What Is HIV-2?

Genetic Strain Varies Mostly in Geographic Distribution and Disease Progression

Photo credit: National Institute of Allergy and Infectious Diseases (NIAID)

Three years after the emergence of the first cases of AIDS in the U.S., three scientists, Robert GalloLuc Montagnier and Francoise Barre-Sinoussi, discovered the virus which caused this mysterious immune deficiency syndrome, HIV.

Several years later, a new strain was found in a man living in Africa, which has genetic variations far different than the one isolated in Europe and North America. As a result, the original virus was named HIV-1 while the new strain was called HIV-2.

In biology, a strain is simply a genetic variation of an organism that makes it entirely unique. Similarities can exist but they are ultimately independent organisms. Demographically speaking, HIV-2 is a less common form of HIV with some subtle yet distinctive differences.

How are HIV-1 and HIV-2 Similar?

Despite differences in their genetic profile, HIV-1 and HIV-2 share the following similarities:

How are HIV-1 and HIV-2 Different?

There are also a number differences between HIV-1 and HIV-2. They include:

  • People with HIV-2 tend to be less infectious in the early stage of the disease compared to those with HIV-1.
  • However, HIV-2 seems to be more infectious in the later in stages disease when the CD4 count had dropped below 200 cells/mL.
  • HIV-2 is typically constrained to certain parts of the world when compared to HIV-1 (although international travel has allowed for widening global distribution)

  • The viral load test used for HIV-1 is not as reliable for people with HIV-2 infection.

  • Some antiretroviral drugs may work less effectively for people with HIV-2 although this is more related to older-generation drugs than newer ones.

Where in the World is HIV-2 Most Common?

HIV-2 is highly concentrated in West Africa countries such as Senegal, Nigeria, Ghana, and the Ivory Coast. In the past, few cases have been reported outside of these areas, but those numbers are quickly changing, particularly in HIV-2-prevalent countries popular with international travelers or those with a high influx of immigrants from HIV-2-prevalent countries.

Should I Be Tested For HIV-2?

In the past, the availability of HIV-2 testing assays was limited and only available by special request. In recent years, however, newer-generation combination tests (including the Alere Determine Combo) were released into the market, able to test not only for HIV-1 and HIV-2 but for HIV antibodies and antigens, as well.

Whether you test positive for HIV-1 and HIV-2, it is important that you always find a qualified HIV specialist.

de Cock, K. et. al. "Epidemiology and transmission of HIV-2: why there is no HIV-2 pandemic"; JAMA. 1993; 270(17): pp 2083-2086.

Palm A.; Esbjörnsson, J.; Månsson, F.; et al. "Faster progression to AIDS and AIDS-related death among seroincident individuals infected with recombinant HIV-1 A3/CRF02_AG compared with sub-subtype A3." Journal of Infectious Diseases. March 1, 2014; 209(5):721-728.

Abecasis, A.; Wensig, A.; Paraskevis, D.; et al. “HIV-1 subtype distribution and its demographic determinants in newly diagnosed patients in Europe suggest highly compartmentalized epidemics.” Retrovirology. January 14, 2013; 10:7; doi: 10.1186/1742-4690-10-7.

Continue Reading