I know you lovely book people like a challenge!
All I can remember is that one of the characters thinks he/she might have rabies, having been bit by a dog and his/her friend/brother/sister cuts (I think) the wound and they try to hide it from boy/girl's parents. It turns out to be a false alarm.
I thought it might be Stephen King, then I thought it might be one of the Little Women series, but googling hasn't helped me, and it's really bugging me!
Anyone?