HIV is present in the blood, breast milk, semen and vaginal fluids of infected people, and can only be passed on to another person if these fluids get into his or her body.

The main ways HIV is transmitted are:

• By anal or vaginal sex without a condom. HIV cannot pass through good-quality condoms, and the failure rate of properly used condoms is extremely low. HIV can also be passed on during oral sex, although this is much less common.
• Through blood-to-blood contact. This mainly happens through sharing drug injecting equipment. In the past, before screening was introduced in the UK, some people were infected by blood and blood products during medical treatment. Very rarely, healthcare workers have been infected through accidents at work, such as needlestick injuries.
• From a mother to her baby. This is also called vertical transmission, and can happen during pregnancy, birth or breastfeeding.

There is more information on HIV transmission on our namlife.org website (written for people with HIV in the UK) - in the sections on Sex and on Mother-to-baby transmission of HIV.