It's truly terrifying.  When I grew up, we had the occasional Down's kid, but that was it.  Fast forward 30-40 years later and kids "on the spectrum" is so "normal" that no one bats an eye over it.  Out of about 40 houses surrounding me, I am aware of at least 5-6 kids who are on the spectrum.  This is not normal.  Something(s) caused it.