Molecular epidemiology of astrovirus type 1 in Belém, Brazil, as an agent of infantile gastroenteritis, over a period of 18 years (1982-2000): identification of two possible new lineages.

Human astroviruses (HAstV) are worldwide recognized as important viral enteropathogens during childhood. This study aims to determine the incidence, genetic diversity and intertype variability of HAstV-1 in children less than 5 years of age enrolled in several studies conducted in Belém/Pará, and São Luís/Maranhão, Brazil, from December 1982 to May 2000. Using EIA and RT-PCR, an overall positivity of 6.1% (155/2.534) was achieved, of these, 140 were positive by RT-PCR. The analysis of a 348bp ORF2 fragment revealed that HAstV-1 was the predominant genotype (85/140, 60.7%) throughout the 18 years of study. Phylogenetic analysis was performed for 81 of these strains, and 76 (93.8%) were genetically classified as HAstV-1a. The remainder of strains (n=5) were assigned to possible new lineages, 1e and 1f. Four of these five strains were detected in 1983 and 1984, and the lineage 1a circulated during 10 consecutive years (1990/2000). Genome sequence variation was found among the HAstV-1 strains involving all lineages, but only five nucleotide changes translated into aminoacid changes over this period, suggesting that HAstV-1 was very stable. The data obtained in this study should be useful for further studies at molecular level, including improvement of disease surveillance based on molecular diagnostic tools, and vaccine development.

Prevalence of human astrovirus genotypes associated with acute gastroenteritis among children in Belém, Brazil.

Worldwide human astroviruses (HAstV) have increasingly been recognized as causative agents of viral gastroenteritis, mainly in infants and young children. The aim of this study was to assess the epidemiology and genotype diversity of HAstVs detected in children who participated in a trial in Belém, Brazil with the rhesus human reassortant rotavirus vaccine tetravalent (RRV-TV). From April/1990 to August/1992, 624 diarrheic stool samples were tested by enzyme immunoassay (EIA) for HAstV, with a positive rate of 4.0%. Reverse transcription-polymerase chain reaction (RT-PCR) was done in 129 samples (25 positive and 104 with twice the optical density (OD) value of negative control by EIA) being 33 positive. The overall positivity yielded by both methods was 5.4% (34/624). Genotyping of the 33 positive samples was done by type-specific RT-PCR and confirmed by sequence analysis. Phylogenetic analysis was performed using a 348-bp fragment of the ORF2 region of the capsid gene. HAstV-1 was the most prevalent, accounting for 45.5% of the isolates, followed by HAstV-2 (27.3%), HAstV-3 (12.1%), HAstV-4 (12.1%), and HAstV-6 (3.0%). The monthly distribution showed that HAstV-1 was predominant in the first year of study (May/1990 to May/1991) with highest prevalence in January/1991. HAstV-2 was predominant from July to November/1991 and HAstV-4 from September to October/1990. At 24 months of age, 30.6% of children had been infected by HAstV. The clinical symptoms registered during HAstV associated-diarrhea were usually mild. These data highlight the circulation of the different HAstV genotypes in Belém during the study period.