The Hot Zone Part 4

I feel like the last part of the reading wasn't really necessary to be part of the book. It wasn't relevant at all to the rest of the book. It doesn't talk about what happened in Reston but instead took us 3 years in the future which was really strange to me, to talk about the author's adventures to the possible origin of the virus. I learned how the virus like AIDS was able to spread so fast when the Kinshasa highway was built and that there are two strands of HIV. I learned as 90% of prostitutes have AIDS and 30% of the people in the vicinity of Mt. Elgon have AIDS. I also learned that AIDS is a fast mutator and people infected by it usually die with many strains in them.
My question was why AIDS was the new focus of this section instead focusing more on the Ebola viruses which the whole book was mainly about.