Q and A


Is reinfection a risk if two HIV positive people are undetectable?

What are the risk involved in two HIV+ people in a couple who are both on medications and are undetectable to re infect each other during sex without a condom?

One partner (myself) has been living with HIV for a decade while my partner has been living with it less than 6 months.

I read re infection tends to be more common within the first few years of infection.

So what does the science say about two undetectable people having condomless sex?



Thanks for your question.

The two main risks from not using a condom are pregnancy and other STIs.

If these are not a concern for you, then there is no risk. This is mainly because having an undetectable viral load on treatment makes you so dramatically less infectious that HIV transmission becomes zero risk.

Even if reinfection occurred, due to viral rebound, this would only be important if one of you had drug resistance. Because your viral loads are both undetectable, neither of you have resistance to your current meds.

So long as you continue to take meds carefully and not miss doses, there is no reason that you will develop resistance in the future either.

Although it can seem strange if you are used to using condoms, many people in your situation find that not having to always use condoms can have a positive impact on their quality of life.

Please see the reports from 2017 saying that U=U (Undetectable = Untransmittable). This shows that HIV cannot be transmitted even if you don’t use condoms.

This Q&A was updated in July 2019 to an answer posted in September 2014.


  1. Roy Trevelion


    Please see this question about reinfection with different strains of HIV.

    So, there are two main types of HIV, HIV-1 and HIV-2. HIV-2 is mainly found in West Africa and is harder to get and progresses much slower. HIV-1 is the most common type of HIV. Within each types there are lots of sub-groups.

    Re-infection is only a problem when resistance to HIV medication is involved. If someone has HIV that is not resistant to any HIV medications then it is possible they can be re-infected with a virus which is resistant to one or more HIV treatments.

    But it looks as though your HIV meds are working well for you and your girlfriend. You are both undetectable with viral loads under 20. And the risk of HIV transmission when you’re undetectable is zero. Please see U=U (Undetectable = Untransmittable).

    But it’s a good idea for your girlfriend to see the doctor if her symptoms are bad. She can ask and find out what’s causing them.

  2. Olawale

    I have 2 questions

    1. Can a guy on treatment and attain less than 20 viral load reinfected with another strain when he has unprotected sex?

    2. My viral load is less than 20 and also of my fiancé, same less than 20. We have had unprotected sex for like 3 times now and recently she started complaining of headache, vomiting and shivering.

    I want to know the cause of it maybe another strains of hiv can be transmitted even if our viral loads are less than 20.

  3. Roy Trevelion

    Hi Sindisiwe,
    It’s really good you’re on HIV treatment (ART). Because once viral load has been undetectable for a few months, HIV is not transmittable – even without using condoms. Here’s a similar question “Is Undetectable = Untransmittable reall true?” with links to more info about U=U.

  4. Sindisiwe

    I tested positive and my husband negative,I’m on treatment can we have unprotected sex does the treatment affect him?

  5. Roy Trevelion

    Hello Kim,

    A CD4 count of 30 does sound low. But many people have started ARVs at low CD4 counts and then recovered well. Can you go to the clinic and ask for blood tests? This will help show how well the HIV treatment (ART) is working.

    Here’s a guide to HIV in Pictures and this page shows what happens to CD4 count and viral load when you start ART.

    Controlling your HIV can help your CD4 count to recover. And a stronger CD4 count means your immune system can begin to fight against herpes outbreaks.

    What country do you live in, do they allow gay support networks?

  6. kim

    hello everyone,
    i tested positive in may this year. i got a cd4 count of 30. of which tome it sounds very low i didn’t have any opportunistic infection. after starting to use the ARVS immediately. 4 months now i get a herpes infection this has relay caused me stress. whether i am effective to the treatment or not.
    Again am in Africa and i want to marry though i have a different orientation. stigma here is so real i don’t want to open up to anyone concerning my condition bearing in mind am gay. i therefore don’t know how i can work out my cd4 and to what level to have the undetectable viral load.
    i will appreciate help from this site thanks.

  7. Roy Trevelion

    Hi Tshidi, What is your CD4 count? Some countries used this as a guide for when to start treatment. But now UK guidelines recommend that everybody can start treatment any CD4 count. This includes CD4 counts that are higher than 500. Similar recommendations are included in the US and WHO (World Health Organisation) guidelines. You can read more about this subject here.

  8. Tshidi

    I test positive in January and my viral load 1100. When can I start using medication

  9. Roy Trevelion

    Hi Michelle, It’s good that you’re on treatment, and once your viral load becomes undetectable the risk to your husband is effectively zero. Please see the frequently asked questions here. But if you’re worried about weight loss or other symptoms it’s a good idea to talk to the doctor about them and get them checked out.

  10. Michelle

    Hi I am hiv positive I was infected 2004 i started using fdc November
    my husband is negative which we just recently got married and we having unprotected sex
    This scares me. I worry I will infect him and also myself will not see any improvement I’ll keep losing weight or cause more damage on my system .


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