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.

HIV-1 is the most common type of HIV, and it occurs all over the world. According to the HIV awareness charity Avert, around 95% 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% 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 review, the most common mode of HIV-2 transmission is sex between cisgender heterosexual people. However, rates of HIV-2 transmission among cisgender heterosexuals are about five times lower than those of HIV-1.

Between birthing parents 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, including:

  • blood
  • 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 means that there are such small quantities of HIV in the blood that tests cannot detect it.

Taking medication as prescribed and maintaining an undetectable viral load also significantly reduce the risk of transmission from a pregnant parent to a child.


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 professional may also test for HIV-2 antibodies or antigens.

For more in-depth information and resources on HIV and AIDS, visit our dedicated hub.

To treat HIV, a healthcare professional usually prescribes a combination of several medications called antiretroviral therapy. Taking these medications daily as instructed can slow the progression of HIV, prevent transmission, and help protect the immune system.

Because of the genetic differences, a doctor may prescribe different drug combinations for treating HIV-1 and HIV-2.

HIV-2 is resistant to certain drugs that can treat HIV-1. These include:

  • non-nucleoside reverse transcriptase inhibitors
  • enfuvirtide

Though a doctor may prescribe different drug combinations, they still monitor a person’s progress in the same way. This includes checking their viral load and looking for other clinical improvements. Doctors also check CD4 cell counts, which is a way of determining how healthy the immune system is.

People with HIV-2 tend to have a lower viral load than people with HIV-1. Together with CD4 cell count, viral load tells a healthcare professional how well a person’s treatment is working.

Left untreated, both HIV-1 and HIV-2 can weaken a person’s immune system, leaving them more vulnerable to other infections and diseases. 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 most common subtypes of this virus. Most people living with HIV have HIV-1.

While both types of HIV weaken the immune system, HIV-2 tends to develop more slowly and has a lower rate of transmission than HIV-1.

Genetic differences between the two viruses mean that there are some differences in how doctors diagnose and treat HIV-1 and HIV-2.

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