Resurgence of Respiratory Syncytial Virus Infection During an Atypical Season in Japan

摘要

To the EDiTOR—Yeoh et al. [1] had reported the effectiveness of public health measures introduced during the coronavirus disease 2019 (COVID-19) pandemic on respiratory syncytial virus (RSV) infections in Western Australian children. Later, they reported the obvious resurgence of RSV cases from last September, and that the epidemic season had shifted by about half a year [2]. In Japan, we recently began to face a similar situation to that of Australia. Here, we present the data from the Japanese pediatric sentinel surveillance system under the National Epidemiological Surveillance of Infectious Diseases Program (Figure 1) [3]; such reports are based on laboratory diagnosis. In Japan, RSV infections typically occur as an epidemic in the autumn season [4]. However, a significant reduction in the seasonal trend of RSV infection was observed in 2020. We thought that strict measures to avoid severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission had also prevented the transmission of other respiratory viruses [5]. However, a resurgence of RSV infections occurred in some parts of western Japan during the spring season and eventually spread to the whole of Japan during early summer. This epidemic trend has not been observed ever since RSV surveillance started in 2012 [3]. From January 13 to March 21, 2021, and from April 25 to June 20, 2021, the Japanese government declared a state of emergency for COVID-19 in major cities. Measures regarding limited phys-