Is HIV only a gay disease?

No. In fact, the vast majority of cases of HIV in the world are of heterosexual people.

HIV is a sexually transmitted disease that can harm both male and female. If a guy has it, and then goes through copulation with a girl, the girl would then be infected with the disease. It also gets transmitted by sharing blood. if you are a doctor, and you take blood from a patient, and you accidentally poke yourself with the needle you just used to take blood, then a chance of the doctor being infected is big.