3.4 Distribution of P Genotype of RVA
Among 246 RVA-positive samples, 245 samples were successfully genotyped based on the partial VP4 region. Considering the distribution of P genotypes, four P genotypes (P[4], P[6], P[8], and P[10]) were identified from 2020 to 2022. P[8] remained the undisputed most prevalent genotype circulating in Shanghai, with proportions of 95.5% (21/22), 95.9% (141/147), and 100.0% (77/77) from 2020 to 2022, respectively. In addition, the other three P genotypes (P[4], P[6], and P[10]) were rarely present only in 2021(Figure 3B).
3.5 Distribution ofG/P Genotype of RVA
Regarding G/P combinations, 13 different RVA genotypes were detected with different frequencies in this study. Overall, G9P[8] (45.5%, 112/246) was the most predominant RVA strain, followed by G8P[8] (37.4%, 92/246) and G3P[8] (4.1%, 10/246). Some other uncommon strains such as G1P[8], G1P[10], G2P[8], G4P[8], G6P[8], G9P[4], and G9P[6] were detected very rarely and accounted for a total of 6.1% (15/246) of the total genotyped strains. Notably, partially genotyped and un-genotyped RVA strains were detected at a low frequency (6.9%, 17/246).
However, the circulation of G/P combinations varied from 2020 to 2022. G9P[8] was the most circulating genotype in 2020 (68.2%, 15/22) and 2021 (57.8%, 85/147), while G8P[8] (68.8%, 53/77) emerged as the most predominant RVA strain in 2022. It is noteworthy that G8P[8] was identified for the first time in 2020 and showed a marked epidemic as the second most prevalent RVA strain in 2021 (25.9%, 38/147). On the contrary, the proportion of G9P[8] strains, which were predominant in 2020 and 2021, showed a sharp decrease in 2022 (15.6%, 12/77). The second most common genotype in 2020 was G-P[8] (18.2%, 4/22). In addition, G3P[8], which was identified as the third predominant RVA strain in this study, was mainly detected in 2021 (90.0%, 9/10). (Figure 3C).