How HIV is transmitted

You may be concerned about how HIV can be passed from one person to another. This section explains HIV transmission.

Contrary to many people’s thoughts, HIV is not an easy virus to catch or pass on. HIV can only be passed on through certain body fluids, when a route into the body is available. Only certain body fluids contain HIV in high enough quantities to cause transmission. The table below summaries which body fluids can and cannot result in the transmission of HIV:

Fluids which CAN pass on HIV:

  • Blood

  • Semen (cum)

  • Vaginal fluids

  • Anal and vaginal mucus

  • Breast milk

  • Pre-cum (the fluid produced by a man before he ejaculates)

  • Anal mucus

  • Discharge from sexually transmitted infections (e.g. discharge from chlamydia or gonorrhoea)

Fluids which CANNOT pass on HIV:

  • Tears

  • Saliva

  • Sweat

  • Urine (wee)

  • Faeces (poo)

  • Vomit

  • Spit

Even if body fluids which contain HIV are present, transmission cannot take place unless there is a route into the body. Common routes include:

  • Blood to blood contact: For example, the sharing of needles and injecting equipment provides a direct blood to blood route.

  • Mother to baby: A pregnant woman living with HIV can pass HIV on to her child. The transmission can happen when the baby is in the womb, during birth or through breast feeding. All pregnant women in the UK are offered an HIV test, and if you are HIV positive you can reduce the risk of passing on HIV to your baby through taking anti-viral drugs, and avoiding breast feeding. In some cases it may be recommended that you have a caesarean section. In the UK it is very unusual for HIV to be passed from mother to baby.

  • Unprotected sex: Many of the fluids which are involved in the transmission of HIV may be present during sex. Unprotected sex therefore provides a route for HIV transmission. Unprotected anal and vaginal sex is seen as high risk activities, and while there is a significant risk reduction associated with oral sex, it cannot be deemed as risk free. Therefore, oral sex may present a small, but real risk of HIV transmission.

It is important to acknowledge that HIV cannot be transmitted though activities such as shaking hands, hugging, kissing, sharing cutlery, sharing a bath or sharing a towel with someone who is living with HIV. Many people living with HIV are discriminated against because people are not fully aware how HIV is transmitted.