RESUMO
OBJECTIVE: To compare the number and incidence of Kawasaki disease (KD) patients in years 2 through 4 of the coronavirus disease 2019 pandemic, and determine the impact of 3 years of implementation of infection control measures and their subsequent relaxation on the epidemiology of KD in Japan. STUDY DESIGN: We conducted a population-based, cohort study including consecutive KD patients in Kobe City between 2021 and 2023. We compared the incidence of KD cases, in relation to timing of infection control measures, as well as infectious disease cases based on a regional surveillance system. Data from a previous 2016 through 2020 study were used for comparison. RESULTS: A total of 566 children with KD were identified during the study period. During the infection control period in 2021 to 2022, the incidence of KD remained low compared with the prepandemic level (281.3 and 327.5/100 000 children aged 0-4 years in 2021 to 2022 and 2016 through 2019, respectively), but a recovery trend began in the 0-1-year age group. During the relaxation period in 2023, the incidence of KD increased across a wide-age range, reaching the highest recorded in Japan (426.7/100 000 children aged 0-4 years), and the median age of onset increased to age 30 months. The resurgence of KD coincided with the epidemic patterns for multiple infectious diseases in 2023. The seasonality of KD observed before the pandemic was altered. CONCLUSIONS: KD resurged in 2023 after relaxation of the prolonged coronavirus disease 2019 pandemic restrictions in Japan. This phenomenon coincided with the rise of multiple infectious diseases, and supports the pathogenesis of KD being triggered by infectious agents.
RESUMO
Background: Epidemiological studies in Kawasaki disease (KD) have suggested infectious aetiology. During the COVID-19 pandemic, measures for mitigating SARS-CoV-2 transmission also suppress the circulation of other contagious microorganisms. The primary objective is to compare the number and incidence of KD before and during the COVID-19 pandemic in Japan, and the secondary objective is to investigate temporal association between the KD epidemiology and activities of SARS-CoV-2 and other viral and bacterial infections. Methods: A retrospective cohort study was conducted between 2016 and 2020 in Kobe, Japan. We collected information of hospitalised KD children in Kobe. Child population was identified through the resident registry system. Activity of COVID-19 and 11 other infectious diseases was derived from a public health monitoring system. Monthly change of KD incidence was analysed using a difference-in-difference regression model. Results: Throughout the study period, 1027 KD children were identified. KD had begun to decline in April 2020, coinciding with the beginning of the COVID-19 pandemic. The number of KD cases (n=66) between April and December 2020 was 40% of the average in the same period in 2016-2019 (165/year). Annual KD incidence was 315, 300, 353, 347 and 188/100 000 children aged 0-4 years in 2016-2020, respectively. The difference-in-difference value of KD incidence was significantly reduced in the fourth quarter in 2020 (-15.8, 95% CI -28.0 to -3.5), compared with that in 2016-2019. Sentinel surveillance showed a marked decrease of all infectious diseases except exanthema subitum after the beginning of the COVID-19 pandemic. There were 86 COVID-19 cases aged <10 years and no KD children associated with COVID-19. Conclusion: This study showed that the number and incidence of KD was dramatically reduced during the COVID-19 pandemic in Japan. This change was temporally associated with decreased activities of various infectious diseases other than COVID-19, supporting the hypothesis of infection-triggered pathogenesis in KD.