The Big Think has an article on their recently convened Breakthroughs: Autism series that addresses the concern of Autism being an epidemic. Autism started as a very rare diagnosis, and held the stigma of bad parenting over the parents.
Originally used to identify a group of symptoms in schizophrenia, it began to be associated with children who had social or emotional problems. It wasn't until the 1060's that Autism was finally separated from schizophrenia, and let to heavy-handed medications like LSD, or using electric shock therapy or pain and punishment techniques to modify behavior. Because of this stigma, it's been rarely diagnosed, and rarely discussed.
But now one seems to hear about it everywhere, and see more children with Autism. Why? Is it because it's truly becoming more common? Are children getting Autism from water, pollution in the air, watching too much TV when infants? Monosodium Glutamate? Witches? What's the deal?
According to Dr. Christopher Walsh of the Children's Hospital in Boston, Autism is simply "suffering" from increased awareness and a broader definition of the term. Because the medical field now has more specialists in the field, better and more diagnoses are being made. Add to that the inclusion of various subgroups of the Autism Spectrum (from low-functioning Autism to the higher-functioning Aspergers), more children and adults are being diagnosed.
The article is excellent, and I would highly recommend reading it, or watching the discussion. Autism has always been here, it's just been known by different names, or has been hidden within families. But the important thing is to stop blaming vaccinations, pollution, the tooth fairy, pixie dust, or low-hanging power lines without any evidence (beyond surveys) that provide proof.