Flu viruses can swap genes with each other, so if someone carrying ahumanflu virus catches the new bird flu, the two strains could mingle inside the victim's body, creating a new, highly contagious and lethal human plague.
In this respect if we compare the 1918 Spanish flu, a swine flu variant (largest human killer of all time that took up to 100 million lives) and the 2009 Swine Flu, we see that a drugs cure would come far too late and most of us (between 300milion and over 1 billion worldwide is estimated) would be dead.