Detection of Norwalk-like virus genes in the caecum contents of pigs.

Norwalk-like virus genes were detected by RT-PCR in the caecum contents of pigs. Positive PCR products were produced from four out of 1 117 samples by nested PCR using human SRSV primers. Nucleotide sequences between 4 561 and 4 852 numbered according to the Norwalk virus genomic RNA in the RNA polymerase region were determined. Between the Norwalk virus sequence and the sequences detected in pigs, there was 58.2% to 59.9% sequence homology. The swine sequences were located on genogroup II of human SRSVs, but formed a subgroup in the phylogenetic tree of caliciviruses.