“We may never know why this disease is making a comeback.”
Here’s a hint. There is most likely not a federal immunization program in the countries from which your illegal “visitors” originated.
There’s no vaccine against strep, which is what causes scarlet fever.
You dont immunize against scarlet fever. It is strep throat with a rash. There are a lot of diseases immigrants may be bringing in that we have to worry about, but this is not one of them.