If we knew for certain, the puzzle would be much less difficult to solve, although still a challenge. You see, when I look at my puzzle it looks different than your puzzle. The puzzles are similar in many ways, but my pieces don't seem to fit in exactly the same way yours do. Some of the pieces seem identical while other shapes are very different. Each puzzle seems to fit into a subgroup of a handful of puzzles.
Some puzzles have many pieces while some only seem to have a few.
Certainly some children may have been born with autism, but I believe the underlying reason for acquiring the autism is the same. An infection must occur for the immune system to begin its work. The outcome is still the same. The course of autism is set in motion and our once beautiful, perfect little picture now begins to change into a difficult, and incredibly challenging puzzle. Certainly genes play a role in all that we are as an individual, including our immune system.