Pandemic Public Health Measures May Have Eased Kawasaki Disease

Pandemic Public Health Measures May Have Eased Kawasaki Disease

The social behavior associated with the COVID-19 pandemic may have reduced the incidence of Kawasaki disease, according to results of a cohort study of nearly 4,000 children.

The incidence of Kawasaki disease in the United States declined by 28.2% between 2018 and 2020, possibly as a result of factors including school closures, mask mandates, and reduced ambient pollution that might reduce exposure to Kawasaki disease (KD) in the environment, but a potential association has not been explored, wrote Jennifer A. Burney, PhD, of the University of California, San Diego, and colleagues.

KD received greater attention in the public and medical communities because of the emergence of multisystem inflammatory syndrome in children (MIS-C), which is similar to, but distinct from, KD, and because of the noticeable drop in KD cases during the pandemic, the researchers said.

In a multicenter cohort study published in JAMA Network Open , the researchers reviewed data from 2,461 consecutive patients with KD who were diagnosed between Jan. 1, 2018, and Dec. 31, 2020. They conducted a detailed analysis of analysis of 1,461 children with KD who were diagnosed between Jan. 1, 2002, and Nov. 15, 2021, at Rady Children’s Hospital San Diego (RCHSD), using data from before, during, and after the height of the pandemic. The median age of the children in the RCHSD analysis was 2.8 years, 62% were male, and 35% were Hispanic.

Overall, the prevalence of KD declined from 894 in 2018 to 646 in 2020, across the United States, but the decline was uneven, the researchers noted.

In the RCHSD cohort in San Diego, KD cases in children aged 1-5 years decreased significantly from 2020 to 2021 compared to the mean number of cases in previous years (22 vs. 44.9, P = .02). KD cases also decreased significantly among males and Asian children.

Notably, the occurrence of the KD clinical features of strawberry tongue, enlarged cervical lymph node, and subacute periungual desquamation decreased during 2020 compared with the baseline period, although only strawberry tongue reached statistical significance (39% vs. 63%, P = .04). The prevalence of patients with an enlarged lymph node was 21% in 2020 vs. 32% prior to the pandemic (P = .09); the prevalence of periungual desquamation during these periods was 47% vs. 58%, P = .16).

The researchers also used data from Census Block Groups (CBGs) to assess the impact of mobility metrics and environmental exposures on KD during the pandemic for the San Diego patient cohort. They found that KD cases during the pandemic were more likely to occur in neighborhoods of higher socioeconomic status, and that neighborhoods with lower levels of nitrous oxides had fewer KD cases.

Overall, “The reduction in KD case numbers coincided with masking, school closures, reduced circulation of respiratory viruses, and reduced air pollution,” the researchers wrote in their discussion of the findings. “A rebound in KD case numbers to prepandemic levels coincided with the lifting of mask mandates and, subsequently, the return to in-person schooling,” they wrote.

The study findings were limited by several factors including the small sample sizes, which also limit the interpretation of mobility and pollution data, the researchers noted. Other limitations include the high interannual variability of KD and the inclusion of 2021 rebound data from the San Diego region only.

“Although our original hypothesis was that shelter-in-place measures would track with reduced KD cases, this was not borne out by the San Diego region data. Instead, the San Diego case occurrence data suggest that exposures that triggered KD were more likely to occur in the home, with a shift toward households with higher SES during the pandemic,” the researchers noted. However, “The results presented here are consistent with a respiratory portal of entry for the trigger(s) of KD,” they said.

Study Fails to Validate Its Conclusions

“This study attempts to test the hypothesis that various social restrictions were associated with a decrease in rate of diagnosed Kawasaki disease cases during portions of the SARS-CoV-2 pandemic,” Mark Gorelik, MD, assistant professor of pediatrics at Columbia University, New York, said in an interview.

“However, it appears that it fails to achieve this conclusion and I disagree with the findings,” said Gorelik, who was not involved in the study but served as first author on an updated Kawasaki disease treatment guideline published earlier this spring in Arthritis & Rheumatology.

“The study does not find statistically significant associations either with shelter in place orders or with cell phone mobility data, as stated in the conclusion, directly contradicting its own claim,” Gorelik said. “Secondly, the study makes an assumption that various methods, especially the wearing of masks by children and school closures, had a significant effect on the spread of respiratory viruses. There are no prospective, population based, controlled real world studies that validate this claim, and two prospective controlled real-world studies that dispute this,” he emphasized. “Cloth masks and surgical masks, which were the types of masks worn by school students, are also known to have a nonsignificant and paltry – in the latter, certainly less than 50%, and perhaps as little as 10% – effect on the reduction of respiratory viral spread,” he added.

“Mechanistic studies on mask wearing may suggest some mask efficacy, but these studies are as valid as mechanistic studies showing the effect of various antifungal pharmaceuticals on the replication of SARS-CoV-2 virus in culture, meaning only valid as hypothesis generating, and ultimately the latter hypothesis failed to bear out,” Gorelik explained. “We do not know the reason why other respiratory viruses and non-SARS-CoV-2 coronaviruses declined during the pandemic, but we do know that despite this, the SARS-CoV-2 coronavirus itself did not appear to suffer the same fate. Thus, it is very possible that another factor was at work, and we know that during other viral pandemics, typically circulating viruses decline, potentially due to induction of interferon responses in hosts, in a general effect known as ‘viral interference,’ ” he said.

“Overall, we must have robust evidence to support benefits of hypotheses that have demonstrated clear damage to children during this pandemic (such as school closures), and this study fails to live up to that requirement,” Gorelik said. 

The study was supported by the Gordon and Marilyn Macklin Foundation and the Patient-Centered Outcomes Research Institute. Burney and Gorelik had no financial conflicts to disclose.

This story originally appeared on, part of the Medscape Professional Network.

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