Molecular Epidemiology of Sapovirus Infection in Japanese Children With Acute Gastroenteritis Before and After the COVID-19 Pandemic

Sapovirus (SaV) is one of the pathogens associated with sporadic acute gastroenteritis in infants and children, and also with foodborne outbreaks in all age groups. This study investigated the molecular detection and characterization of SaV in Japanese children with acute gastroenteritis from July 2017 to June 2024, and the results were compared with those of the previous study conducted in 2014–2017. The study period of this study encompassed the period before, during, and after the COVID-19 pandemic in Japan. During the COVID-19 pandemic, both the number of collected samples and SaV-positive samples decreased remarkably. Among 931 samples included in this study, the rate of SaV infection was 7.5% (70/931), which was higher than the previous study at 5.0%, especially the rates of infection after the pandemic increased to 9.8% in 2022–2023 and 16.4% in 2023–2024. Regarding the SaV genotype distribution, GI.1 was the most predominant genotype at 37.1% comparable to those of the previous study during 2014–2017, followed by GII.3, GI.2, GII.1, GII.2 and GIV.1, GV.1, and GII.5 genotypes. In 2022–2023, GII.3 instead of GI.1 was the most common genotype; however, GI.1 resumed the most dominant genotype again the following year. The findings suggested that SaV infection in Japanese children was remarkable after the COVID-19 pandemic, and the systematic surveillance should be conducted continuously in Japan.