You are exactly right with the point about migration. Same goes for us taking international travel too, you expose yourself to greater risks because the stats are different in different countries. If memory serves me correctly (and it is 20 yrs ago now) the rubella outbreak in melbourne in the 80s was traced back to an immigrnat family. So, unless you have the same standards and expectations worldwide, it is never going to be totally eradicated. And I'm not suggesting we should stop immigration either.