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
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.
Hi Richi,
Please see Q1 here:
https://i-base.info/qa/what-are-the-most-asked-questions
I had sex with a girls whose status I don’t know, the condom broke.
Hi Lungile,
If you’re partner is on treatment and has an undetectable viral load, the risk of transmission is close to zero. Please see the results of the PARTNER study for more info:
https://i-base.info/qa-on-the-partner-study/
If you’re worried, you will need to test. Please see Q1 here:
https://i-base.info/qa/what-are-the-most-asked-questions
I had sex unprotected and my partner takes treatment very seriously and I have not felt any changes in my body, any chances I might be infected?. It’s been three months now.
Hi None,
Please see Q’s 1 and 5 here:
https://i-base.info/qa/what-are-the-most-asked-questions
I was in an 8 month relationship with a male who is HIV positive. He found out about 5 months after we split up that he had it for about 11 years. I work on an ambulance and had stuck myself with a dirty needle 4 months after we broke up and was tested for all bloodborn diseases and came back clear… Am I being overly paranoid? Could I have numbers so low they weren’t able to count them? It had been over a year from the first time we had unprotected sex to when I was tested.
Hi Mark,
If the guy you had sex with is on treatment and is undetectable, then the risk would have been close to zero. Please see the results of the PARTNER study for more info:
https://i-base.info/qa-on-the-partner-study/
If you don’t know this, then if you had sex within the last 48, max 72 hours you could take PEP. If this isn’t a possibility, then you will need to test. Please see Q1 here for testing info:
https://i-base.info/qa/what-are-the-most-asked-questions
Ok so I had sex with a guy (I’m gay) he has HIV and I didn’t know he had it before we had sex. The condom broke, what should I do?
Hi David,
Please see question 1 here:
https://i-base.info/qa/what-are-the-most-asked-questions
Hi, on the 26 December I slept with a girl, I don’t know her status. The following day I started feeling weak. Its now been 30days am feeling the same weakness. On the second week went, I went for a test, but it was negative can i be infected?