The incidence of astrovirus infection was determined among infants and young children admitted to Alice Springs Hospital (central Australia) with gastroenteritis from 1995 to 1998. Astrovirus was detected by reverse transcription-PCR in 33 of 495 stool samples, and this represented 4.3% of a total of 774 stool samples tested for astrovirus, rotavirus, and Norwalk-like viruses. Astrovirus incidence was substantially lower than that of rotavirus but higher than that of Norwalk-like viruses both overall and in each of the 4 years individually. Over the period from 1981 to 1998, including the period from 1981 to 1994 during which astrovirus was identified only by electron microscopy, astrovirus serotypes (deduced from genotypes) 1, 2, 3, and 4 were identified. Deduced serotypes 1, 3, and 4 all appeared regularly over this 18-year period. Also over this period, nucleotide variation (in some cases substantial) in a section of the capsid protein precursor region of the virus genome was evident among strains of all four of the deduced central Australian serotypes. Consequent amino acid changes were, however, only evident among deduced serotype 3 strains. Geographic variation at both the genome and the resultant amino acid levels was evident among strains of all four of the deduced central Australian serotypes and their respective prototypes isolated in the United Kingdom.

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