Anal and vaginal sex

Unprotected anal and vaginal sex have the greatest risk of HIV transmission. Oral sex is considered in detail in a section below.

The chances of you passing on HIV during unprotected anal or vaginal sex are greatest if you are the active, or insertive partner during sex. The risk is particularly high if you have a high viral load, an untreated STI, or if you ejaculate inside your partner. Similarly, if an HIV-negative person has an untreated STI their chances of contracting HIV from you during unprotected sex are increased.

If you are receptive, or passive during sex, the risk of passing on HIV is reduced, but is still present, especially if you have a high viral load or an untreated STI.

Unprotected vaginal sex also carries the risk of pregnancy. Emergency contraception is available from clinics and from pharmacies without prescription.

Oral sex

The risk of transmitting HIV by oral sex is much less certain.

The Health Protection Agency, which monitors HIV in the UK, estimates that about 1-3% of all sexual transmission of HIV is due to oral sex.

However the evidence is conflicting, with some doctors and studies suggesting that as many as 8% of HIV infections are due to oral sex, with others putting the figure much lower, even at zero.

The risk from oral sex is much lower than the risk from unprotected anal or vaginal sex. Having a very high viral load, an untreated STI, ejaculating in the mouth of the person sucking and bleeding gums or sores or wounds in the mouth of the person sucking seem to increase the very small risk.

Condoms

Condoms, when used properly, provide excellent protection against getting most STIs and passing on HIV to other people, or being reinfected with another strain of HIV.

In the UK and some other countries it was usual to recommend extra-strong condoms for anal sex, however recent research has found that standard strength condoms are just as safe.

Condoms are usually made of latex. Some people are allergic to latex condoms. If this is the case, then polyurethane condoms are a safe alternative.

A water-based lubricant should be used with condoms, as oil-based ones weaken condoms and can cause tiny tears.

If you are having sex for a long time, then it is safest to change condoms every 30 minutes.

HIV and sexual health clinics provide free condoms, and in some cities free condoms can also be obtained from gay venues. Family planning clinics also provide free condoms.

Condoms should be disposed of as rubbish in a bin and not flushed down the toilet or discarded in the street or in parks or fields.