STD Awareness: Do Sexually Transmitted Diseases Increase HIV Risk?

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virion HIVYou might have heard that having an STD like syphilis, herpes, or gonorrhea can make it easier to catch HIV, the virus that causes AIDS. But have you ever wondered if this was true? Maybe it’s just a simple correlation — for example, someone who doesn’t practice safer sex would be more likely to catch HIV along with any other STD. That doesn’t mean that one causes the other, does it?

Common STDs like herpes and trichomoniasis can increase HIV risk.

But it’s not a mere correlation. If you take one person with an STD and one person without an STD and expose them both to HIV through sexual contact, the person with the STD will be at least two to five times more likely to become infected with HIV. Why is that? First, many STDs can make you more susceptible to an HIV infection. Second, the immune response triggered by many sexually transmitted infections can summon the types of immune cells that HIV targets.

Furthermore, if a person with HIV is co-infected with another STD, he or she is more likely to transmit HIV to a partner. In other words, STDs can make a person with HIV more infectious. HIV is more likely to appear in their genital secretions, making it easier to transmit HIV through sexual activity.

Some STDs cause ulcers, which are open sores. Normally, our intact skin provides our first defense against microbial invaders, and it’s a very effective armor indeed. When there are open sores, however, viruses like HIV can more easily penetrate our first defense, making us more vulnerable to infection. Below we will discuss two common “ulcerative” STDs, and how they might increase risk for HIV.

  • Herpes: A genital herpes (HSV-2) infection increases HIV risk via two mechanisms: First, during an outbreak, an immune response is triggered, during which CD4+ cells are called onto the scene. These cells are targets for HIV. Secondly, the ulcers that appear during an outbreak create tiny tears in the body, which make it easy for HIV particles to enter our bodies. When someone experiencing a herpes outbreak is sexually exposed to HIV, he or she is two to four times more likely to acquire an HIV infection than someone who is not experiencing an outbreak — that’s because the sores create openings through which microscopic HIV particles can pass. If someone with HIV is also experiencing a herpes outbreak, he or she is more likely to expose a sexual partner to HIV because herpes sores can bleed.
  • Syphilis: Just as with herpes, syphilis can cause genital sores that make someone more likely to acquire or transmit HIV to a sexual partner. People with syphilis are two to five times more likely to acquire HIV when exposed to it sexually than they would be if they didn’t have a syphilis infection. Additionally, someone with an HIV infection will have a higher viral load when co-infected with syphilis.

Other STDs are “non-ulcerative,” meaning that they don’t cause open sores. However, they can still cause inflammation, which recruits CD4+ immune cells to fight infection. With more CD4+ cells at the scene of the infection, there are more cells for HIV to target, increasing its chance of successfully infecting a new host. Some of the following non-ulcerative STDs cause inflammation and are known to increase risk for HIV:

  • Chlamydia: This STD often has no symptoms, and when it goes untreated, it can increase risk for acquiring or transmitting HIV.
  • Gonorrhea: Just like chlamydia, gonorrhea often has no symptoms, and when it’s not treated, it can increase risk for acquiring or transmitting HIV. For example, an HIV-positive man with gonorrhea can have 10 times as much HIV in his semen as an HIV-positive man without gonorrhea.
  • Trichomoniasis: Have you heard of trichomoniasis — trich for short? It’s the most common curable STD is the country, infecting an estimated 3.7 million Americans at a time. It can cause inflammation in the genital area, which can increase risk for both acquiring and transmitting HIV from or to a partner. Women with trich are two to three times more likely to acquire an HIV infection when sexually exposed to the virus — in fact, one study estimated that 6.2 percent of all HIV infections among American women could be attributed to trich. HIV-positive men with a trich infection in their urethras have eight times more HIV in their semen than do HIV-positive men whose urethras are not inflamed by a trich infection, meaning that it’s easier to catch HIV from a man with trich than from a man without trich.

Strategies to reduce your risk of HIV infection include:

  • getting screened for STDs regularly, and treated if necessary
  • abstaining from sexual activity
  • limiting your number of sexual partners
  • using barrier methods such as latex condoms, female condoms, and dental dams (note: lambskin condoms are not effective in preventing STD transmission)
  • avoiding contact with blood, for example by abstaining from sharing needles if injecting drugs
  • asking a doctor about post-exposure prophylaxis (PEP) immediately after you might have been exposed to HIV — as it is not 100 percent effective and comes with side effects, PEP is viewed as a last resort

Testing for all STDs, including HIV, is available at any Planned Parenthood health center, as well as from most physicians, hospitals, and clinics. Local, state, and federal health departments may offer free testing. The CDC has a tool to locate a testing location near you.

Click here to check out other installments of our monthly STD Awareness series!