How is HIV transmitted?

Whether you have HIV or not, it is important to understand how it can be passed on so that you can protect yourself and others.

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How is HIV transmitted?

To pass on the virus, infected body fluids (semen, vaginal fluids, anal mucous, breastmilk, or blood) need to get into someone else’s bloodstream. There are several ways HIV can be passed on.

The main ways in which HIV is passed on are:

  • Unprotected anal or vaginal sex. The risk from oral sex is lower but still exists.
  • By sharing injecting equipment.
  • From a mother to her baby during pregnancy, birth, or breastfeeding.

    • HIV can be passed on by receiving blood transfusions or other blood-related products from an infected person, or donations of semen (artificial insemination), skin grafts and organ transplants. However, in the UK donated blood has been screened for HIV since 1985. Similarly, screening is in place for organ and sperm donation.

    Other factors that affect whether HIV is passed on

    HIV isn’t actually as infectious as many other sexually transmitted infections (STIs). It isn’t automatically passed on every time a positive and a negative person have unprotected sex, for example.

    There are factors that can affect the risk of it being passed on. These include:

  • Viral load. Having a high amount of virus makes it more likely that you will pass on HIV.
  • Having another STI. If either partner has an STI, it is more likely that HIV will be passed on. 
  • The type of exposure. Sharing injecting equipment holds the highest risk of passing on HIV. Some sexual activities have a greater risk of HIV infection than others. (Find out more.)
  • Being on HIV treatment. This reduces your viral load and makes you less infectious.

    • How is HIV not transmitted?

    Some body fluids, such as saliva, sweat and urine, do not have enough HIV in them to infect someone. HIV is not passed on by spitting, sneezing or coughing.

    You cannot pass on HIV by kissing, by hugging, or by shaking hands with somebody – or any other normal social contact.

    Nor can you pass on HIV to someone else by being in the same place as them, by using the same toilet, or by sharing household items such as cups, plates, cutlery, or bed linen.

    In the UK, there are safeguards in place to ensure that blood, organs and sperm donated for use in medical procedures are not HIV-infected.

    Once outside the body, HIV usually can’t survive for very long at all. Coming into contact with blood or semen that has been outside the body doesn’t generally pose a risk for HIV transmission.

    It is possible for HIV to be transmitted by someone accidentally cutting themselves with a blade or needle they have used to treat a person living with HIV. This is called a needlestick injury and the risk of being infected is very low. However, if someone thinks they have been exposed to HIV that way, post-exposure prophylaxis (PEP) may be an option.

    Similarly, the risk of passing on HIV to someone else if you injure yourself is also very low. Wash away any blood with soap and hot water and cover the wound with a sticking plaster or dressing.

    This article was last reviewed on: 07/09/11
    Date due for next review: 07/09/13

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