Severity of Influenza A(H1N1) Illness
Despite a regional decline in influenza A(H1N1)pdm09 virus infections during 2013–14, cases at a Florida hospital were more severe than those during 2009–10. Examined strains had a hemagglutinin polymorphism associated with enhanced binding to lower respiratory tract receptors. Genetic changes in this virus must be monitored to predict the effect of future pandemic viruses.
In 2009, a novel influenza virus, influenza A(H1N1)pdm09, emerged. The resulting pandemic disproportionately affected persons <65 years of age, but illness caused by the virus was similar in severity to that caused by seasonal influenza. As the 2013–14 influenza season progressed, physicians at a Florida hospital noted that patients <65 years of age were affected in numbers similar to those seen in 2009–10, but with increased severity. To investigate these observations, we obtained the number of influenza admissions during the 2013–14 season, characterized pathologic findings in deceased patients, sequenced subtype H1N1 viruses, and assessed receptor-specific characteristics.
Abstract and Introduction
Abstract
Despite a regional decline in influenza A(H1N1)pdm09 virus infections during 2013–14, cases at a Florida hospital were more severe than those during 2009–10. Examined strains had a hemagglutinin polymorphism associated with enhanced binding to lower respiratory tract receptors. Genetic changes in this virus must be monitored to predict the effect of future pandemic viruses.
Introduction
In 2009, a novel influenza virus, influenza A(H1N1)pdm09, emerged. The resulting pandemic disproportionately affected persons <65 years of age, but illness caused by the virus was similar in severity to that caused by seasonal influenza. As the 2013–14 influenza season progressed, physicians at a Florida hospital noted that patients <65 years of age were affected in numbers similar to those seen in 2009–10, but with increased severity. To investigate these observations, we obtained the number of influenza admissions during the 2013–14 season, characterized pathologic findings in deceased patients, sequenced subtype H1N1 viruses, and assessed receptor-specific characteristics.
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