I have an absolutely terrible memory and could be conflating several plots here, but all I can remember is that there was some sort of virus or disease or something that was wiping out a majority of the population, and there were people that were born with different genetics and somehow able to adapt to survive.
I remember in the end there were like 5-9 people left and they chose what continents they wanted to inhabit and attempt to repopulate the earth. Being that they thought they were the only people left.
Any suggestions would be appreciated