Common routes include:
Contact with the mucous membranes of genital or anal tissue. A mucous membrane is a type of tissue that is a less effective barrier than skin. The inner foreskin is also a mucous membrane.
Ulcers, sores, tears or micro abrasions (microscopic cuts) on genital tissue (to the vagina, penis or anal lining).
Any direct route into the bloodstream including cuts in your mouth. Sharing needles and injecting equipment has one of the highest risks of transmitting HIV. This is because there is a direct blood-to-blood route.