Avian A/H5N1 influenza viruses pose a pandemic threat. As few as five amino acid substitutions, or four with reassortment, might be sufficient for mammal-to-mammal transmission through respiratory droplets. From surveillance data, we found that two of these substitutions are common in A/H5N1 viruses, and thus, some viruses might require only three additional substitutions to become transmissible via respiratory droplets between mammals. We used a mathematical model of within-host virus evolution to study factors that could increase and decrease the probability of the remaining substitutions evolving after the virus has infected a mammalian host. These factors, combined with the presence of some of these substitutions in circulating strains, make a virus evolving in nature a potentially serious threat. These results highlight critical areas in which more data are needed for assessing, and potentially averting, this threat.

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doi.org/10.1126/science.1222526, hdl.handle.net/1765/39084
Erasmus MC: University Medical Center Rotterdam

Russell, C.A, Fonville, J.M, Brown, A.E.X, Burke, D.F, Smith, D.L, James, S.L, … Fouchier, R.A.M. (2012). The potential for respiratory droplet-transmissible A/H5N1 influenza virus to evolve in a mammalian host. Science (Vol. 336, pp. 1541–1547). doi:10.1126/science.1222526