The most common ways that HIV is transmitted from one person to another

• By having anal, vaginal or oral sex with an HIV-infected person
• By sharing needles or injection equipment with an injection drug user who is infected with HIV or through tattoo needles
• From HIV-infected women to babies before or during birth or through breast-feeding

The virus can also enter the body through cuts, sores, the eyes, inside the nose or through transfusions of blood or blood clotting factors. The blood supply in the United States is considered to be among the safest in the world.

You can reduce your risk of becoming infected by limiting the number of your sexual partners and by always using a male or female condom when having sex. If you inject drugs, the safest course of action is to stop using drugs with the help of a treatment program. If this is not possible, using new syringes and needles every time or cleaning old syringes and needles with dilute bleach solution may reduce your risk of becoming HIV-infected.

For HIV-uninfected persons who are exposed to HIV, there may be a window of opportunity in the first few hours or days after exposure in which highly active drugs such as protease inhibitors may prevent HIV infection. This is called post-exposure prevention or post-exposure prophylaxis.