by EBSCO Medical Review Board

Human immunodeficiency virus (HIV) cannot be cured right now, but it can be treated with antiretroviral medicine. The medicine helps to control the virus and prevent worsening of infection to AIDs. Though HIV treatment has come a long way, it is still best to prevent the infection. HIV is mainly spread through sex with an HIV-infected person. Reducing this transmission may significantly decrease the number of people infected with HIV.

Researchers wanted to see if antiretroviral medicine can reduce the risk of passing HIV to a sexual partner. The study, published in The Lancet, found that the risk of passing on the HIV virus is completely eliminated by effective treatment of the HIV-infected partner with antiretroviral therapy.

About the Study

The prospective observational study monitored 972 gay couples where one partner was HIV positive and the other was not. The partner was receiving antiretroviral treatment.

Participants were followed up at two years to find out if the HIV-negative partner had contracted the virus. The couples reported condomless sex for an average of 1 year. In addition, 288 of the HIV-negative men reported condomless sex with other partners. By the end of the trial there were 15 new HIV infections.

The new infections were genetically tested to see if they match the specific virus of the positive partner. None of the infections were genetically linked to in-couple transmissions.

How Does This Affect You?

Antiretroviral medicine is known to reduce the effect and presence of HIV in the body. It is less clear if it can reduce the ability of the virus to infect others. Observing informed and consenting adults allowed researchers to track potential spread of HIV. This type of trial cannot confirm cause and effect, however the nature of HIV, reported habits of participants, and genetic testing show a strong link.

Antiretroviral therapy can reduce the amount of virus present in the blood, called the viral load. These low levels can make it harder for the virus to pass to other people. If you or your partner has HIV, talk to your doctor about steps that can be taken to prevent spreading the virus. Sticking with recommended treatment can be a benefit for both. Some periods of time can lead to higher viral loads, when the virus may be easier to pass. Condom use can also help to prevent the spread of HIV.

RESOURCES—US Department of Health and Human Services 

World Health Organization 


Roger A, et al. Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study. Lancet 2019 June, 393:10189, 2428-2438.

Overview of HIV infection. EBSCO DynaMed website. Available at: . Updated November 30, 2018. Updated May 6, 2019.

Revision Information

  • Reviewer: EBSCO Medical Review Board
  • Review Date: 04/2019