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.
Keywords: D225G polymorphism; Florida; H1N1 subtype; acute respiratory distress syndrome; genetic changes; hemagglutinin; influenza; influenza virus; pandemic; respiratory tract disease; sialic acid; viruses.