Sickness was a crucial adaptive problem in the course of evolution, and one solution, particularly in humans,
is support and care from in-group members. The social interaction between sufferers and (potential) helpers was a recurrent social situation throughout human evolution and its outcome was crucial for survival. Thus, respective selection pressures may have yielded specific behavioral adaptations for both the sufferer and the helper role.
Steinkopf, L. (2017). The Social Situation of Sickness: An Evolutionary Perspective on Therapeutic Encounters. Evolutionary Psychological Science, 3(3), 270-286.