The Differences Between HIV-1 and HIV-2

The Human Immunodeficiency Virus (HIV) has two main strains, HIV-1 and HIV-2. These two strains of HIV are very similar, but they have a few distinct characteristics that set them apart.

HIV-1 vs HIV-2

This strain is found worldwide and is more common.This strain is found predominantly in West Africa.
This strain is more likely to progress and worsen.This strain is less likely to progress and many of those infected remain lifelong non-progressors. Progression is slower.
Average level of immune system activation are higher.Average level of immune system activation are lower.
During progression, HIV-1 has lower CD4 counts than HIV-2.During progression, CD4 counts are higher in this strain.
Plasma viral loads are higher.Plasma viral loads are lower.

Overall, HIV-1 and HIV-2 share many traits, including how they are transmitted and contracted, their basic genetic makeup, and that both follow similar pathological processes and develop into AIDS (Acquired Immune Deficiency Syndrome). Typically, when you hear HIV mentioned in general, it is in regards to HIV-1 since it is far more prevalent.

HIV-1 is further classified into four groups: M (the major group), N, O (the outlier group), and P. More than 90 percent of HIV-1 cases involve HIV-1 group M. Within group M lie 10 separate subtypes: A, B, C, D, F, G, H, J, and K, also included are CRFs (circulating recombinant forms) which are essentially hybrid subtypes formed from a mixture of two subtypes; think of them as sub-subtypes.


Subtypes A and C are the most widespread geographically, however, subtype B is the most common subtype in Japan, the Americas, Europe and Australia.

STDcheck offers the fourth generation ELISA HIV test which reliably detects between both HIV-1 and HIV-2 strains, whereas many other HIV tests commonly test for HIV-1 alone. Our fourth generation test can also detect infections with rare groups and subtypes. We also offer the HIV RNA Early Detection test, which can detect the HIV virus’s genetic material as early as only 9-11 days after potential exposure.

Medically Reviewed by on September 21, 2018

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Author: Nick Corlis

Nick Corlis is a writer, marketer, and designer. He graduated from Texas State University in San Marcos, Texas, with a degree in Digital Communications. Nick is proud to be able to help eliminate the stigma of STD testing through his writing and is always trying to advocate the importance of your sexual health. Before STDcheck, his favorite way to develop his writing skills was by accepting various writing jobs in college and maintaining multiple blogs. Nick wears many hats here at STDcheck, but specifically enjoys writing accurate, well-researched content that is not only informative and relatable but sometimes also contains memes. When not writing, Nick likes to race cars and go-karts, eat Japanese food, and play games on his computer.