Complete genome sequence of a highly divergent astrovirus isolated from a child with acute diarrhea

BACKGROUND: Astroviruses infect a variety of mammals and birds and are causative agents of diarrhea in humans and other animal hosts. We have previously described the identification of several sequence fragments with limited sequence identity to known astroviruses in a stool specimen obtained from a child with acute diarrhea, suggesting that a novel virus was present. RESULTS: In this study, the complete genome of this novel virus isolate was sequenced and analyzed. The overall genome organization of this virus paralleled that of known astroviruses, with 3 open reading frames identified. Phylogenetic analysis of the ORFs indicated that this virus is highly divergent from all previously described animal and human astroviruses. Molecular features that are highly conserved in human serotypes 1–8, such as a 3'NTR stem-loop structure and conserved nucleotide motifs present in the 5'NTR and ORF1b/2 junction, were either absent or only partially conserved in this novel virus. CONCLUSION: Based on the analyses described herein, we propose that this newly discovered virus represents a novel species in the family Astroviridae. It has tentatively been named Astrovirus MLB1.