Is Kawasaki Disease Caused by a Respiratory Virus?

Kawasaki disease is characterized by high fever, rash, cervical lymphadenopathy, conjunctival injection, oral mucous membrane changes and swelling of the extremities followed by skin sloughing. Despite >50 years of study, no bacterial, viral or other infectious agent has been consistently associated with the illness. The lockdown and social distancing for COVID-19 in March 2020 led to a marked decrease in respiratory virus circulation. This provided an "experiment of nature" to determine whether Kawasaki disease would decline in parallel.

Discharge ICD-10 diagnosis codes were obtained from the Vizient Clinical Data Base for Kawasaki disease and respiratory viruses, and analyzed for the age group < 5 years. Weekly respiratory virus positivity data were also obtained from BioFire Diagnostics.

Common enveloped respiratory viruses declined precipitously from April 2020 through March 2021 to levels at or below historical seasonal minimum levels. Kawasaki Disease declined about 40% compared with 2018-2019, which is distinctly different from the pattern seen for the enveloped respiratory viruses. Strong seasonality was seen for Kawasaki disease as far back as 2010, and correlated most closely with respiratory syncytial virus, human metapneumovirus and less so with influenza virus suggesting there is a baseline level of Kawasaki disease activity that is heightened during yearly respiratory virus activity but that remains at a certain level even in the near total absence of respiratory viruses.

The striking decrease in enveloped respiratory viruses after lockdown and social distancing was not paralleled by a comparable decrease in Kawasaki disease incidence, suggesting a different epidemiology.