[null and void]

Native Americans???? They mention NAs and don't say WHY they're included in this group. Odd.

They may not know why. Sweat lodge maybe?

[Tax-chick]

Sweat lodge maybe?

I thought of that, too. It could just be lowered resistance to infection overall, because of poverty, poor nutrition, poor sanitation. TaxRelief posted the title of an article which referenced a "rural" American Indian community.