Undetectable = Untransmittable

Did you know? When a person is on antiretroviral treatment, and that this one has an undetectable viral load, it can no longer transmit the HIV virus.

Equation referring to U=U

This scientific evidence is also known as “Undetectable = Intransmissible”.

Undetectable means that the viral load, or the amount of virus in the blood, is at a very low level.

Intransmissible means that when the viral load is undetectable, HIV cannot be sexually transmitted.

A simple formula:

HIV + Effective treatment = undetectable

viral load Undetectable viral load = 0 sexual transmission

0 sexual transmission = intransmissible


undetectable = untransmittable

Equation recognized in Quebec and Canada

The Ministry of Health and Social Services of Quebec published a ministerial position in October 2018 on “The effect of the treatment of people living with HIV on the risk of sexual transmission of the infection” stipulating:

There is no evidence of transmission of HIV infection during oral, vaginal or anal sex without a condom, under these two conditions :

  • when the person living with HIV is taking antiretroviral therapy as prescribed


  • that his viral load, measured by consecutive laboratory tests every four to six months, remains at less than 200 copies per milliliter of blood.

In this context, the risk of transmission is negligible. (For public health, “negligible” means there is a theoretical potential for transmission, but zero reported cases.)

Resources on undetectable viral load and the sexual transmission of HIV

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