The Prevention Measures for COVID-19 and Changes in Kawasaki Disease Incidence.

BackgroundKawasaki disease is suspected to be triggered by previous infection. The prevention measures for COVID-19 have reportedly reduced transmission of certain infectious diseases. Under these circumstances, the prevention measures for COVID-19 may reduce the incidence of Kawasaki disease.MethodWe conducted a retrospective study using registration datasets of patients with Kawasaki disease who were diagnosed in all 11 in-patient pediatric facilities in Yamanashi prefecture. The eligible cases were 595 cases that were diagnosed before the COVID-19 pandemic (from January 2015 to February 2020) and 38 cases that were diagnosed during the COVID-19 pandemic (from March to November 2020). Incidence of several infectious disease were evaluated using data from the Infectious Disease Weekly Report conducted by the National Institute of Infectious Diseases.ResultsEpidemics of various infectious diseases generally remained at low levels during the first nine months (March to November 2020) of the COVID-19 pandemic. Moreover, the incidence of COVID-19 was 50-80 times lower than the incidence in European countries and the United States. The total number of 38 cases with Kawasaki disease for the nine months during the COVID-19 pandemic was 46.3% (-3.5 standard deviation (SD)) of the average (82.0 (SD, 12.7)) for the corresponding nine months of the previous five years. None of the 38 cases was determined to be triggered by COVID-19 based on their medical histories and negative results of severe acute respiratory syndrome coronavirus 2 testing at admission.ConclusionThese observations provide a new epidemiological evidence for the notion that Kawasaki disease is triggered by major infectious diseases in children.