Molecular Epidemiology of Human Astroviruses and Emergence of HAstV4 in Pediatric Patients With Acute Gastroenteritis in Thailand During 2021–2024

Human astroviruses are important causative pathogens of acute gastroenteritis, particularly in young children worldwide. Investigating molecular epidemiology is essential for monitoring the emergence of new strains and understanding the evolutionary dynamics of viruses circulating in pediatric population. In this study, a total of 1680 fecal specimens were collected from children hospitalized with acute gastroenteritis in Chiang Mai, Thailand between 2021 and 2024. Astrovirus infection was screened by using RT-PCR, followed by nucleotide sequencing and phylogenetic analysis to determine genotypes and assess genetic diversity. The overall prevalence of astrovirus infection was 2.0% (34/1680). An increasing trend in astrovirus infection was observed following the COVID-19 pandemic with the annual incidence rates of 0.9% in 2021, 1.4% in 2022, 3.2% in 2023, and 2.2% in 2024. Genotyping revealed the presence of all three major astrovirus clades, classic human astrovirus (HAstV), novel MLB and VA astroviruses, with seven distinct genotypes being identified. HAstV1 and MLB2 were the most predominant genotypes (23.5% each), followed by HAstV4 (20.6%), MLB1 (14.7%), HAstV5 (8.8%), VA2 (5.9%), and HAstV3 (2.9%). Notably, the emergence of HAstV4 was observed in 2024. In conclusion, multiple astrovirus genotypes were detected in pediatric patients with acute gastroenteritis in Chiang Mai, Thailand during 2021-2024. These findings provide important insights into the molecular epidemiology and genetic diversity of human astroviruses in the post-COVID-19 era and highlight the need for continual surveillance to track viral evolution and disease burden.