Evolutionary consequences of G9 rotaviruses circulating in Thailand

Abstract

Infection with group A rotaviruses is the main cause of acute gastroenteritis in infants and young children worldwide. Rotavirus G9 is recognized as the fifth most predominant G genotype that spreads throughout the world. In this study, we describe the changing distribution of rotavirus G9 genotype in Chiang Mai, Thailand, from 1989 to 2005. Molecular genetic evolutionary analysis of the G9 rotavirus VP7 gene was performed. The G9 rotavirus in Thailand was first detected in Chiang Mai in 1989 with a low prevalence of 1.98%, but in 2000 and 2001 it had become the most predominant genotype, reaching prevalence of 75% and 92.2%, respectively. Then, the prevalence of G9 reached a peak of 100% in 2002 and decreased abruptly over the next 3 years, i.e. 16.7% in 2003, 32.1% in 2004, and 4.7% in 2005. Our phylogenetic analysis demonstrates that all the G9 rotaviruses circulating in Thailand belonged to lineage III, and clustered closely together based on the year of virus isolation. One amino acid change from Thr to Ile was observed in antigenic region C at position 208 between the G9 strains isolated in 1989 and the strains of 1997–2005. These findings provide the overall picture and genomic data of G9 rotaviruses circulating in Chiang Mai, Thailand.