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

Abstract

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.

Figure 1.. Ratios of the Numbers of Patients With Kawasaki Disease (KD) to Those of Patients With Either Respiratory Tract or Gastrointestinal Infections or to Those of Patients With Respiratory Tract Infection Across 6 Hospitals in Fukuoka

Figure 2.. Ratios of the Numbers of Patients With Kawasaki Disease (KD) to Those of Patients With Respiratory Syncytial Virus (RSV) or Rotavirus Infection Across 11 Hospitals Nationwide

Panel A shows the ratio of KD to RSV infection, and panel B shows the ratio of KD to rotavirus infection. Numbers of patients with KD across 11 hospitals were derived from the KD Rapid Report System. Numbers of patients with RSV and rotavirus infections per sentinel site were derived from the National Epidemiological Surveillance for Infectious Diseases in Japan. The mean number of patients with RSV or rotavirus is displayed as the total number multiplied by 10 per sentinel site.