Not Measels

My son Sam has a virus that isn't measels. He had a fever that came and went, and then he woke up covered with red spots. Unlike my other children he has not had his measels immunization. Abigail also has had a fever and appears to be getting these "measel-like" spots. She is not due to get her immunization until next month. Apparently, this virus that is not measels is contagious, but only to other children who haven't been immunized. My children who have had the measels immunization have not gotten this virus.

I'm also to keep my children with "not measels" home, lest they spread it to other non-immunized children. But it's "not the measels".