future control strategies. [ABSTRACT FROM AUTHOR]

The newly emerged lineage 1 porcine reproductive and respiratory syndrome viruses (PRRSVs) (especially the NADC30‐like and NADC34‐like viruses) have posed a direct threat to the Chinese pig industry since 2013. The phylogenetic, epidemic, and recombinant properties of these viruses have not yet systematically analysed in China. This report presents regular surveillance and field epidemiological studies for PRRSV across China from 2007 to 2019. From over 4,000 detected clinical samples, 70 open reading frame five sequences and four complete genomes of lineage 1 viruses were successfully obtained. Combined with global data, we conducted an extensive and systematic molecular phylogeny analysis using a maximum likelihood tree. The Chinese lineage 1 viruses were clustered, and their temporal and spatial distribution was further explored. Multiple viral introductions of lineage 1 virus from the United States to China were detected, and some became endemic in China. There are three sub‐lineage 1 clusters: lineage 1.5 (NADC34‐like), lineage 1.6 and New Intro cluster (NADC30‐like). These viruses show high genetic diversity and a wide distribution in China, with Henan Province showing the highest diversity. Moreover, Chinese lineage 1 viruses have developed an endemic NADC30‐like cluster. The demographic feature of this cluster showed a more or less constant population expansion history with a recent decreasing trend. Moreover, the genome recombination of Chinese lineage 1 with two dominant clusters (Chinese HP‐PRRSVs: lineage 8.7 and VR2332‐like: lineage 5.1) was frequently detected, both of which have commercial vaccine strains available. Furthermore, recombination hotspots were discovered near NSP9 and ORF2‐4 regions of the genome. Overall, these findings provide important insights into the evolution and geographical diversity of Chinese lineage 1 PRRSV. These results will facilitate the development of programmes for the control and prevention of the emerging lineage 1 viruses in China. [ABSTRACT FROM AUTHOR]