HIV-2

  • HIV-1 and HIV-2 are two different viruses.
  • Globally, the vast majority of infections are of HIV-1, but HIV-2 is prevalent in West Africa.
  • HIV-2 is less infectious than HIV-1.

HIV-1 and HIV-2 are distinct retroviruses originating from two different primate species.1 Transmission modes for both strains are the same, and infection with either strain can lead to the development of AIDS.2

However treatment strategies are different – NNRTIs are not active against HIV-2, a number of other drugs are less effective, and pregnancy should be managed differently.

The origin of HIV-2 is attributed to the sooty mangabey monkey. There are at least eight identified subtypes of HIV-2, but only subtypes A and B are commonly found. Although the majority of HIV-2 infections have been found in West Africa, the number of diagnosed cases in India is increasing. HIV-2 cases are also found in European countries with former colonial ties (particularly Portugal and France) to West Africa. Incidence of HIV-2 infection remains low in the UK (144 HIV-2 mono-infections and 22 HIV-1 and 2 dual infections).

A persistent lower viral load is one reason for a lower incidence rate and transmission risk in HIV-2 infection than is found in HIV-1.3

In general, after HIV-2 seroconversion, the viral load tends to remain low for a longer period than is typically found in HIV-1 infection. Approximately 5 to 15% of people infected with HIV-1 are considered to be long-term non-progressors versus 86 to 95% of people infected with HIV-2.4

The virulence of HIV-2 is considerably less than that of HIV-1, resulting in lower HIV-2 transmission rates, a slower course of infection, and delayed progression to AIDS.5 In the later stages of AIDS, HIV-2 infectiousness does increase, but for a shorter duration than is seen with HIV-1 infection.

An early prospective study of over 1100 infants born to HIV-1 and HIV-2 infected women showed that vertical transmission took place in 21% of the infants with HIV-1 infected mothers within the first 18 months while no transmission was seen in infants born to HIV-2 infected mothers.6

A study looking at a cohort of 250 women, almost equally divided between those with HIV-1 and HIV-2, found that over a period of four years, six of the HIV-2 infected women went on to acquire HIV-1 infection. In contrast, none of the women who originally tested positive for HIV-1 became reactive to HIV-2.7 This dispels the idea once held that persons with HIV-2 might have a protective benefit against acquiring HIV-1.

Testing for HIV-2 infection is covered in a later section.

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References

  1. Hahn BH et al. AIDS as a Zoonosis: Scientific and Public Health Implications. Science 287(5453): 607-614, 2000
  2. Jaffar S et al. The natural history of HIV-1 and HIV-2 infections in adults in Africa: a literature review. Bull World Health Organ 82(6):462-9, 2004
  3. Martinez-Steele E et al. Is HIV-2-induced AIDS different from HIV-1-associated AIDS? Data from a West African clinic. AIDS 21(3): 317-324, 2007
  4. Kanki P Human Immunodeficiency Virus Type 2 (HIV-2). AIDS Rev 1: 101-108, 1999
  5. Marlink R et al. Reduced rate of disease development after HIV-2 infection as compared to HIV-1. Science 265(5178): 1587-1590, 1994
  6. The HIV Infection in Newborns French Collaborative Study Group Comparison of vertical human immunodeficiency virus type 2 and human immunodeficiency virus type 1 transmission in the French prospective cohort. Pediatr Infect Dis J, 13(6): 502-506, 1994
  7. Wiktor SZ et al. Lack of protection against HIV-1 infection among women with HIV-2 infection. AIDS 13(6): 695-699, 1999
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.