It happened three times in the last century -- and nearly happened again in 1997. Now experts say that another killer flu epidemic is brewing. Will it emerge to kill millions -- as did the 1918 Spanish flu? Or will it be nipped in the bud, as in the 1997 emergence of chicken flu in humans? There are no easy answers. But now the same experts who led the successful effort to stop the 1997 virus in Hong Kong raise troubling new questions. Those questions come from a report in the June 25 issue of the prestigious Proceedings of the...