HIV in Canada: A primer for service providers

HIV treatment and an undetectable viral load to prevent HIV transmission

Key Points

  • The consistent and correct use of antiretroviral treatment (ART) by people living with HIV to maintain an undetectable viral load is a highly effective strategy to help prevent the transmission of HIV through sex, when sharing equipment to use drugs, or during pregnancy and birth.
  • The evidence for sexual transmission shows that people on ART who maintain an undetectable viral load do not pass HIV to their sexual partners.

HIV treatment not only improves the overall health of people living with HIV; it is also a highly effective strategy to help prevent HIV transmission.

HIV treatment, also called antiretroviral therapy (ART) works by controlling the replication of HIV in the body – that is, it reduces HIV’s ability to make copies of itself. For most people the virus becomes so well controlled that within three to six months of starting treatment the amount of virus in their blood becomes undetectable by routinely used tests. Viral load tests used in Canada cannot detect HIV in the blood if there are fewer than 40 to 50 copies of the virus per ml.

When HIV replication is controlled, the viral load in the blood and other bodily fluids (such as semen and vaginal and rectal fluids) decreases. Research tells us that as the viral load decreases, so does the risk of HIV transmission. We now know that the consistent and correct use of ART by people living with HIV to maintain an undetectable viral load is a highly effective strategy to help prevent the transmission of HIV through sex, when sharing equipment to use drugs, or during pregnancy and birth. The evidence for sexual transmission shows that people on ART who maintain an undetectable viral load do not pass HIV to their sexual partners.

For ART and an undetectable viral load to reduce the risk of HIV transmission, this strategy must be used consistently and correctly. This includes:

  • ongoing high adherence to ART medications, to achieve and maintain an undetectable viral load over time; and
  • regular medical appointments to monitor viral load and receive adherence support, if needed.

While using this prevention strategy, it is important to know that:

  • When a person first begins treatment, it usually takes three to six months for the viral load to become undetectable.
  • The viral load should remain undetectable for at least six months before depending on this approach as an effective HIV prevention strategy.
  • Some people may have trouble becoming or staying undetectable when they are on treatment. This most commonly happens when someone has low adherence to medications, but it can also occur due to drug resistance or drug toxicity.
  • Research shows that HIV transmissions can happen when a person taking ART does not have an undetectable viral load.
  • The only way to know if the viral load remains undetectable over the long term is to have regular viral load tests.
  • Regular testing and treatment (when necessary) for sexually transmitted infections (STIs) is also important since this strategy does not protect against STIs.

Resources

CATIE statement on the use of antiretroviral treatment (ART) as a highly effective strategy to maintain an undetectable viral load to prevent the sexual transmission of HIV

HIV treatment and an undetectable viral load to prevent HIV transmission – CATIE fact sheet

Treating HIV to Prevent HIV Transmission

Expert Consensus Viral Load and Risk of HIV Transmission: Summary – Institut national de santé publique du Québec

Consolidated guidelines on the use of antiretroviral drugs for treating and preventing HIV infection – World Health Organization (WHO)

Sources

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