What you say could well be the case, but that doesn’t make it a leap of logic to think that it could also just as well be the illegal Hispanic kids. They are ones getting an exemption in many public schools from having vaccination records, not the legal children of lefties, and any lefty parents who are that concerned about their kids’ health aren’t as likely to be the ones sending their kids to public schools to spread disease.
Any source is possible. It could be Latin Americans, it could be our huge numbers of Chinese immigrants (who outnumber Latin Americans), both legal and illegal or it could be Middle Easterners (our second largest number of immigrants, who receive NO screening). But the fact that educated Americans are so opposed to things that would protect their children against common viral infections doesn’t bode well, and if something like Ebola gets here, I don’t think we’re going to do any better than they are doing in Liberia.