HIV can be transmitted through blood, semen, rectal fluids, vaginal fluids, and breast milk of a person living with HIV who has a detectable viral load (measurement of the virus in the bloodstream).
For transmission to occur, the HIV in these fluids must get into the bloodstream of an HIV-negative person. This can happen through a mucous membrane (inner lining of body cavities), open cuts or sores, or by direct injection, such as sharing needles, syringes, or other drug injection equipment.
Transmission can also occur when a pregnant person living with HIV passes HIV to their unborn child. This is defined as perinatal transmission.