ANNUAL INCIDENCE, SEROTYPE DISTRIBUTION, AND GENETIC DIVERSITY OF HUMAN ASTROVIRUS ISOLATES FROM HOSPITALIZED CHILDREN IN MELBOURNE, AUSTRALIA

The incidence of astrovirus infection in children under 5 years of age hospitalized for acute gastroenteritis in Melbourne, Australia, durin g 1995 was determined. Astrovirus was detected in 16 fecal specimens b y Northern (RNA) dot blot analysis of RNA isolated from feces with an astrovirus-specific cDNA probe. The incidence of astrovirus infection was determined as 4.2% (16 of 378 total samples) compared with rates o f 63.2, 3.7, and 4.2% for rotavirus, adenovirus, and all bacterial pat hogens, respectively. Astrovirus was detected during the winter season and mainly in infants between 6 and 12 months of age. Serotyping of s amples was carried out by reverse transcriptase PCR and direct sequenc ing of a 348-bp region of the capsid protein gene. Type 1 strains pred ominated (11 of 13 typeable samples), although type 4 isolates were al so detected, Astrovirus was retrospectively identified in 13 fecal sam ples collected from hospitalized infants between 1980 and 1985 and sho wn to contain small viruses by electron microscopy. Type 1 isolates we re again the most common, although a type 5 strain was also found. Com parative sequence analysis indicated that type 1 astroviruses exhibite d up to 7% sequence divergence over a 15-year period; however, all mut ations were silent. The incidence of astrovirus reported here indicate s that the virus is a significant cause of severe diarrhea in young ch ildren. The genetic analysis also provides important molecular epidemi ological information relevant to the development of preventative thera pies.