More Evidence Kawasaki Disease Trigger Is Something in the Air

The pandemic set the stage for a drop in Kawasaki disease (KD) cases that later rebounded with the lifting of mask mandates and return of in-person school, a study found.

Supporting the theory that KD can be triggered by airborne particles, researchers found that 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 in 2020.

That was the year the U.S. saw 646 KD cases nationwide, down from 905 in 2019 and 894 in 2018, reported Jane Burns, MD, of the University of California San Diego and Rady Children’s Hospital-San Diego, and colleagues in JAMA Network Open.

Their data support prior observations of reduced KD cases across Chicago, Asia, and Finland during 2020.

“The pandemic has shown that limiting exposures to aerosols and large droplets through some combination of masking, social distancing, and hand hygiene can reduce the incidence of KD in diverse communities throughout the globe,” the study authors concluded.

KD is rare, albeit the most common acquired heart disease in children. The condition causes blood vessels to be inflamed and can lead to heart complications such as heart attacks, congestive heart failure, and sudden death.

Burns’ team found from available data for the year 2021, limited to San Diego alone, that KD cases rebounded in the spring around the time mask mandates were lifted.

Yet cellphone data tracking people’s locations suggested that this region’s stay-at-home orders — another public health measure during COVID-19 — had not been related to the incidence of KD. And KD cases fell less dramatically than some respiratory viruses during the shelter-in-place period.

“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 [socioeconomic status] during the pandemic,” Burns and colleagues wrote. “Sheltering in place may have had less impact on KD … if the triggering agent(s) are indeed airborne particles.”

Such particles may include viruses, pollutants, and microbial aerosols.

Michael Portman, MD, of Seattle Children’s Hospital and the University of Washington School of Medicine, who was not involved with the study, said the literature does not support masking or shelter in place for the sake of reducing KD, and cautioned against a change in clinical practice.

During COVID-19, KD patients may have been diagnosed with multisystem inflammatory syndrome in children (MIS-C) instead due to overlapping symptoms, he told MedPage Today.

The present study relied on KIDCARE patients recruited from 28 participating pediatric centers in the U.S. Participants were 2,461 consecutive children diagnosed with KD in 2018-2020.

The San Diego cohort stood by itself and had more detailed demographic and clinical data going back to 2002. These 1,461 patients (median age 2.8 years, 61.6% of whom were boys) were drawn from Rady Children’s Hospital, which treats nearly all KD patients in the region.

San Diego data showed school-age children, but not infants, having a lower incidence of KD during pandemic shutdowns.

“Possible explanations include the fact that infants would not be subjected to pandemic-era behavior changes, such as masking, and changes in exposure to the KD trigger within the home, so decreased mobility would have little effect on KD incidence in this group,” Burns’ group reasoned.

“The fact that the pandemic affected each age group differently supports the idea that there are multiple triggers of KD, and different children develop the disease after exposure to different ones,” Burns added in a press release.

She and her collaborators acknowledged the small samples in their report and the fact that KD incidence is known to vary widely between years. Another major limitation is the study’s reliance on neighborhood-level, non-individualized mobility, income, and pollution data.

“The observations presented here suggest several productive avenues for research into the etiology of KD,” the investigators maintained.

“The data suggest that oropharyngeal swabs from patients, particularly infants, coupled with in-home or local air sampling followed by metagenomic sequencing may be instructive,” the team said. “Focusing on the home environment for infants may be more productive, as their exposures are potentially more limited.”

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