Help finding name of a book!?

I read a book in elementary school/middle school so its probably 4th-8th grade reading level about a girl who lived in a village that seemed like it was in the 1700/1800s. They are grounded to the village by the thought of an animal or something that will harm them, but then a bunch of the kids start getting sick with something like diphtheria or i can't remember and the girl has to travel to find a cure and it turns out they live in the middle of nowhere and it is actually modern times. The parents of the children made a pact to bring them and raise them in a new "world" as to help shield them or something. Yes this is very similar to the M.Night film The Village but is a young adult or children's book. I hope someone can help! Thanks!