The viruses that caused the 2009 influenza A(H1N1) and the 1918 flu pandemics share elements not seen in seasonal flu viruses, report US scientists at the National Institute of Allergy and Infectious Diseases and the US Centers for Disease Control and Prevention. This finding should provide insights into how H1N1 might evolve and inform future vaccine design (Wei C-J. et al. Sci Transl Med. 2010;2:24ra21).
Experiments in mice revealed that the 1918 and 2009 pandemic flu viruses have certain similarities in a surface protein, hemagglutinin, which is instrumental in infecting cells. However, unlike seasonal viruses, which have sugar glycan molecules attached to hemagglutinin, they lack these sugar molecules. The glycans, which protect the virus from antibody detection, are a key feature adopted as a pandemic virus evolves into a seasonal strain.
Friedrich MJ. Flu Clues. JAMA. 2010;303(17):1686. doi:10.1001/jama.2010.525