HIV Kills Dogs

Sitting in the back table in biology, they could get away with almost anything. They consisted of four girls, Renee and Demi, Andrea and Lauren. Andrea was quiet and did all the work, Lauren went along with all the puns.
The teacher was droning on about the side affects of AIDS, "The symptoms of HIV, if there appear to be any, are those that appear to be of a cold."
"Sorry guys, I think I have HIV," Renee said in the midst of a coughing fit.
"I can't believe you didn't tell me before last night!"
"Sorry, Lauren," her voice cracked.
"That's the last time I'm letting you sleep with me," yelled Demi, "You really sound like a dying dog by the way."