The Mutants

Political and Religious forces had banded together to produce an aerial vaccine before the SISSIES virus had spread too far.

A side effect of the vaccine was a loss of memory that took some weeks or months to return. The vaccinated were sent to re-integration camps until their memories had fully returned. Medical tests were run daily on the incarcerated to make sure there was no latent infection present.

In their haste to "save" the human race, the statistical odds of mutated responses were dismissed, to be dealt with later.