I have a theory: the children were never children, but really actually dolls. Now, hear me out! It says that the 30% of all worlds children suffer from the disease. Now, what if a portion of humanity was stricken by an infertility plague? And what if to contain the spread of panic, the government came up with a plan to give the infertile couples the above mentioned dolls. Of course, to sell the illusion, the entire populace is subjugated to a treatment of psychoactive/psychedelic reagents that makes people hallucinate and believe that the dolls are actually children.
The thing is, the reagent formula is not perfect and starts to wear off after a while, boom, illusion broken! BUT! That is not all! There are severe side effects! After the formula is reapplied to a couple, it warps the perception to a point where a doll is no longer perceived as a child, but a horrendous monstrous abomination. Boom!
But hey, thats just a theory. A GAME THEORY!