Prevalence and genomic variation of Norwalk-like viruses in central Australia in 1995-1997.

Norwalk-like viruses (NLVs) have now been found to be important causes of gastroenteritis amongst infants and young children as well as older children and adults. Although detected, such viruses appeared not to be a major cause amongst infants and young children hospitalized with gastroenteritis in Alice Springs, central Australia over the period January 1995-December 1997. Nine NLV-positive cases were identified amongst stools from 360 different patients. From the nine cases however, eight different NLV strains were identified from comparisons of the sequence of a section of the RNA polymerase gene, and a high degree of genomic diversity was evident amongst them. In general, these strains were more similar to those identified in other countries than to those identified in central Australia over the three year period. Of the strains identified, six (and most probably seven) were classified in genogroup I, while only one was classified in genogroup II. This predominance of genogroup I strains is in contrast to most of the more recent findings made elsewhere, including those made in other parts of Australia. Phylogenetic analysis indicated that the central Australian strains spanned a range of known representative NLV strains, with one of the genogroup I strains showing a 96% nucleotide identity to Saratoga virus.