Changing Patterns of Infectious Diseases Among Hospitalized Children in Hokkaido, Japan, in the Post-COVID-19 Era, July 2019 to June 2022

Abstract

Background: Many reports have reported a reduction in respiratory infectious diseases and infectious gastroenteritis immediately after the coronavirus disease 2019 (COVID-19) pandemic, but data continuing into 2022 are very limited. We sought to understand the current situation of various infectious diseases among children in Japan as of July 2022 to improve public health in the post-COVID-19 era. Methods: We collected data on children hospitalized with infectious diseases in 18 hospitals in Japan from July 2019 to June 2022. Results: In total, 3417 patients were hospitalized during the study period. Respiratory syncytial virus decreased drastically after COVID-19 spread in early 2020, and few patients were hospitalized for it from April 2020 to March 2021. However, an unexpected out-of-season re-emergence of respiratory syncytial virus was observed in August 2021 (50 patients per week), particularly prominent among older children 3–6 years old. A large epidemic of delayed norovirus gastroenteritis was observed in April 2021, suggesting that the nonpharmaceutical interventions for COVID-19 are less effective against norovirus. However, influenza, human metapneumovirus, Mycoplasma pneumoniae, and rotavirus gastroenteritis were rarely seen for more than 2 years. Conclusions: The incidence patterns of various infectious diseases in Japan have changed markedly since the beginning of the COVID-19 pandemic to the present. The epidemic pattern in the post-COVID-19 era is unpredictable and will require continued careful surveillance.

Resurgence of human metapneumovirus infection and influenza after three seasons of inactivity in the post‐COVID‐19 era in Hokkaido, Japan, 2022–2023

“…This study demonstrated that hMPV and influenza infections, which had occurred only minimally among patients in Hokkaido Prefecture over nearly 3 years, experienced bouts of re‐emergence during the periods of October to November 2022 and January to March 2023, respectively. In our prior publication, we highlighted a significant resurgence of RSV infection in August 2021 25 . Subsequently, this study revealed that RSV cases remained relatively subdued in 2022 but experienced a significant surge from February to June 2023.…”

“…In our prior publication, we highlighted a significant resurgence of RSV infection in August 2021. 25 Subsequently, this study revealed that RSV cases remained relatively subdued in 2022 but experienced a significant surge from February to June 2023. were also reported in Israel and Australia in 2021. 35,36 Stein et al…”

“…6 During the subsequent 28-month period from March 2020 to June 2022, there were only two patients with influenza A and six patients with influenza B. 25…”

“…However, since 2021, there have been reports of a resurgence of various infectious diseases worldwide 16–24 . In a previous study, we reported the resurgence of respiratory syncytial virus (RSV) infections in Hokkaido Prefecture in August 2021 based on our surveillance of hospitalized children with various infectious diseases from July 2019 to June 2022 25 . Before the COVID‐19 pandemic, RSV infections had been observed in all seasons since 2017 in Hokkaido Prefecture, but the significant outbreak in August 2020 was unexpected 26 .…”

“…[16][17][18][19][20][21][22][23][24] In a previous study, we reported the resurgence of respiratory syncytial virus (RSV) infections in Hokkaido Prefecture in August 2021 based on our surveillance of hospitalized children with various infectious diseases from July 2019 to June 2022. 25 Before the COVID-19 pandemic, RSV infections had been observed in all seasons since 2017 in Hokkaido Prefecture, but the significant outbreak in August 2020 was unexpected. 26 During the same period, respiratory infectious diseases, such as human metapneumovirus (hMPV) infections and influenza, were rarely observed.…”