I'm still reading (and very much enjoying) last Friday's Science
issue on the flu pandemic. In , Anthony Fauci and Francis
Collins summarize very well why the flu presents a potential
threat: "Influenza viruses have animal reservoirs, especially in
birds and pigs. They can undergo extensive genetic changes and
even jump species, sometimes resulting in a virus to which
humans may be highly vulnerable."Over the last hundred years,
this happened four times: in 1918 (the Spanish flu), in 1957
(the Asian flu), in 1968 (Hong Kong flu), and, the last time, in
2009 with the H1N1 pandemic (swine flu). H5N1 has not initiated
a pandemic because it is rarely passed between humans and it
infects only through direct contact with infected birds. So far
there have been about 600 total cases, of which nearly 60% have
resulted in deaths (though this last number is likely to be
inflated as often not all non-fatal cases are reported to
hospitals). Given these statistics, if the virus were to spread
more easily (for example throu