BackgroundEpidemiological 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.MethodsA 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.ResultsThroughout 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.ConclusionThis 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.

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We are grateful to Thiebaud et al. [1] for their comments about external validation and comparison of four risk scores in patients with upper gastrointestinal bleeding [2]. Even if the AIMS65 does not seem to have any advantage, it is important to assess all prognostic models in a European healthcare system. Unfortunately, the CANUKA score was not published when we wrote the protocol and collected data. However, this model did not present superior performance compared with Glasgow Blatchford Score (GBS). To answer Thiebaud et al. comments, patient at low-risk (GBS ≤ 1) represented 15% of all patients admitted to the emergency department (ED) for upper gastrointestinal bleeding and 33% of patients discharged at home after the ED. The hospitalization rate of patients at low risk was 32%. Using a clinical score seems useful at all and might help ED to prevent unnecessary hospitalization.

The aim of the study was to investigate the normal heart rate range for each body temperature in patients visiting the emergency department (ED) with no other, apparent, coexisting factors causing tachycardia. Methods:This was an observational study conducted in the ED at a single children's hospital between April 1, 2014, and March 31, 2017. Data on all visits were extracted from the electronic triage system and were excluded if they indicated the presence of factors other than body temperature potentially increasing the heart rate. We created age-dependent heart rate percentile curves for body temperature in 6 age categories: 0 to younger than 3 months, 3 to younger than 12 months, 1 to younger than 2 years, 2 to younger than 5 years, 5 to younger than 10 years, and 10 years or older. The curves were created for the body temperatures of 36.0°C to 38.0°C for the 0 to younger than 3 months age group and for body temperatures of 36.0°C to 40.5°C for the other age groups.Results: Of the 113,242 patients included, 61,321 were analyzed. The percentile curves across all age groups were similar despite differences in the baseline heart rate. Heart rate increase was steepest between 37.0°C and 38.0°C at a rate of approximately 20 beats per minute per degree Celsius for all groups. Compared with previous studies in the outpatient setting, including the ED, heart rate was lower in younger patients and was similar among older patients. Conclusions:We created new, age-dependent heart rate percentile curves for body temperature for use in the ED setting. In outpatients, the effect of coexisting factors affecting heart rate, such as crying, may be higher among younger patients.