HIV Transmission

HIV can be transmitted from an infected person in the following ways:

Bodily fluids

Many bodily fluids can transmit HIV. These are:

  • Blood
  • Semen and pre-seminal fluid
  • Vaginal Secretions
  • Breastmilk

HIV cannot be transmitted in:

  • Saliva
  • Urine
  • Tears
  • Sweat
  • Faeces

The virus can be transmitted from one person who is already infected to another through sexual intercourse (vaginal, oral or anal intercourse) or non-sexually (such as through sharing needles).

Different ways of sexually transmitting HIV 

  • Vaginal sex
  • Anal sex
  • Oral sex

If an infected man has unprotected vaginal sex with a woman (which includes not using a condom), he can pass on the virus to her through the lining of the cervix, uterus and womb. If she has any cuts or sores (which do not need to be visible) then the risk of  transmission is higher as it makes it easier for the virus to get into the bloodstream. If an infected woman has unprotected vaginal intercourse with a man, she can transmit the virus to him through either a sore or cut on his penis, his urethra or the inside of his foreskin.

Anal sex is a higher risk than vaginal sex as the membrane (lining) of the anus is thinner and more delicate and so it is more likely to tear. For both vaginal and anal sex, the receptive partner is at a higher risk of contracting any STD (STI) than the giving partner.

Oral sex is low risk for contracting and transmitting HIV. This is because saliva has enzymes which break down the virus, and because the lining of the mouth is tougher than the vagina or anus. There is a theoretical risk of  transmission if sexual fluids come into contact with sores or ulcers in the mouth, or if blood from the mouth comes into contact with any genital sores. 

If you already have an STI, then your risk of getting another one, including HIV is higher.  There is also a higher risk if there is any blood present (such as during a woman's period or due to any cuts).

Non-sexual transmission

HIV can be transmitted in the following ways without sexual intercourse:

  • Sharing needles
  • Mother to child
  • Blood transfusions
  • Accidents involving blood
  • Tattoos or piercings

Sharing needles is a very high risk activity for many blood borne viruses, as needles are an efficient way for one person's blood to enter another person's blood stream.

Mothers can transmit many STIs including HIV to their newborns either during pregnancy, delivery or by breastfeeding. If healthcare professionals know that the mother has HIV, then there are drugs which can reduce the risk of transmission of these STIs significantly if a mother knows her status early enough in the pregnancy.

It is  rare to contract the virus through a blood transfusion provided the blood or blood products have been thoroughly screened for any viruses.  Transfusions in  developed countries are routinely screened. In countries where blood supplies are not routinely screened, blood transfusion poses a high risk for transmission.

Healthcare workers can become infected with the virus through a needle stick, or by coming into any contact with infected blood or body fluids. 

If tattoo equipment has been used on someone with the virus and has not been properly sterilized afterwards, there is a risk of transmission.