[Changes in rotavirus epidemic strains]

Rotavirus is a major cause of gastroenteritis in infants and is widely prevalent throughout the world regardless of the hygienic environment. However, it is not easy to understand the overall picture of rotavirus epidemic because of the great variety of genotypes and the large inter-seasonal and regional differences in the prevalent strains. Fortunately, the rotavirus vaccines now widely used around the world are highly effective and safe. The number of rotavirus gastroenteritis cases is declining dramatically, especially in high-income countries. In Japan, rotavirus vaccines have been included in the routine vaccination program since October 2020. Additionally, the impact of the SARS-CoV-2 pandemic control measures on the rotavirus epidemic was also very significant. These synergistic effects have resulted in few rotavirus outbreaks in recent years. Nevertheless, rotavirus is unlikely to be completely eradicated, and indeed a small number of sporadic cases continue to be reported. It will continue to be important to maintain high vaccination coverage and to continuously investigate prevalent strains. This review will provide an overview of the rotavirus epidemic situation in Japan and abroad. Annual changes in domestic epidemic strains that have been revealed by steady research to date will also be presented.