HIV is usually transmitted sexually, although it can also be spread by sharing needles or from mother to child. For HIV transmission to occur as a result of sex between men, the following needs to be the case:
- One of the men must have HIV (the section Is he likely to be HIV-positive? gives more detailed information about this) and have a viral load high enough to transmit the virus
- The sex must involve body fluids (blood, cum or anal mucus) that contain sufficient quantities of HIV
- These body fluids must get into the bloodstream of the negative man (the section How risky is…? has details about the kinds of sex that facilitate HIV transmission)
HIV transmission occurs when an HIV-negative man is exposed to HIV and the virus infects the cells in his blood. He then becomes HIV-positive. The HIV tests that are most frequently used in GUM clinics can detect HIV infection one month after HIV has been transmitted . There is more information about this on our HIV Testing page.
What body fluids cause HIV to spread?
For HIV transmission to occur, HIV-infected body fluids have to pass into the bloodstream of an uninfected person. While HIV can be found in many different body fluids of a person with HIV, only some body fluids contain a sufficient quantity of the virus to enable HIV infection to occur.
These body fluids are:
- discharge from STIs (such as gonorrhoea)
- anal mucus – anal mucus is a naturally occurring fluid that lines the arse. Its main function in the body is to lubricate your shit as it passes. Research indicates that anal mucus is the body fluid with the highest concentration of HIV .
You cannot become infected with HIV through exposure to piss or saliva.
How does HIV enter the bloodstream?
There are two ways for HIV to get into the blood of an uninfected person:
- directly into the bloodstream through damaged skin, injecting equipment or invasive surgical procedures
- or through mucous membranes
What makes HIV transmission more likely?
- The situation that is most likely to result in HIV transmission is when a man with HIV who is not on treatment (whether or not he has been diagnosed) fucks an HIV-negative man without using a condom and cumming inside him.
- This situation is the most likely to mean HIV infection because a positive man fucking a negative man without a condom means that the negative man is exposed to HIV.
- The cum of an HIV-positive man, who is not on effective HIV treatment, is more likely to have a sufficient quantity of HIV in it to infect the negative man.
- The mucous membrane in the negative man’s arse provides one of the most effective and efficient routes for HIV to enter the bloodstream .
More details about the risks of different sexual acts, both for HIV and for other STIs, can be found in the section How risky is…?.