Q and A

Question

Can I have sex with someone who is positive and not catch HIV?

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

Answer

Answer: Simon Collins

Yes, there are lots of ways to make sure HIV is not transmitted during sex.

  1. One of the easiest and most effective ways is just for the HIV positive partner to be on treatment. An undetectable viral load makes HIV untransmittable. (See: The evidence for U=U).
  2. Another relatively recent option is for the negative partner to use PrEP. This is an oral drug that when taken as prescribed is highly effective. (See: UK guide to PrEP).
  3. You can use condoms which are an effective barrier against HIV (and other STIs). Condoms need to be used carefully, preferably with plenty of lube. (See: How to use a condom (male and female).

HIV is a much less infectious virus than many other sexually transmitted infections (STI’s).

Even without a condom, the risk from a single exposure is less than, for example, 1 in 300. The actual risk becoming infected varies depending on many factors. These include the type of exposure, whether the other person is HIV positive, how high or low their viral load is, the duration and roughness of the sex etc.

If the partner is HIV positive, then viral load is the most important factor. The PARTNER study reported zero HIV transmissions after 900 couples had sex more than 58,000 times WITHOUT condoms. In this study undetectable viral load was defined as being less than 200 copies/mL.
https://i-base.info/qa-on-the-partner-study

Risk factors for penetrative sex without a condom with someone who has a very high viral load could be as high as 1 in 10 (10% risk). But the risk is effectively zero with someone who is taking treatment and who has an undetectable viral load.

This question was updated in January 2018 and November 2016 from an original answer posted in June 2007. i-Base no longer answers individual questions about HIV transmission and risk. (See: Question 1 at this link).

209 comments

  1. monicah •

    I had sex with a man. After a week I heard he might be HIV positive.
    We only had sex once. What are the chances I got infected. Would PEP help.

  2. Lisa Thorley •

    Hi Sophie,

    Please see Q1 here:

    http://i-base.info/qa/what-are-the-most-asked-questions

    It may also help to know that if the man you had sex with is on medication and his viral load is undetectable the risk of transmission is close to zero. Please see here for more info:

    http://i-base.info/qa-on-the-partner-study/

  3. sophia •

    Hi I had unprotected sex (once) a month ago and oral sex. He didn’t ejaculate inside me but a few days ago I found out he has HIV. Around 2 weeks after this encounter, I started feeling itchy in my Vulva and this was happening at night time. Then around a week ago it started itching a little during the day too and also in the anus area, although I only had vaginal and oral sex. The discharge also looks more yellow than usual. I am going for a test tomorrow and I feel very worried. Could these be signs of HIV?

  4. Lisa Thorley •

    Hi Xoli,

    You’re welcome. I’m happy that we can help.

    You’re quit right, atrozia and odimune are the same 3-in-1, this being generic versions of Atripla.

    Because you’re taking Atripla, its perfectly fine to take it a few hours after your scheduled time. I would however try not to take it too often 12hrs later. That said, data from the FOFO study has shown that taking Atripla less often is possible. Please see here for more info:

    http://i-base.info/htb/30601

  5. Xoli •

    Thank you Lisa for the response.

    I am taking Atroiza. Sometimes it’s Odimune. I believe it’s just a brand difference but I’m taking the same drug combination.

    It does happen that I forget to take the meds and will remember around midnight or when I wake up in the morning. My scheduled time is 21:00.

  6. Lisa Thorley •

    Hi Betty,

    If your brothers girlfriend was on meds before she started having sex with him, and her viral load was undetectable the risk of transmission is close to zero. Please see here for more info:

    http://i-base.info/qa-on-the-partner-study/

  7. Betty •

    Hi
    My brother just found out the girlfriend she’s been dating is HIV positive and she never told him they had an unprotected sex countless time she got preg, its been a year since they have been dating my brother found out when she saw her taking meds! What are the chances of him getting infected if she’s been on meds long before they even met?

  8. Lisa Thorley •

    Hi Goodman,

    Please see Q1 here:

    http://i-base.info/qa/what-are-the-most-asked-questions

    Also, if you are worried you should ask her if she’s on treatment.

    You may also still be in for PEP.Please see here:

    http://i-base.info/pep-and-prep/

  9. Goodman •

    I had unprotected sex with person who has HIV. This was less than 24 hours ago. Is it possible I can prevent being infected? I don’t know her viral load and I released outside.

  10. Lisa Thorley •

    Hi Xoli,

    Viral loads once undetectable usually stay undetectable. If they are to increase, it could be a temporary blip, or there has been drug resistance.

    Other than taking meds, there isn’t anything that you can do to prevent this from happening.

    With regards to the time that you take your meds, this will depend on what meds you’re taking. If you could let me know what you take I’ll be able to tell you how strictly you need to adhere to them.