5% to 14% of European population lacked of CCR-5, while almost none of Asians and Africans lacks CCR-5. A theory about this phenomenon is the black death/small

5% to 14% of European population lacked of CCR-5, while almost none of Asians and Africans lacks CCR-5. A theory about this phenomenon is the black death/smallpox in middle ages in Europe attacked CCR5. And the survivors from several black deaths/smallpox outbreaks were descendants of CCR5 mutation. So theoretically we know how people can live with CCR5 mutation. Of course, the immune system is complex. So maybe a healthy CCR-5 Delta 32 person needs some other mutations to keep functioning instead of just losing CCR-5.