Treatment and sexual transmission risk

  • An undetectable viral load in someone taking treatment may be more protective than an undetectable viral load in someone not taking treatment.
  • Studies which have followed heterosexuals taking treatment who have an undetectable viral load have not observed any transmission events.
  • However sexual transmission between men has been reported.

For those who can access them, HIV treatments have had a major impact on the health and lifespan of HIV-positive individuals. For most people, HIV treatments can reduce the amount of HIV in the body to very low levels. When the number is below the limit of detection, usually 40 or 50 copies of HIV’s genetic material (RNA) in each millilitre of blood, viral load is said to be 'undetectable'.

An undetectable viral load is the primary aim of treatment since this reduces the risk of drug resistance and gives the immune system a chance to recover and restore itself (as measured by CD4 cell counts).  The higher the CD4 count, the lower the risk of becoming ill with HIV-related illnesses.

There may be a difference in the risk of transmission between people who have undetectable viral load but are not taking treatment, and people who have undetectable viral load while on combination therapy. The penetration of antiretrovirals in the genital tract may be important here. It appears that in untreated people, viral load in blood plasma is less reliably correlated with viral load in the genital tract.

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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.