HIV transmission can occur when blood, semen (including pre-seminal fluid or “pre-cum”), vaginal fluid, or breast milk from an infected person enters the body of an uninfected person. HIV can enter the body through the anus or rectum, the vagina, the penis, the mouth, other mucous membranes (e.g., eyes or inside of the nose), cuts and sores or through a vein (e.g., injection drug use). Intact, healthy skin is an excellent barrier against HIV and other viruses and bacteria. These are the most common ways that HIV is transmitted from one person to another.

Other common ways HIV can be transmitted include:

  • Having sexual intercourse (anal, vaginal, or oral sex) with a person who has HIV and has not been treated for it.
  • Sharing needles or injection equipment with an injection drug user who has untreated HIV.
  • Untreated women living with HIV can transmit the virus to their babies before or during birth, or through breast-feeding after birth.
  • HIV also can be transmitted through transfusions of infected blood or blood clotting factors. However, since 1985, all donated blood in the United States has been tested for HIV.

The risk of transmission through transfusion of blood or blood products is extremely low. The U.S. blood supply is considered to be among the safest in the world.

Some health-care workers have contracted HIV after being stuck with needles contaminated by the HIV virus or, less frequently, after blood contact with the worker’s open cut or through splashes into the worker’s eyes or inside their nose. HIV is not easily transmitted. It is NOT spread through the air, through water, by insects, or during ordinary social contact. It has NEVER been transmitted by casual contact