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, donated blood has been screened for HIV since 1985 in the UK. 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 viral load 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.
