sexual HIV transmission risk if low viral load

Last edited 07/2023 and last reviewed 08/2023

Risk of sexual transmission of HIV in individuals with low-level HIV viraemia

  • review of 8 studies (7762 serodiscordant couples) found, of the 323 transmission events, none were in patients considered stably suppressed on anti-retroviral therapy, and only 2 cases of transmission when the index patient’s viral load was <1000 copies/mL (1)
    • found sexual HIV transmission to be absent in cases involving less than 600 copies per mL and exceedingly rare in cases of less than 1000 copies per m
    • in the 2 cases of transmission where the viral load was <1000 copies/mL, interpretation of both cases was complicated by long intervals (ie, 50 days and 53 days) between the transmission date and the most recent index viral load result
    • study authors conclude there is almost zero risk of sexual transmission of HIV with viral loads of <1000 copies/mL

  • commentary states that this study provides strong support for the global undetectable equals untransmittable (U=U) campaign (2)

  • systematic review does does not shed light on viral load implications for vertical transmission risk

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