Sexual HIV transmission risk if low viral load

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

Reference:

• Broyles LN et al. The risk of sexual transmission of HIV in individuals with low-level HIV viraemia: a systematic review. Lancet July 22nd 2023 https://doi.org/10.1016/S0140-6736(23)00877-2
• Bekker L et al. HIV is sexually untransmittable when viral load is undetectable. Lancet July 22nd 2023 https://doi.org/10.1016/S0140-6736(23)01519-2