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Assessment of Pediatric Admissions for Kawasaki Disease or Infectious Disease During the COVID-19 State of Emergency in Japan

Educational Objective
To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  Is Kawasaki disease (KD) associated with droplet- or contact-transmitted infection?

Findings  In this cross-sectional study of 17 235 pediatric patients, the number of admissions for KD showed no significant change (27.4% decrease) during quarantine owing to the COVID-19 pandemic, whereas there were significant decreases in numbers of hospital admissions for droplet-transmitted or contact-transmitted respiratory tract infections (75.3% decrease) and gastrointestinal infections (86.3% decrease). Thus, the ratio of KD admissions to admissions for these infections increased.

Meaning  These findings suggest that contact or droplet transmission is not a major route for KD development and that KD may be associated with airborne disease.


Importance  The development of Kawasaki disease (KD) has been suggested to be associated with droplet- or contact-transmitted infection; however, its triggers and transmission modes remain to be determined. Under an epidemic of SARS-CoV-2, the COVID-19 state of emergency in Japan served as a nationwide social experiment to investigate the impact of quarantine or isolation on the incidence of KD.

Objective  To assess the role of droplet or contact transmission in the etiopathogenesis of KD.

Design, Setting, and Participants  This multicenter, longitudinal, cross-sectional study was conducted from 2015 to 2020 at Fukuoka Children’s Hospital and 5 adjacent general hospitals. The number of admissions for KD and infectious diseases were analyzed. Participants were pediatric patients admitted to the participating hospitals for KD or infectious diseases.

Exposures  Quarantine and isolation owing to the COVID-19 state of emergency.

Main Outcomes and Measures  The primary end points were the ratios of patients with KD to patients with respiratory tract or gastrointestinal infections admitted from April to May in 2015 to 2019 and 2020. A Poisson regression model was used to analyze them.

Results  The study participants included 1649 patients with KD (median [interquartile range] age, 25 [13-43] months; 901 boys [54.6%]) and 15 586 patients with infectious disease (data on age and sex were not available for these patients). The number of admissions for KD showed no significant change between April and May in 2015 to 2019 vs the same months in 2020 (mean [SD], 24.8 [5.6] vs 18.0 [4.0] admissions per month; 27.4% decrease; adjusted incidence rate ratio [aIRR], 0.73; 95% CI, 0.48-1.10; P = .12). However, the number of admissions for droplet-transmitted or contact-transmitted respiratory tract infections (mean [SD], 157.6 [14.4] vs 39.0 [15.0] admissions per month; 75.3% decrease; aIRR, 0.25; 95% CI, 0.17-0.35; P < .001) and gastrointestinal infections (mean [SD], 43.8 [12.9] vs 6.0 [2.0] admissions per month; 86.3% decrease; aIRR, 0.14; 95% CI, 0.04-0.43; P < .001) showed significant decreases between April and May in 2015 to 2019 vs the same months in 2020 (total, 12 254 infections). Thus, the ratio of KD to droplet- or contact-transmitted respiratory tract and gastrointestinal infections incidence in April and May 2020 was significantly increased (ratio, 0.40 vs 0.12; χ21 = 22.76; P < .001).

Conclusions and Relevance  In this study, the significantly increased incidence of KD compared with respiratory tract and gastrointestinal infections during the COVID-19 state of emergency suggests that contact or droplet transmission is not a major route for KD development and that KD may be associated with airborne infections in most cases.

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Article Information

Accepted for Publication: February 10, 2021.

Published: April 6, 2021. doi:10.1001/jamanetworkopen.2021.4475

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Hara T et al. JAMA Network Open.

Correction: This article was corrected on May 26, 2021, to fix an error in the Discussion.

Corresponding Author: Toshiro Hara, MD, PhD, Kawasaki Disease Center, Fukuoka Children’s Hospital, 5-1-1, Kashiiteriha, Higashi-ku, Fukuoka, 813-0017, Japan (

Author Contributions: Drs Takuya Hara and Toshiro Hara had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Furuno, Yamamura, Toshiro Hara.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Takuya Hara, Furuno, Yamamura, Mizuno, Onoyama, Yashiro, Nakamura, Toshiro Hara.

Critical revision of the manuscript for important intellectual content: Takuya Hara, Furuno, Yamamura, Kishimoto, Murata, Hatae, Takemoto, Ishizaki, Kanno, Sato, Motomura, Sakai, Ohga, Toshiro Hara.

Statistical analysis: Takuya Hara, Furuno, Yamamura, Kishimoto.

Obtained funding: Mizuno, Toshiro Hara.

Administrative, technical, or material support: Furuno, Sato, Toshiro Hara.

Supervision: Furuno, Sakai, Ohga, Toshiro Hara.

Conflict of Interest Disclosures: Dr Sakai reported receiving grants from JSPS Kakenhi and grants from AMED during the conduct of the study. No other disclosures were reported.

Funding/Support: This study was funded by a Fukuoka Children’s Hospital Research Grant.

Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank all the staff in Fukuoka Children’s Hospital Kawasaki Disease Center and 5 hospitals for the patient care. Ami Saitou, BSW (Fukuoka Children’s Hospital), helped collect the data and was not compensated beyond their normal salary. Katie Oakley, PhD, and Alison Sherwin, PhD (both from Edanz Group) edited a draft of this manuscript and were paid a fee.

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