A targeted disease would only work if the attacker has your genome, so
that should be carefully protected.
> Nanodefenses are good at nanoweapons, but not against
> macroweapons. And vice versa.
>
> Quite probably the first. We are not that far from universal nuclear
> proliferation (not entirely likely, but some bombs may already be
> adrift), and it is very hard to defend yourself against a blast unless
> you know it is coming. The kill radius is so much larger than the
> detection radius if the bomb is hidden (say in a van).
I can imagine some nanodefenses that would be effective against
macroweapons. How about an exoskeleton made of cooperating nanomachines?
It would block attacks when possible and move you out of harm's way when
not. Such armor can reduce the kill radius of a nuclear bomb by protecting
the occupant against thermal radiation and blast effects, and repairing
damages from ionizing radiation.
Nanotechnology can also help detect nuclear weapons by making sensors
cheaper. Eventually every city will probably have a nuclear detector on
every street corner.