HIV is a virus that weakens the immune system. There are two main types of this virus: HIV-1 and HIV-2.
Both types of HIV are long-term but manageable health conditions. With effective treatment, people with HIV can live long, healthy lives.
Understanding the different types of HIV helps increase awareness of the condition. In this article, we explore the differences and similarities between HIV-1 and HIV-2.
Geography and genetics
HIV-1 is the most common type of HIV and occurs all over the world. According to the HIV awareness charity Avert, around 95 percent of people living with HIV have HIV-1.
HIV-2 is mainly present in West Africa, but it is slowly starting to appear in other regions, including the United States, Europe, and India.
Though HIV-1 and HIV-2 are both retroviruses that can have similar effects on the human body, they are genetically distinct. A 2008 study revealed that the genomes of the two viruses only had a 55 percent sequence identity.
This means that not all tests and treatments work for both types of HIV.
HIV-2 is harder for people to transmit than HIV-1. According to one 2013 review, the most common mode of HIV-2 transmission is heterosexual sex. However, heterosexual transmission rates of HIV-2 are five to 10 times lower than those of HIV-1.
Between mothers and babies, transmission rates of HIV-2 are 20–30 times lower than those of HIV-1.
A person can contract either type of HIV through direct contact with bodily fluids that contain the virus,
- sexual fluids
- breast milk
Risk factors for HIV-1 and HIV-2 transmission include sex without a condom and sharing needles or syringes.
However, there is little risk of transmitting HIV through sex if a person takes HIV medications correctly and is able to maintain an undetectable viral load. This can also significantly reduce the risk of mother-to-child transmission.
The genetic differences between HIV-1 and HIV-2 mean that if a person takes a test for HIV-1, it may not detect HIV-2. For people at increased risk of HIV-2, a healthcare provider may also test for HIV-2 antibodies or antigens.
To treat HIV, a healthcare provider usually prescribes a combination of several medications called antiretroviral therapy. Taking these medications daily as they instruct can slow progression of HIV, prevent transmission, and help protect the immune system.
Because of the genetic differences, a healthcare provider may prescribe different drug combinations for treating HIV-1 and HIV-2.
HIV-2 is less responsive to certain drugs that can treat HIV-1. These include:
- non-nucleoside reverse transcriptase inhibitors
Though a healthcare provider may prescribe different drug combinations, they still monitor a person’s progress in the same way. This includes checking their viral load and CD4 cell counts, as well as looking for other clinical improvements.
People with HIV-2 tend to have a lower viral load, or how much of the virus is in their blood, than people with HIV-1. Together with CD4 cell count, which is a way of determining how healthy the immune system is, viral load tells a healthcare provider how well a person’s treatment is working.
If left untreated, HIV-1 and HIV-2 both weaken a person’s immune system, leaving them more vulnerable to other infections and disease. However, HIV-2 tends to develop more slowly than HIV-1.
According to one 2011 review, people with HIV-2 may have a longer period without symptoms than people with HIV-1, and the rate of progression to stage 3 HIV is slower. HIV-2 also has a lower mortality rate than HIV-1.
Though there is currently no cure for either type of HIV, the development of effective treatments now means that people with HIV can live long, healthy lives.
HIV-1 and HIV-2 are the two main types of the HIV virus. Most people living with HIV have HIV-1.
Both types of HIV weaken the immune system, but HIV-2 tends develop more slowly and is less easy for people to transmit than HIV-1.
Genetic differences between the two viruses means that there are some differences in how healthcare providers diagnose and treat HIV-1 and HIV-2.
Medically reviewed by Deborah Weatherspoon, Ph.D., R.N., CRNA
Written by Lana Burgess