[MOMMY1]

I was going to put this request in health but b/c it relates to children, I did not. My sister in laws two boys are 3 & 5 or 6 and do not live in that great of conditions. They have contracted a contagious condition that (from what I am told) covers the two boys in red bumps that looks like measle bumps. It is not either measles or chicken pox and there is not a vaccination for this. They run a low grade fever with this condition. Adults can also catch it-they gave it to their baby sitter who is a grown woman. In adults they itch with the spots but supposedly children don't. The entire thing lasts 3-4 weeks. I am wondering if anyone has any clue as to what this is. I have done some research and was considering Fifth disease per what it sounded like (and I believe it starts with an "f") but Fifth disease does not stay contagious the whole time and supposedly these kids are for the whole several weeks. Any help or links as to possible answers, I would be grateful! Thanks!
One other thing-if you think I still should put this under health please politely tell me. Also, what would be a polite way to tell the sister in law that she and her children are not welcome to my sons first birthday if the children are still sick-she has no discretion and brings her children everywhere no matter if they are sick are not-she even sent her children to schoo with these bumps. I am worried for my son but also for the others coming to the party...but along with that she is family and you don't want to be too rude...any helpful (polite) answers would be appreciated! Thanks!