Influenza B

Influenza B viruses exhibit genetic diversity driven by antigenic drift, a gradual accumulation of mutations in the viral surface proteins HA and NA. Unlike influenza A, influenza B viruses do not undergo genetic reassortment with other influenza B viruses or animal influenza viruses. Antigenic drift in influenza B contributes to the need for periodic updates to the influenza vaccine to ensure an effective match with circulating strains. Influenza B infections disproportionately affect pediatric populations, with children experiencing higher rates of illness and hospitalization compared to adults. The unique feature of influenza B is the presence of two distinct lineages (Victoria and Yamagata), which can co-circulate during a flu season. The co-circulation of two lineages adds complexity to vaccine formulation decisions, as both lineages need to be considered for inclusion in the quadrivalent vaccine. In pediatric populations, the impact of influenza B extends beyond the direct health effects, as school closures and increased healthcare utilization often result from outbreaks. Efforts to control influenza B in children involve vaccination strategies, public health campaigns, and surveillance to monitor circulating strains and their potential impact on pediatric health. Understanding the genetic diversity, antigenic characteristics, and age-specific patterns of influenza B infections is essential for tailoring public health interventions. Ongoing research aims to enhance our understanding of influenza B epidemiology, refine vaccine strategies, and improve outcomes, particularly in vulnerable populations such as children, where the burden of influenza B is most pronounced.