Q and A


Is undetectable in blood the same as undetectable in genital fluids?

I have a question about having an undetectable viral load.

I read that even though your bloods may say you are undetectable, it is still possible to detect the virus in vaginal fluid or semen. Is this correct?

If so, does that mean that if you have sex without a condom (even oral) you could still pose a risk to someone and pass it on?

How is it then possible to be truly ‘undetectable’?

It seems to me that this is the problem as it’s not possible. Should I then have vaginal swabs to test for presence of the virus there?

I have been undetectable for 6 months now.


Thank you for your question.

Most people who have an undetectable viral load in their blood also have an undetectable viral load in the semen or vaginal fluid.

However, several studies have reported that this is not always the case. One in ten people with an undetectable viral load in their blood plasma are still detectable in other part of the body, including in genital fluid.

Testing viral load in genital fluids is difficult and expensive, but generally, so long as viral load is undetectable in blood, it will also be at very low levels in other compartments.

This article has more information about compartments and santuary sites.

Having an undetectable viral load dramatically reducing the risk of HIV transmission even if you are no using condoms. This would mean there is no risk of transmission from oral sex and the risk from vagainal and anal sex also get pretty close to zero.

In the PARTNER study that reported the safety of having an undetectable viral load, no linked tranmissions occured after almost 45,000 time from having sex without a condom.

This means that in practice low levels of detectable viral load in sexual fluids were not high enough to transmit HIV in this study, so long as viral load was undetectable in blood.

This answer was updated in January 2016 from a question first posted on 12 April 2011.


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