Influenza-Associated Hospitalizations in the United States

Abstract

National estimates of influenza-associated mortality have been important for understanding the epidemiology of influenza over time and for resource planning for influenza epidemics and future influenza pandemics.^1-4 However, mortality incompletely reflects the severity of influenza infections because many severe illnesses do not result in death. In addition, influenza types and subtypes have differential effects on morbidity and mortality. For example, during some seasons, influenza A(H1N1) and B viruses are associated with substantial numbers of hospitalizations and outpatient visits but small increases in mortality.^5-7 Furthermore, influenza-associated hospitalizations contribute an important proportion of the total health burden and economic costs of influenza epidemics and pandemics.^2,8-10