Molecular epidemiology of human sapovirus based on the surveillance of wastewater and patients with acute gastroenteritis in Osaka, Japan

Wastewater-based epidemiology has recently emerged as a promising tool for determining the prevalence of infectious diseases in a community. In the present study, human sapoviruses (HuSaVs) detected in wastewater collected weekly from January 2023 to March 2024 were analyzed using qPCR and next-generation sequencing (NGS), and the results were compared with those from clinical surveillance samples obtained from patients with acute gastroenteritis (AGE) in Osaka Prefecture, Japan. The detection trend of HuSaV in wastewater agreed with the clinical surveillance data in that HuSaV genomes increased in the cold season. In wastewater surveillance, five genotypes were detected, including GI.1, GI.2, GII.3, GII.5, and GV.1. GI.2 was not detected in the clinical surveillance. In the phylogenetic analysis, VP1 gene sequences obtained from wastewater were positioned in close proximity to those obtained from clinical samples. It is suggested that the results of wastewater surveillance reflect the status of ongoing HuSaV infection in a community. Interestingly, GV.1 was detected less frequently than GI.1 in clinical surveillance samples, but was predominantly detected in wastewater at nearly all time points, accounting for up to 94.5 % of all reads in November 2023. In particular, in November 2023, most gastroenteritis outbreaks and pediatric AGE cases were attributable to GI.1, but GV.1 was present at a higher proportion in the wastewater surveillance than GI.1. Wastewater surveillance was shown to complement clinical surveillance in that the former might be able to cover asymptomatic carriers. Our results demonstrate the importance of systematic clinical and wastewater surveillance in epidemiological analyses of HuSaV.