system
Given the following post, respond as if you're commenting on Reddit:
human
How far back do infectious diseases go in prehistory?

Not as in, prehistoric human history. What I mean is, how far back do diseases like influenza go? Did dinosaurs have something similar to bird flu, for example? Were multicellular creatures always being attacked by diseases?
gpt
Eugene Koonin, one of the leading evolutionary biologists of our time, in his recent book "The logic of chance" clearly depicts that such "infectious parasites" as viruses were abundant as far back as pre-cellular stage. 

Even the cells themselves were not evolved yet, the "pre-cells" -- ensembles of self-replicating macromolecules -- shared their warm pools with viral "selfish replicators" who were actively exploiting their easily accessible biochemical apparatus.

Seems like the cheating is a legit strategy in some cases.

So these infectious diseases seem to be a) older then the life itself, and b), its inevitable condition.