Answer:
I think that first of all it gets the user's brain somewhere else, we must look at the reasons for HIV to come to a human. According to the NHS, in the UK it is mostly because of having sex with a person who has HIV without using a condom. It is transmitted by semen, vaginal fluids, including menstrual blood, breast milk, blood and lining inside the anus. So drug abuse might cause to all of the listed stuff above which will cause to HIV.
