By Dean L. Winslow, MD, FACP, FIDSA, FPIDS

Professor of Medicine, Division of General Medical Disciplines, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine

SYNOPSIS: Mitigation in response to COVID-19 has been associated with decreases in common childhood respiratory infections. The incidence of Kawasaki disease from April to December 2020 was significantly decreased from the same period during the previous eight years.

SOURCE: Shulman S, Geevarghese B, Kim KY, Rowley A. The impact of social distancing for COVID-19 upon diagnosis of Kawasaki disease. J Pediatric Infect Dis Soc 2021; Mar 23. doi: 10.1093/jpids/piab013. [Online ahead of print].

Records from the Center for Kawasaki Disease at Lurie Children’s Hospital and other affiliated Chicago-area pediatric hospitals were accessed for the periods Jan. 1, 2020, until March 31, 2020 (pre-social distancing), and April 1, 2020, until Dec. 31, 2020. Data from the same periods in the years 2012 through 2019 were accessed as well. 

The number of cases of Kawasaki disease (KD) diagnosed in the January to March pre-social distancing period of 2020 was 13 (95% confidence interval [CI] from 2012 to 2019: 13.0, 21.7), which is comparable to the corresponding period in 2012-2019. In contrast, the number of KD cases diagnosed from April to December 2020, the coronavirus mitigation period, was 15 cases, significantly lower than the number of cases diagnosed annually from April to December in 2012 to 2019 (2012 to 2019 mean = 46.6; 95% CI: 41.5, 51.7; P = 0.01). To take into account the slight decrease in KD cases from January to March 2020 compared with previous years, the authors calculated the ratio of incidence from April to December cases divided by January to March cases. Again, there was a substantial decrease in April to December cases in 2020, with the incidence ratio of 1.15 (95% CI from 2012 to 2019 ratios is 1.86, 4.15; P = 0.008).

COMMENTARY  

It has long been theorized that KD may be an abnormal immune response to a variety of common childhood respiratory viral infections, perhaps preferentially affecting children who may have polygenic disposition. The finding of decreased KD incidence seen in this study is parallel to the findings of Hatoun et al for common respiratory and enteric viral and some bacterial infection diagnoses during the months of mitigation.1 Thus, this finding supports the hypothesis that KD is triggered by a common childhood infectious respiratory agent.2,3

Shulman et al also looked at the possibility that the decreased number of KD cases during the April to December 2020 mitigation period was the result of parents not bringing their ill children to clinics for care. To address this, the authors examined the number of patient emergency department visits and admissions for acute pyelonephritis from 2016 to 2020. They found no decrease corresponding to the mitigation period.

Hatoun et al reported that COVID-19-related childhood mitigation social distancing measures, including the closure of schools, a stay-at-home advisory, and the use of masks, coincided with a marked reduction in diagnoses of many common infectious diseases in children.1 The most pronounced declines were observed in infections transmitted by the respiratory route, with influenza, croup, and bronchiolitis essentially disappearing during the social distancing period.1

Shulman et al found that the number of cases of KD in early 2020 (January to March) was comparable to the number in the same months during the eight previous years, but that the number of KD diagnoses during the 2020 social distancing era (April to December) was very significantly lower than in the comparable period of 2012 to 2019 less than one-third of the number previously observed (P = 0.008). This finding supports the hypothesis that the agent(s) of KD are transmitted via the respiratory route and that transmission of the agent(s) also is reduced by coronavirus mitigation practices.

Since last year, my colleagues have cared for a small number of children with COVID-19-related multisystem inflammatory syndrome in children (MIS-C) at Lucille Packard Children’s Hospital, and our Medicine service has cared for several adults at Stanford Hospital with MIS-A. The parallels to KD are striking. However, similar to the experience of Hatoun et al,1 while we have been incredibly busy caring for COVID-19 adult patients on our wards and in our intensive care units, the reduction in hospital admissions for severe influenza and other viral respiratory infections has been dramatic. 

REFERENCES

  1. Hatoun J, Correa ET, Donahue SMA, et al. Social distancing for COVID-19 and diagnoses of other infectious diseases in children. Pediatrics 2020;146:e202006460.
  2. Rowley AH, Baker SC, Arrollo D, et al. A protein epitope targeted by the antibody response to Kawasaki disease. J Infect Dis 2020;222:158-168.
  3. Rowley AH, Shulman ST. The epidemiology and pathogenesis of Kawasaki disease. Front Pediatr 2018;6:374.