In the chapter, Extended Phenotype, of his book, it says whether or not agents in a body would cooperate as part of the body or exploit as parasites, depends on if the way the agents replicate themselves is through sexual intercourse and would be passed down with sperms and eggs to next generation.
In the case of HIV/AIDS, just thinking, actually it could be passed on by sexual intercourse as well as from mother to child. So, as explained in that chapter, in theory, AIDS should act almost as part of the body, interests/benefits at one with the body it resides in. But in fact it can be lethal if the body does not get proper lifetime treatment.
This case came into my mind when studying issues in HIV/AIDS after having read that book. Anyone has any idea why the conflicts here in the theory?