Surveillance of norovirus among children with diarrhea in four major hospitals in Bhutan: Replacement of GII.21 by GII.3 as a dominant genotype.

NoV remains an important cause of diarrhea among Bhutanese children. Genotype GII.3 from a single ancestor strain has spread, replacing the previously circulating GII.21. Current NoV genotypes are similar to the strains circulating worldwide but are primarily related to those in neighboring countries. NoV GII is prevalent during the cold season, while GI is prevalent during the summer. To develop a NoV infection control policy, further studies are needed.