Additionally, the rapid onset of negative health outcomes was because individuals had been HIV positive for much longer than a clinical definition for HIV positivity was developed. Treatment has improved, but for the early days of the AIDS epidemic there were people who had HIV for years before there was an official diagnosis, so the rate of time from diagnosis to death/disabling symptoms appeared shorter. Now HIV testing is part of established STI screenings, so there's (on average) less time for the virus to inhabit a person before diagnosis.