If you have a Sexually Transmitted Disease (STD) it is easier for you to get HIV. Having an STD changes the cells lining the vagina, penis, rectum or mouth. This makes it easier for HIV to enter your body. If you already have an STD, you are more likely to get infected with HIV if you have sex with someone who has HIV and you do not use a condom.
You are more likely to get HIV if your partner has HIV and an STD. People with both HIV and an STD have more HIV in their semen (cum) or vaginal fluid. This makes it easier for a person with an STD or HIV to give the virus to others when having sex without a condom.