PANDAS can see that autism can happen at any time, in response to an illness. This research paper goes further linking any immune stressor to physically changing the brain chemistry/biology to improve your chances at living. You actually avoid human contact and wash more often - on a subconscious level. Manifest as ASD and OCD and others.
You have seen the opposite in mice infected with a parasite, who seem more attracted to cats, - https://www.nature.com/news/parasite-makes-mice-lose-fear-of-cats-permanently-1.13777
"The results are novel, as this sensitive and comprehensive testing has revealed how prenatal and early postnatal immune activation may regulate core behavioral signs associated with ASD and certain other developmental disorders through changes in signal flow between different structural components of behavior-driving neural circuits," said Bolshakov. "These findings may be of a significant translational value, as they provide important clues to understanding the mechanisms of these disorders and potentially their treatment."
I'm pretty sure the cause of autism is unknown.
More importantly, as far as 'real' science can tell, it's not 'curable'... any more than being dyslexic or colour-blind is...
Honestly? If we could find out what causes it I think we should be giving it as a 'low dose' to babies to trigger Asperger-level autism - if EVERYONE really was 'a bit autistic' imagine how much easier life would be... plus we'd probably have Mars colonised, global warming fixed, the oceans de-polluted etc. in a couple of decades...
Sure, there'd be a few poor individuals that didn't develop autism and their lives would be miserable but, welcome to OUR world...
I don't know, I kind of like being in the superior 1%.