As you said, we don't know who patient 0 is. In fact, there is no patient 0 because measles have never gone away.

If white, middle class antivaxers had gotten the free or low cost vaccines that were mandated when I was a kid, none of this would have happened.

Automatically blaming immigrants is just knee-jerk racism. It also ignores that Hispanics, who come from areas susceptible to tropical diseases, are more interested in vaccinations than pampered Americans who think vaccination is archaic and somehow dangerous.