Respiratory pathogen trends in patients with Kawasaki disease during the COVID-19 pandemic and respiratory syncytial virus epidemic in Japan

BACKGROUND: Although the etiology of Kawasaki disease (KD) remains unknown, the most common view is that an infectious agent triggers the activation of the inflammatory cascade in predisposed children. The coronavirus disease 2019 (COVID-19) pandemic has led to the establishment of infection control measures, which reduced the overall incidence of respiratory infections; however, a resurgence of respiratory syncytial virus (RSV) infection occurred in the summer of 2021. This study aimed to examine the relationship between respiratory pathogens and KD during the COVID-19 pandemic and the RSV epidemic in Japan between 2020 and 2021. METHODS: We retrospectively reviewed the medical charts of pediatric patients with KD or respiratory tract infection (RTI) admitted to National Hospital Organization Okayama Medical Center between December 1, 2020, and August 31, 2021. All patients with KD and RTI underwent multiplex polymerase chain reaction testing upon admission. We classified patients with KD into the three subgroups—pathogen-negative, single pathogen-positive, and multi-pathogen-positive—and compared their laboratory data and clinical features. RESULTS: This study enrolled 48 patients with KD and 269 with RTI. Rhinovirus and enterovirus were the most prevalent pathogens in both patients with KD and RTI (13 [27.1%] and 132 patients [49.1%], respectively). The clinical characteristics of the pathogen-negative KD group and the pathogen-positive KD group at diagnosis were similar; however, the pathogen-negative group tended to receive additional treatment, such as multiple courses of intravenous immunoglobulin, intravenous methylprednisolone, infliximab, cyclosporine A, and plasmapheresis, more frequently. The number of patients with KD remained stable when RTI was not prevalent but increased following the surge in RTI with RSV. CONCLUSIONS: An epidemic of respiratory infections led to an increase in the incidence of KD. Patients with respiratory pathogen-negative KD could have greater recalcitrance to intravenous immunoglobulin than those with respiratory pathogen-positive KD.