Equal Prevalence of Genotypes ON1 and BA of Human Orthopneumovirus in Riyadh, Saudi Arabia, in 2022.

Human orthopneumovirus (HOPV) is a major cause of acute respiratory tract infection (ARI) in children around the world. The present study was conceptualized to detect and characterize human orthopneumovirus in 640 NPAs collected from symptomatic ARI pediatric patients younger than 2 years of age. The samples were collected from a hospital in Riyadh, Saudi Arabia, during winter 2022. Orthopneumovirus was detected in 98 (15.31%) of the 640 NPAs. No significant difference in the prevalence of HOPV-A (49%) and HOPV-B (51%) was observed during the study period as they circulated at similar frequencies. The HOPV-A strains (33) and HOPV-B strains (47) clustered into ON1 and BA genotype, respectively. The ON1 genotypes were further categorized into the subgenotype GA-2.3 and three different lineages, GA-2.3.5, GA-2.3.6a, and GA-2.3.6b, whereas the BA genotypes were categorized into the GB-5.0 subgenotype, entirely belonging to the GB-5.0.5a lineage. This is the first report to characterize orthopneumovirus strains from Saudi Arabia using a recently reported method. Several mutations, a few N-/O-glycosylation sites, and some purifying selections were observed in both the ON1 and BA genotypes. The present study demonstrates the equal prevalence of the ON1 and BA genotypes, in contrast to earlier reports on HOPV-A prevalence in the region. Understanding the change in the genotype distribution of HOPV requires the uninterrupted surveillance and genetic characterization of HOPV in circulating respiratory infections. These findings may contribute to a better understanding of HOPV evolution and the dynamics of its distribution at the local and global levels, resulting in improved understanding of epidemics.