It doesn't really matter where it came from (when my kids got it last summer it had to be from a supermarket cart as we really had not been anywhere else!) what matters is preventing it spreading. If everyone has it / has had it, I personally would accept the child into care. If everyone is well then it is simply irresponsible. Unfortunately, it could well have already spread by now. I am flexible about accepting sick kids; I need the parents to keep their jobs in order for me to keep mine and usually by the time something has 'come out' of the incubation period all the kids will have been exposed already.