Emergence of G9P[8] rotaviruses in children with acute gastroenteritis in Thailand, 2015-2016.

Human group A rotavirus is a major contagious virus causing gastroenteritis in children. Molecular epidemiological study of group A rotavirus infections in hospitalized children was performed by multiplex RT-PCR during 2015-2016 in Chiang Rai, Thailand. G- and P-genotypes of positive rotavirus samples were further analyzed by one-step and two-step multiplex RT-PCR methods. Among 270 fecal specimens tested, rotavirus was the most prevalent (33.7%), followed by norovirus GII (4.1%), adenovirus (3%), and astrovirus (1.5%). Infection was common in patients aged 12-23 months (45.1%) and occurred mostly in children under 3 years of age (85.7%). The highest peak was in a hot month, March (64.8%). G9P[8] emerged as the most predominant (79.1%), followed by G3P[8] (13.2%), G1P[8] (3.3%), and mixed G-types (4.4%). Interestingly, Chiang Rai G9 strains were clustered within a distinct lineage VII including G9 recently reported since 2010-2015. G9-VII also contained four to five unique amino acid substitutions in the VP7 proteins compared with those of the G9 candidate vaccine strain RVA/Human-tc/IND/116E/1985/G9P[11] and the prototype RVA/Human-wt/USA/WI61/1983/G9P[8], defining the G9-VII as a novel variant. G3 strains were closely related to the "new G3P[8] reassortant variant" with an equine-like VP7 gene that emerged in several countries. This study contributes to the understanding of the genetic diversity, providing scientific support for future vaccine strategies to reduce the morbidity and mortality.