The Shielder is first of this series, but seems to chronologically take place after the next one the Shadower.
Nessa dan Ranul had severe medical problems as a child which has left her alone and an outcast. The Shielder way of life is harsh and basically they live by survival of the fitest. Nessa’s brother had helped keep her alive and sane since she was cast out of her society when she was only 12.
A virus has been spreading throughout the colony and Nessa decides to volunteer to be a live host for the virus so that she may try to win back the respect of her family.