Yes, from what I read that is true. It should be clarified that just because something has the potential to cause croup, doesn't mean it will do so in all circumstances in all patients. I said it is "a" causative agent not "the" causative agent. From what I was able to gather from the information I read, the presence of measles was associated with some cases of croup. Obviously not everyone who has measles will experience croup, but the possibility is still there for some to develop croup in the right set of circumstances.