Will H5N1 jump species and risk another pandemic?
The expert consensus is a probable “yes.” Robert G. Webster at St. Jude Children’s Research Hospital in Memphis, Tennessee says that “There is no question that there will be influenza pandemic someday,” and given the number of H5N1 infections that have already occurred and the rate of death, “it would be prudent to develop robust plans for dealing with such a pandemic now.”
There has already been direct human infection by H5N1 but only between close contacts, with no further chains of transmission. This “suggests that the virus has not adapted to efficient human spread, but this should not be a rationale for complacency,” warns Ungchusak, adding that “The person-to-person transmission of one of the most lethal human pathogens in the modern world should serve as a reminder of the urgent need to prepare for a future influenza pandemic.”
Note: Influenza viruses use their “H” or “hemagglutinin” to attach to host-cell surface sialosaccharides. Avian influenza viruses prefer sialic acid (SA)-α-2, 3-Gal whereas human influenza viruses the SA-α-2, 6-Gal-terminated saccharides. (See van Riel, D, Muster, VJ, deWit, E et al. 2006 for more detail; full reference below.)
UPDATE December 26, 2011: The NSABB has asked the journals Science and Nature to withhold certain technical information from the published articles, and editors have agreed.
Chen L.M., Blixt O., Stevens J., et al. In vitro evolution of H5N1 avian influenza virus towards human-type receptor specificity. (2011). Virology: Nov 4 [Epub ahead of print].
Fouchier R.A.M., Munster V.J., Keawcharoen J., et al. Virology of Avian Influenza in Relation to Wild Birds. (2007). J. Wildlife Dis: 43(3) Supplement: pp. S7-S14.
Harmon K. What Will the Next Influenza Pandemic Look Like? (2011). Scientific American. Accessed December 3, 2011.
Ungchusak K., Auewarakul P., Dowell S.F., et al. Probable Person-to-Person Transmission of Avian Influenza A (H5N1). (2005). New England Journal of Medicine: 352(4): pp. 333-244.
van Riel D., Munster V.J., de Wit E., et al. H5N1 Virus Attachment to Lower Respiratory Tract. (2006). Science: 312: p. 399.
Webster R.G. and Govorkova E.A. H5N1 Influenza – Continuing Evolution and Spread. (2006). New England Journal of Medicine: 355(21): pp. 2174-2177.
World Health Organization. Cumulative number of confirmed human cases for avian influenza A(H5N1) reported to WHO, 2003-2011. Accessed January 6, 2012.
Additional information from discussions with Paul S. Keim, PhD, acting chair of the NSABB and Paul Offit, MD, Chief of Infectious Diseases and Director of the Vaccine Education Center at the Children’s Hospital of Philadelphia (CHOP) in Pennsylvania; both of whom will be keynote speakers at the 10th ASM Biodefense and Emerging Disease Research meeting held in Washington DC on 26-29 February.
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