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.