A Comparative Study of Severe and Critical Influenza B in Children in the 2021-2022 Winter Season.

Introduction: Influenza B viruses are less common than influenza A viruses in most seasons and cause relatively milder forms of infection that are less studied. We witnessed a dominance of influenza B in Shijiazhuang, China, in the 2021-2022 winter season. In this study, we comparatively investigated the severe and critical influenza B in pediatric patients. Methods: Children who were hospitalized from December 2021 to January 2022 and diagnosed with influenza B were included in this study. Those who tested positive for COVID-19 were excluded. Demographic data, clinical features, underlying medical conditions, laboratory testing results, and treatment outcomes were retrieved and analyzed retrospectively. Disease severity was classified as severe or critical according to Chinese expert consensus on diagnosis and treatment of influenza in children. Results: A significantly greater proportion of patients with critical influenza had extra-pulmonary complications and bacterial coinfections. Children with critical influenza B had substantially higher levels of procalcitonin and lactate dehydrogenase, a markedly higher neutrophil percentage and a significantly lower CD4+ lymphocyte percentage. Conclusion: Our findings suggest that, to effectively manage critical influenza B, therapeutic regimens should consist of organ-specific supportive care, antibiotic application if bacterial coinfection is present, and anti-inflammatory and immune-boosting treatments.