From Rolling Stone (link):
Carlos nonchalantly asks whether his drink was made with whole or skim milk. He takes a moment to slurp on his grande Caffe Mocha in a crowded Starbucks, and then he gets back to explaining how much he wants HIV, the virus that causes AIDS. His eyes light up as he says that the actual moment of transmission, the instant he gets HIV, will be “the most erotic thing I can imagine.” He seems like a typical thirty-two-year-old man, but, in fact, he has a secret life. Carlos is chasing the bug…
…Carlos is part of an intricate underground world that has sprouted, driven almost completely by the Internet, in which men who want to be infected with HIV get together with those who are willing to infect them. The men who want the virus are called “bug chasers,” and the men who freely give the virus to them are called “gift givers.” While the rest of the world fights the AIDS epidemic and most people fear HIV infection, this subculture celebrates the virus and eroticizes it. HIV-infected semen is treated like liquid gold.