Molecular epidemiology of group A rotavirus in outpatient diarrhea infants and children in Chongqing, China, 2011-2015.

Human group A rotavirus (RVA) is the leading cause of acute viral gastroenteritis in children under 5 years old worldwide. The aim of this study was to investigate the genotype distribution of RVA in the Midwest of China. Sentinel-based surveillance of acute diarrhea was conducted at Children's Hospital of Chongqing Medical University from 2011 to 2015. RVA was tested by using enzyme-linked immunosorbent assays. The partial VP4 genes and VP7 genes of rotavirus were amplified and sequenced, and genotyping and phylogenetic analyses were performed. Among the 2236 stool specimens collected from children with acute gastroenteritis, 681 (30.46%) were positive for RVA. The majority of children (89.28%) who tested positive for RVA were children aged ≤2 years. The seasonal peak of RVA was in the winter. As for genotype, four strain combinations, G9P[8], G3P[8], G1P[8], and G2P[4] contributed to 75.62% (515/681) of the RVA-associated diarrhea cases. After a marked increase in G9P[8] (30.77%) in 2013, G9P[8] became the predominant genotype in 2014 and 2015, whilst the prevalence of G1P[8] was decreased to 2.72% in 2015. Unusual G-P combinations (eg, G1P[4], G9P[4], G4P[6], G3P[4], G2P[8]) were also detected sporadically over the study period. Phylogenetic tree analysis results showed that the VP7 sequences of G9 strains were clustered into two main lineages, and 77.34% of them were clustered into lineage VI, with the highest nucleotide similarity to the strain JS12-17(China). VP4 gene sequences of P[8] strains were almost P[8]-lineage 3. Substantial temporal variation in the circulation of various genotypes of rotavirus in Chongqing was observed during 2011-2015, and highlights the need for continuous surveillance of RVA infection for better understanding and control of RVA infection.