An increasing trend of human sapovirus infection in Japan, 2009 to 2019: An emerging public health concern

Abstract

Background: Human sapovirus (SaV) is an important etiologic agent of childhood diarrhea. This study aims to investigate the burden of SaV infection in childhood diarrhea in Japan from 2009–2019, to understand the changes in SaV infection after the introduction of rotavirus (RV) vaccination in Japan in 2011. Methods: Stool samples were collected from children aged ≤ 12 years old with acute gastroenteritis (AGE) who visited outpatient clinics of six prefectures in Japan. The viral RNA was detected by RT-PCR and genogroups and genotypes were determined through sequence-based analysis. Results: Among 5697 stool samples, 318 (5.6%) samples remained SaV-positives showing the highest prevalence in June and 12–24 month aged children. The most predominant genotype was GI.1 (56.8%), followed by GI.2 (19.2%), GII.1 (10.8%), GIV.1 (9.4%), GI.3 (1.7%), GII.2 (1.4%), GII.3 and GII.5 (0.3%). Importantly, an increasing trend (P = 0.016) of SaV infection was observed during this period. In particular, SaV-detection rate was increased significantly (P = 0.033) from 4.3% in pre-rotavirus (RV)-vaccination era to 6.1% in post-RV-vaccination era. We provided evidence that this increase in SaV infection was mainly attributed by coinfections. Conclusions: The upward trend of SaV infection, particularly after the introduction of RV-vaccination, is an emerging concern. Attention should be paid to control this upward trend of SaV infection to ensure maximum benefits of implementation of RV vaccines towards reducing overall childhood diarrhea worldwide.