I wonder what happened to Astronauts and such who were in space at the time the apocalypse begun? Are they infected?
Regardless, i don't think anything will work. If the rest of the world is in ruins i don't think anyone would be there to launch nuclear devices, and waiting them out, while it might be possible, has it's own problems(starvation, dissent and/or rebellion amongst a group, quarrels against other survivors, etc.).
It seems the most feasible option is to hope for a cure and if that doesn't happen, well...the walkers will win.