(This is fiction, no deeper truth is aimed at than we are vulnerable to pandemics)
Enemy scientists developed virus strains, then attempted to corrupt human DNA
Using monkeys, then human subjects finally sorting results, successes and rejects
Human society devolved after introduction with no way to aim the vile corruption
Then the species approached extinction, the design was to slay, with no remedy
Eventually only the rare mutant survived no clarity existed, no answer found
As humanity entered bestial civilization phase, to spiral down, into the depths
Never to return