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People living with HIV; how to prevent HIV transmission

It is now established in law that it is a crime to give someone HIV. For this reason it is even more important that all sexual partners are informed of your HIV status and consent to sex or alternatively that you take careful steps to protect your partner to prevent them from acquiring HIV.  The THT website has a helpful section on HIV transmission and the law which is regularly updated.

Things to consider


Telling your partner and others about HIV

This is a difficult thing to do particularly if you have just been diagnosed with HIV yourself.  It is worth thinking it through first as there are a lot of things to consider. For example if your partner is female and has children, then the children could also be affected.  We can provide help with all these matters in the clinic.


Basic protection – condoms or femidoms

HIV transmission is very unlikely if condoms or femidoms are used correctly all the time. Click here for How to Use a Condom.

Transmission of HIV can occur if condoms are not put on at the beginning of sex or they break – but transmission of HIV is not automatic and overall is less than 3%.   If you did have unprotected sex or a condom failure then attend the Wolverton or A&E for PEPSE within 72hours.  Click here for more information on PEPSE



Type of sex

The risk of HIV transmission depends on the type of sex you are having:


Anal sex (receptive or passive)

Most risky 


Least risky

Anal sex (insertive or active)
Vaginal sex for a woman
Vaginal sex for a man
Oral sex (receptive)
Oral sex (insertive)

You are more likely to pass on HIV if you have any kind of STI particularly herpes or syphilis –so it is important to have regular sexual health screens.  Women with HIV should avoid sex during their periods.



Super-infection (Re-infection – risk if both partners are HIV positive)

Couples who are both HIV positive often think that there are no risks to having unprotected sex with each other. Unfortunately this is not completely true.  We now know that there are different strains of HIV so unprotected sex with someone else who has HIV means you could be re-infected with a new strain of HIV.  Some strains lead to more rapid immune deterioration and others contain mutations that may make you resistant to the medication you are taking.  For this reason we advise all HIV positive couples to continue to use condoms or femidoms.



Viral load

The higher your viral load the more likely you are to pass on HIV to a sexual partner.  High viral loads are more likely in someone recently infected with HIV (during seroconversion) or in someone with advanced HIV disease not on antiretroviral therapy (HAART).  HAART reduces viral loads in blood to less than 50 copies per ml. But studies have shown that even when the viral load is undetectable in blood it can still be detected in semen and infect a partner.  Levels of HIV in semen are also increased if someone has a sexually transmitted infection. There have been many case reports of HIV infections occurring this way.  So it is important to continue to use a condom even if your viral load is undetectable.



Oral sex

The risk of transmitting HIV through oral sex is much lower than for vaginal or anal sex but it is not zero.  The precise risk is difficult to ascertain but data suggests that 2.6% of HIV infections in the UK may have been acquired this way. Data from USA and Australia attribute up to 8% of HIV infections in gay men to this route.

The risk of passing on HIV through oral sex is increased:

  • If you have been recently infected with HIV (called seroconversion).
  • If either you or your partner have a STI.
  • If the receiving (passive) partner has sores or ulcers in mouth, gum disease or a sore throat.
  • If the inserting (active) partner has sores or ulcers on his penis.
  • If you ejaculate into your partner’s mouth.

We advise couples to use condoms for oral sex (non-lubricated flavoured ones are available) – particularly with casual partners. It is also important to maintain good oral hygiene by visiting a dentist regularly and to avoid flossing your teeth before oral sex.



What to do if you are HIV positive and your partner is HIV negative (or vice versa)

This is called a sero-discordant relationship. It is probably best to discuss this with your clinic doctor or nurse. It is also important to involve your partner in the discussion so you can reach a mutually agreeable solution.  It’s still possible to carry on with an active sex life but it may be a little different from before as you will need to be prepared with condoms/femidoms and be sure you know how to use them correctly.  In the case of an accident you will need to know how to obtain PEPSE promptly. Click here for more information on PEPSE


Having a baby – where one person is positive and the other negative

It is still possible to have children without them being infected with HIV.

HIV positive man/HIV negative woman

The couple can be referred to a specialist fertility unit for sperm washing. This procedure removes all HIV virus from the man’s semen prior to artificial insemination.

In the UK no babies have been infected with HIV using this procedure.

HIV positive woman/HIV negative man

Women can conceive through artificial insemination using their partner’s sperm.  If necessary this can be undertaken in a fertility unit.  Alternatively it is possible to do it yourself at home – please discuss with your doctor.



HIV positive women and pregnancy

With appropriate treatment during pregnancy the risk of a baby being infected with HIV is now less than 1%. Click here for more information on HIV care and pregnancy.


Further Information