Although it may be disappointing to hear, safe sex is a good idea even when both sexual partners are HIV positive, because it is possible to become infected with additional strains of HIV. This is another reason that sero-sorting is a bad idea. In addition to being ineffective at protecting HIV negative individuals from the virus, it ignores the risk of unprotected sex for the HIV positive.
It is easy for most people to understand the risks involved when an HIV positive person has sex with an HIV negative person. It is often much harder for them to comprehend that there are also risks when an HIV positive person has sex with another person with HIV. However, there are several reasons why it is still a good idea to practice safe sex even when both you and your partner are infected with HIV.
The most obvious reason that safe sex remains important is that HIV is not the only STD to which people are vulnerable. Individuals who are HIV positive can also be infected with other STDs, and being HIV infected can make some of these infections substantially worse. Being infected with HIV and another disease is known as co-infection. One particularly problematic type of co-infection occurs when someone is infected with both HIV and hepatitis C. HIV/HCV co-infection is more difficult to treat, and these patients may have more severe health outcomes in both the long and short terms.
However, unprotected sex between two HIV positive people is potentially risky even if both partners are otherwise STD free and the relationship is mutually monogamous. This is because of the potential for HIV superinfection.
HIV superinfection occurs when a person who is already infected with HIV is exposed to, and becomes infected with, a different strain of the virus. Some studies have estimated that the risk of superinfection is similar to the rate of initial infection with HIV. Superinfection is problematic because:
- It is associated with increased health problems.
- It is harder to treat, even using combined antiretroviral therapy, because there is a possibility that someone could be infected with two differently drug-resistant strains.
The fact that HIV superinfection is reasonably common also poses problems for vaccine research. It suggests that infection with one strain of HIV isn't enough to protect patients from infection with another. That makes it less likely that a vaccine will be universally, or even widely effective.
Does Treatment Matter?
If a couple are both HIV positive, and both have their infections fully suppressed with treatment, they should discuss the risks of unprotected sex with their doctors. Safe sex is still a very good idea, but treatment as prevention studies have shown that the risk of infection of an HIV-negative partner is relatively low when their regular sexual partner has an undetectable viral load. That said, that research can not necessarily be safely extrapolated to couples where both individuals are positive. There has been very little investigation of how treatment affects superinfection risk in the HIV positive. Therefore, although it is likely that effective treatment also greatly decreases superinfection risk, it would be premature to declare that it makes sex safe.
NOTE: HIV superinfection should be distinguished from dual-infection, which is defined as being infected with two HIV strains at the same time. Although HIV superinfection can lead to dual infection, it is also possible for an individual to initially be infected with two strains of HIV.
Grebely J, Oser M, Taylor LE, Dore GJ. Breaking down the barriers to hepatitis C virus (HCV) treatment among individuals with HCV/HIV coinfection: action required at the system, provider, and patient levels. J Infect Dis. 2013 Mar;207 Suppl 1:S19-25.
Kim AY, Onofrey S, Church DR. An epidemiologic update on hepatitis C infection in persons living with or at risk of HIV infection. J Infect Dis. 2013 Mar;207 Suppl 1:S1-6.
Redd AD, Quinn TC, Tobian AA. Frequency and implications of HIV superinfection. Lancet Infect Dis. 2013 May 30. doi:pii: S1473-3099(13)70066-5. 10.1016/S1473-3099(13)70066-5. [Epub ahead of print]