A firbolg goes to the RnD agent, looking ill, and says "I really don't feel well, i am tired all the time, i dont know what to do." So the RnD agent says "Well, let me take a bit of your hull and i will send it off for tests"
Next week the firbolg returns, still complaining of the same symptoms, and the agent has some bad news: "There is no easy way to say this... but you are HIV positive."
The firbolg is shocked. "HIV!! I am a fighter! Not a lover! How can that possibly be?"
The RnD agent solemnly replies "I am sorry... but one of your parents must have been a carrier."