Health Sexual Health Safer sex What is HIV-undetectable? What is HIV-undetectable? HIV-undetectable is a term used to describe someone who is living with HIV but on successful and effective treatment. Someone who is HIV-undetectable cannot pass on the virus through sex. Usually after someone is diagnosed with HIV they are put on treatment straight away, within a short period of time the medicine kicks in and that person's viral load (the amount of HIV in the body) begins to drop. Once it goes under a certain level they become 'undetectable', meaning that the amount of HIV in their body is so low that it will not show up on test. However, once they become HIV-undetectable then they cannot pass on the virus to anyone. The most recenty study (PARTNER2) recruited and monitored gay couples between 2010-18, where one was HIV-undetectable and the other HIV-negative. There were 782 couples elligble for the study who had condomless anal sex 76,000 times and the study found no transmission of HIV between the couples.The first PARTNER Study (2010-2014) monitored condomless sex between over 1,000 gay and straight couples where one was HIV-undetectable and the other HIV-negative. After these couples had condomless sex over 58,000 times the study found no transmission of HIV between the couples. Does being undetectable mean safer sex? All studies suggest that someone who is undetectable on effective treatment is not infectious. The PARTNER study found no cases of HIV transmission from an HIV-positive partner on treatment whose viral load was low enough to be considered undetectable. This remained the case even when other STIs were present. Researchers are cautious about saying that any prevention method is 100% effective however the weight of evidence that undetectable means uninfectious (U=U) is growing. People do not become undetectable immediately when they go on treatment and their viral load may fluctuate, particularly early on. For this reason, the recommendation is that someone should be undetectable for six months before expecting this to mean uninfectious. Being HIV-undetectable for HIV does not mean that someone won’t pass on other STIs. Using condoms and lube will prevent transmission of a wide range of infections. What is viral load and how does it impact risk? Viral load refers to the amount of HIV a person has in their blood, cum and anal mucus The lower the viral load, the less infectious the HIV-positive person will be People who have been diagnosed with HIV are encouraged to have regular blood tests Looking at viral load in the blood helps doctors monitor someone’s progress, e.g. to see if the drugs are working for him If HIV treatment is successful, someone's viral load will become so low that it will be undetectable. Someone who has not been diagnosed or who is not on treatment is likely to have a higher viral load than someone who is on treatment. Viral load is particularly high just after someone has been infected with HIV and so if someone has only recently been infected, they will be more likely to pass the virus on to their sexual partners if they have unprotected sex What is viral load and what does HIV-undetectable mean? Watch this video as we explain what 'viral load' means LAST UPDATE: 03/05/2019 BACK TO HIV, AIDS & SAFER SEX UNPROTECTED SEX HOW IS HIV TRANSMITTED? References Read more (1) PHE: HIV in the UK – Situation Report 2015 Incidence, prevalence and prevention) (2) Zuckerman RA, Whittington WLH, Celum CL, Collis TK, Lucchetti AJ, Sanchez JL, Hughes JP, Sanchez JL, Coombs RW. Higher concentrations of HIV RNA in rectal mucosa secretions than in blood and seminal plasma, among men who have sex with men, independent of antiretroviral therapy. Journal of Infectious Diseases, 2004;189:156-161. (3) Rodger A et al. HIV transmission risk through condomless sex if HIV+ partner on suppressive ART: PARTNER study. 21st Conference on Retroviruses and Opportunistic Infections, Boston, abstract 153LB, 2014.