I'm not sure that I buy that heterozygotes have a bit of an advantage in terms of tuberculosis. The tuberculosis numbers for Ireland and the British Isles in general were extremely large, and as Khan points out, Brazil is such a diverse place that I'm not sure all the confounding factors were taken into account.

Two of the families in my town, both Irish, had children with cystic fibrosis. It's an absolutely horrible way to die and to watch your child dying.

I would disagree that Ireland, for example, which has the highest incidence, isn't to some degree an inbred population.