Today’s post focuses on preventing HIV transmission in discordant couples, or “serodiscordant couples,” in which one member of the couple is HIV-positive and the other is not.

The first and perhaps simplest way to reduce rates of transmission in discordant couples is the use of barrier methods, such as condoms. However, condoms can–and sometimes do–break. It is important then for both partners in a discordant relationship to understand the risks of sexual intercourse and other ways to reduce infection from one partner to the other.

From the Centers for Disease Control and Prevention’s (CDC) website, Antiretroviral therapy (ART) is a health management method used to reduce the number of CD4 cells the HIV can bind to, thereby reducing the risk of HIV transmission. These medications are used in combination to reduce the replication of the HIV virus and treat HIV-infected persons.

HIV targets CD4 cells by:

  • Binding to the surface of CD4 cells
  • Entering CD4 cells and becoming a part of them. As CD4 cells multiply to fight infection, they also make more copies of HIV
  • Continuing to replicate, leading to a gradual decline of CD4 cells

When the number of CD4 cells are reduced, the rates of infection from one partner to another decreases. This does not mean risk of infection is eliminated, just lowered. ART and PrEP can and do reduce the rate of HIV transmission in many discordant couples, however it is not 100%. According to recent CDC articles on HIV transmission, heterosexual discordant couples treated with ART and PrEP have shown greatly reduced transmission rates. In the same article, a study conducted by the San Francisco Young Men’s Health Study, transmission rates for men who sleep with men (MSM) treated with ART were reduced by 60%.

In accordance with these findings, the CDC recommends:

“The risk of sexual HIV transmission is substantially reduced for individual couples in which the infected partner is on effective ART and has achieved undetectable plasma HIV viral load, but is not completely eliminated. Sexual transmission of HIV may still occur when the infected partner is on effective ART. In February 2008, CDC issued a statement reiterating its previous recommendations that people living with HIV who are sexually active use condoms consistently and correctly with all sexual partners.”