At first I thought that was silly, the feedback loop from the variation in the virus to this attack having any effect on it's propagation is too slow. But then

At first I thought that was silly, the feedback loop from the variation in the virus to this attack having any effect on it's propagation is too slow. But then I realised in the future we might have virus fighting nanomachines with built-in gene sequencers, and suddenly this becomes much more credible.