HUMAN ENTERIC CALICIVIRUSES HAVE A UNIQUE GENOME STRUCTURE AND ARE DISTINCT FROM THE NORWALK-LIKE VIRUSES

Classic human enteric caliciviruses (HuCVs) have a distinctive morphol ogy and are primarily associated with pediatric acute gastroenteritis. Although morphologically distinct from the small round structured vir uses (SRSVs), the classic HuCVs are thought to be closely related and were anticipated to have a similar genome organisation. We report the first genome sequence and molecular characterisation of a classic huma n enteric calicivirus associated with a case of acute vomiting and dia rrhoea in an infant. The RNA genome (7266 nt) is smaller than the geno me of SRSVs from the two genetic groups and has a unique arrangement o f open reading frames. Further analysis of the 3' terminal 3 kb from a second unrelated isolate confirmed this genomic organisation. Analysi s of capsid and RNA polymerase sequences together with the unique geno mic organisation of classic HuCV suggest these viruses are more closel y related to the animal caliciviruses than the enteric SRSV group of v iruses.