Interesting, microbes like anything will evolve when attacked directly. This is why holistic medicine is a better approach (stengthening the natural forces that eliminate, or making the environment less appealing for them). Antibiotics and the like have similarly forced bacteria and the like to get stronger (i.e. get stronger or die) so what we are left with is all the strong bacteria and viruses.

I remember when a cold last 3 days, now they last weeks and months. They will continue to get stronger the more we directly attack them. A similar thing happend with rabbits when we introduced myxomatosis. All the weak rabbits died and only those who became immune or were stonger survived. Sadly we don't seem to learn very well.

Ultimately a virus or bacteria of super strength with potentially wipe out all the weaker humans. That said, there seems to be little concern of such as we are considered over-populated already. Nature always balances everything, that is its purpose. Everything that evolves into balance will survive, everything else will fall away, so it has been, so it always will be. Adapt or die.