Recombination analysis based on the HAstV-2 and HAstV-4 complete genomes

•Full genomes of four HAstV strains from Novosibirsk were sequenced.•Analysis of the recombination events has detected potential breakpoints.•The evolutionary chronology of HAstV genotypes has been reconstructed. Complete genome sequences of previously unstudied human astrovirus subgenotypes – HAstV-2a and HAstV-2c – and two isolates of a rare genotype HAstV-4 have been determined. These isolates were recovered from fecal samples of young children hospitalized with acute intestinal infections in Novosibirsk (Russia). Three of the four sequenced isolates (HAstV-2a, HAstV-2c, and HAstV-4) are recombinants. It has been shown that all known HAstV-2 genomes have emerged via recombination; the HAstV-1 and HAstV-4 genotypes contain both recombinant and non-recombinant isolates; and all HAstV-3, HAstV-5, and HAstV-6 whole-genome sequences display no reliable signs of recombination. The average mutation accumulation rate has been determined based on an extended ORF2 fragment and amounts to 1.0×10−3 substitutions per site per year. The evolutionary chronology of current HAstV genotypes has been reconstructed.