One of my pet peeves in this world, and it's by no means limited to autism discussions, is the gross misuse of the word epidemic. Contageous diseases can be epidemic, non-contageous things like autism and obesity can't. Journalists love big scary words and phrases like "epidemic" and "perfect storm", and they should be slapped for that kind of sloppy sophomoric language.
I've been under the impression (mistaken or otherwise) that epidemic or pandemic, etc., had only to do with incidence; I have understood that the contagion aspect, per se, is only an aspect of the incidence.