Guide to Australian HIV Laws and Policies for Healthcare Professionals

Low and undetectable viral load


Viral load describes the amount of HIV present in an individual’s bloodstream. It suggests how well treatments are working and the current risk of damage to an individual’s immune system.

Low viral load is also associated with reduced HIV sexual transmission risk. With the release over recent years of findings from three key studies looking at how effectively ART prevents sexual transmission of HIV, it is now clear that for people who take ART daily as prescribed and achieve and maintain an undetectable viral load, there is effectively no risk of sexually transmitting the virus to an HIV-negative partner. This crucial message has been popularised by the global positive health campaign known as Undetectable = Untransmittable – often referred to by its abbreviation U=U. See ASHM guidance on Undetectable = Untransmittable for healthcare workers.


  1. A recent publication by ACON that aims to increase gay men’s knowledge about degrees of risk when having sex, includes the impact of low viral load in its ‘risk calculator’ (see ‘Risk Calculator’).
  2. Muessig K, Smith M, Powers K, Lo Y, Grulich A, Phillips A, Cohen M. Does ART prevent HIV transmission among MSM? AIDS 2012, 26.
  3. Vernazza P et al. Les personnes séropositives ne souffrant d’aucune autre MST et suivant un traitment antirétroviral efficace ne transmettent pas le VIH par voie sexuelle .Bulletin des médecins suisses 89 (5), (English translation, including translator’s affidavit, available here (Last accessed 1 November 2012)), 2008.
  4. HPTN-052 study. Cohen MS, Chen YQ, McCauley M, et al, Antiretroviral Therapy for the Prevention of HIV-1 Transmission, N Engl J Med, Sept 2016; 375:830-839.
  5. Partner study. Rodger AJ, Cambiano V, Bruun T, et al, Sexual Activity Without Condoms and Risk of HIV Transmission in Serodifferent Couples When the HIV- Positive Partner Is Using Suppressive Antiretroviral Therapy, JAMA, 2016;316(2):171-181
  6. Opposites Attract Study. Bavinton BR, Pinto AN, Phanuphak N, Grinsztejn B, Prestage GP, Zablotska-Manos IB, Jin F, Fairley CK, Moore R, Roth N, Bloch M, Pell C, McNulty AM, Baker D, Hoy J, Tee BK, Templeton DJ, Cooper DA, Emery S, Kelleher A, Grulich AE and The Opposites Attract Study Group. Viral suppression and HIV transmission in homosexual male serodiscordant couples: an international cohort study. In press, Lancet HIV. Accepted June 2017.