Q and A

Question

if you have sex with someone who has HIV are you guaranteed to catch HIV?

10 January 2018. Related: All topics, HIV transmission.

Answer

Answer: Simon Collins

No, the opposite is true, HIV is a difficult virus to catch.

The actual risk in any single situation probably vary from zero (no risk) to to less than 1 in 20,000 (0.05% risk per exposure) to 1 in 10 (10% risk per exposure). This will depend on many things, including: the viral load of the HIV positive partner, the type of sex, whether you use a condom, if there are STIs, genetics etc).

The risk is zero if the positive partner is on treatment (ART) with an undetectable viral load.  An undetectable viral load makes HIV untransmittable. (See: The evidence for U=U).

Low risks (1 in 5,000) include oral sex generally (not in early infection), or perhaps the risk of a condom breaking.

High risk – perhaps 1 in 100 to 300 – is estimated from vaginal or anal intercourse without using a condom (not accounting for viral load), or for oral sex with someone who has recently been infected.

Highest risk would involve blood to blood contact with someone who has a high viral load.

Although HIV is not an easy virus to catch – it does only takes one exposure for infection to occur in any risk setting other than zero. There is probably zero risk if the positive partner has undetectable viral load, if the negative partner uses PrEP or when condoms are used properly.

Many HIV positive people have sex with HIV negative people, including in long-term relationships, without the negative person catching HIV.
See also the info and links from this page.

This question was updated in January 2018 from an original answer posted in May 2008. i-Base no longer answers individual questions about HIV transmission and risk. (See: Question 1, 5, 6 and 9 at this link).

Comments to this thread are now closed.

61 comments

  1. Simon Collins •

    If your partner is on treatment with undetectable viral load then the risk of HIV transmission is very low.
    http://i-base.info/qa-on-the-partner-study

    If your partner is not on HIV treatment then using a condom or PrEP will stop HIV transmission.

    Answers to questions on transmission and testing are already online at the FAQ page.
    http://i-base.info/qa/factsheets/hiv-transmission-and-testing

    or in this guide:
    http://i-base.info/guides/testing

  2. nelisiwe •

    I had unprotected sex with my partner I want to ask if he is positive are any chances to get hiv if I dnt have SIT or any sound on my private part

  3. Simon Collins •

    Hi Brian

    Answers to questions on transmission and testing are already online at the FAQ page.
    http://i-base.info/qa/factsheets/hiv-transmission-and-testing

    or in this guide:
    http://i-base.info/guides/testing

    The average risk from having anal sex once is still less than 1% so you are more likely to still be negative. Reading info in the links will help understand these risks and make you more informed and confident about HIV.

  4. brian •

    I have anal sex with a partner as the bottom.I was foolish and didn’t make my partner finish using ( it pulled off my partner ) a condom.My partner did ejaculate in me.I don’t know if that person has hiv or not and I’ll probably never see that person again.If they did have hiv ,will I definaltly get hiv? I truly don’t believe I bled but do not know.I did not observe and blood later in the shower or on the toilet.please let me know.

  5. Simon Collins •

    Hi Sam, answers to questions on risk and testing are online at the FAQ page.
    http://i-base.info/qa/factsheets/hiv-transmission-and-testing

  6. Sam •

    Accidentally , got off condom and I had intercrouse with her almost 4 to 6 mint without Condom . I Donot know her status but is it any chances to get infected if she I shiv positive

  7. Simon Collins •

    Hi Kemaerse, if you use condoms then you don;t need to know someone’s HIV status. If you are seeing this person then talking about HIV and how you feel might help both of you.

  8. kemaerse •

    I have been with relationship to someone but havn’t known her status.what will I do?

  9. Simon Collins •

    I am sorry but this service doesn’t answer individual questions about testing and transmission. This is because the answers are already online at the FAQ page:
    http://i-base.info/qa/factsheets/hiv-transmission-and-testing

    or in this guide:
    http://i-base.info/guides/testing

  10. Gift •

    Hi i would like to know,ive been in a relationship with a lady since from last year around june until last year october ive just heard the roamers that she was HIV positive and i slep with her without a condom maybe 3 times and ive heard that she is on treatment for a long time i just wana know what are my chances of contacting HIV because we usually used condoms but sometimes not.