i cant speak from experience since i have never had virus toubles of any kind on my pc.
but i think that just as with biological viruses the best defense is education and prevention.
these viruses wouldnt replicate and spread as easily is the general public were well informed about how a virus works, and took preventative measures against this.

this is why HIV has gone down so much in america, people know about it and protect themselves.
this is why HIV spreads out of control in africa where people still dont know how to protect themselves.

it may seem like a strange comparison but thats just what i see.