– Why aren’t there viruses that cause good things to happen to our body?

Question

Wouldn’t benefiting the host of the virus be better for the virus itself instead of destroying its host?

In: 1

Answer 1

There may very well be. We don’t know every virus out there, and we certainly have symbiotic relationships with many bacteria.

Actually, a decent chunk of our DNA is made from ancient viral DNA that got stuck in our genomes, and some of that DNA is actually useful. Your saliva, for example, contains an enzyme called amylase that helps you break down starches, and [it turns out that that enzyme is boosted by ancient viral DNA](https://en.wikipedia.org/wiki/Endogenous_retrovirus#Role_in_genomic_evolution) (probably not “intentionally”).