Why is the advantage to bacteria/viruses that kill a host?

Question

Would it not be more advantageous to be relatively benign and keep on spreading itself around rather than kill the host?

Edit: I meant, “what is the advantage” not why.

In: Biology

Answer 1

>Would it not be more advantageous to be relatively benign and keep on spreading itself around rather than kill the host?

Yes. The vast majority of viruses/bacteria don’t kill the hose for this very reason. It is mostly the ones that jump from one species to the other that become deadly.

As an analogy: Cats prey on birds. Birds that evolved along side cats have evolved ways to evade them like putting their nests in high branches where the cats are too heavy to reach or being hyper alert for ambushes. So the cats may catch enough to survive, but never really end up eating them all. When cats are brought to an island were all the birds nest on the ground and have evolved no fear of cats, the cats will thrive for a while until they eat all the birds and then die off themselves. They didn’t evolve side by side, so they haven’t reached a balance.

That isn’t to say it is impossible for a virus/bacteria to reach some sort of balanced life cycle where the host dies. What’s most important is that the virus/bacteria reproduces, not necessarily that it lives as long as possible in it’s host. A rabid animal’s hyper aggression may get it killed sooner than usual, but if it passes on rabies using that aggression, that’s still a win for the rabies virus.