Epidemiological and Clinical Features of Kawasaki Disease During the COVID-19 Pandemic in the United States

Abstract

Importance: Public health measures implemented during the COVID-19 pandemic had widespread effects on population behaviors, transmission of infectious diseases, and exposures to environmental pollutants. This provided an opportunity to study how these factors potentially influenced the incidence of Kawasaki disease (KD), a self-limited pediatric vasculitis of unknown etiology.

Objectives: To examine the change in KD incidence across the United States and evaluate whether public health measures affected the prevalence of KD.

Design, setting, and participants: This multicenter cohort study included consecutive, unselected patients with KD who were diagnosed between January 1, 2018, and December 31, 2020 (multicenter cohort with 28 pediatric centers), and a detailed analysis of patients with KD who were diagnosed between January 1, 2002, and November 15, 2021 (Rady Children's Hospital San Diego [RCHSD]).

Main outcomes and measures: For the multicenter cohort, the date of fever onset for each patient with KD was collected. For RCHSD, detailed demographic and clinical data as well as publicly available, anonymized mobile phone data and median household income by census block group were collected. The study hypothesis was that public health measures undertaken during the pandemic would reduce exposure to the airborne trigger(s) of KD and that communities with high shelter-in-place compliance would experience the greatest decrease in KD incidence.

Results: A total of 2461 KD cases were included in the multicenter study (2018: 894; 2019: 905; 2020: 646), and 1461 cases (median [IQR] age, 2.8 years [1.4-4.9 years]; 900 [61.6%] males; 220 [15.1%] Asian, 512 [35.0%] Hispanic, and 338 [23.1%] White children) from RCHSD between 2002 and 2021 were also included. The 28.2% decline in KD cases nationally during 2020 (646 cases) compared with 2018 (894 cases) and 2019 (905 cases) was uneven across the United States. For RCHSD, there was a disproportionate decline in KD cases in 2020 to 2021 compared with the mean (SD) number of cases in earlier years for children aged 1 to 5 years (22 vs 44.9 [9.9]; P = .02), male children (21 vs 47.6 [10.0]; P = .01), and Asian children (4 vs 11.8 [4.4]; P = .046). Mobility data did not suggest that shelter-in-place measures were associated with the number of KD cases. Clinical features including strawberry tongue, enlarged cervical lymph node, and subacute periungual desquamation were decreased during 2020 compared with the baseline period (strawberry tongue: 39% vs 63%; P = .04; enlarged lymph node: 21% vs 32%; P = .09; periungual desquamation: 47% vs 58%; P = .16). School closures, masking mandates, decreased ambient pollution, and decreased circulation of respiratory viruses all overlapped to different extents with the period of decreased KD cases. KD in San Diego rebounded in the spring of 2021, coincident with lifting of mask mandates.

Conclusions and relevance: In this study of epidemiological and clinical features of KD during the COVID-19 pandemic in the United States, KD cases fell and remained low during the period of masking and school closure. Mobility data indicated that differential intensity of sheltering in place was not associated with KD incidence. These findings suggest that social behavior is associated with exposure to the agent(s) that trigger KD and are consistent with a respiratory portal of entry for the agent(s).

Figure 1.. Kawasaki Disease (KD) Incidence Before and During the COVID-19 Pandemic

A, Total KD patients for Kawasaki Disease Comparative Effectiveness Trial (KIDCARE) sites: 2018, 894 cases; 2019, 905 cases; 2020, 646 cases. There was a 27.7%-28.6% reduction in case numbers in 2020 compared with previous years. B, Incidence of KD by month of year at Rady Children’s Hospital San Diego during 2002 to 2019. Light blue line is the mean for 2002 to 2019, with errors bars indicating 2 SDs. Cases rebounded to close to within historic levels in late 2021.

Figure 2.. Demographic and Clinical Features of Patients with Kawasaki Disease in San Diego for 2002 to 2019 Compared With 2020 and 2021

A-D, Error bars show the 5th to 95th percentile confidence interval for annual patient counts from 2002 to 2019. B-D, The largest reductions in cases in 2020 were in male children younger than 5 years and among Asian children. In 2021, cases among female and White children also decreased. E-G, Black dots show annual values for 2002 to 2019, with boxes indicating the IQR, the bar indicating the median, and whiskers indicating 1.5 × IQR, for those values. Several clinical features of KD were lower than average in 2020 compared with annual rates in previous years, and strawberry tongue and periungual desquamation remained low through 2021. ^aP < .05. ^bP < .01. ^cP < .10.

Figure 3.. Mobility and Pollution Data

A, Patterns of mobility for Southern California were defined as the fraction of the day spent away from home and Kawasaki disease (KD) incidence, 2019 to 2021. Red and blue curves and shading show the median and IQR for the fraction of the day spent away from home for each day in census block groups that had (red) or did not have (blue) KD cases during that year. Tan lines show dates of onset of fever for each KD case at Rady Children’s Hospital San Diego. Black dashed lines show the 2020 pandemic-related shutdown and are included in 2019 and 2021 for comparison. B and C, Changes in tropospheric no₂ levels relative to the same period in 2019 for CBGs that had or did not have KD cases during that year and pandemic time period. Boxes indicate the IQR; bar, median; and whiskers, 1.5 × IQR. In 2020, during the shutdown period (March 3 to May 31), CBGs with KD cases had significantly smaller reductions in pollution (ie, neighborhoods where the no₂ levels were more similar to prepandemic levels were more likely to have KD cases during that period).

Figure 4.. Monthly Incidence of Kawasaki Disease (KD) and Other Viruses

Respiratory viruses were detected by polymerase chain reaction in children tested at Rady Children’s Hospital San Diego from July 1, 2018, through November 30, 2021. The initial shelter-in-place period for San Diego County is shown in gray.