How does the global distribution of HIV species vary?

Updated: Jul 27, 2020
  • Author: Shelley A Gilroy, MD, FACP, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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Two distinct species of HIV (HIV-1 and HIV-2) have been identified, and each is composed of multiple subtypes, or clades. All clades of HIV-1 tend to cause similar disease, but the global distribution of the clades differs. This may have implications on any future vaccine, as the B clade, which is predominant in the developed world (where the large pharmaceutical companies are located), is rarely found in the developing countries that are more severely affected by the disease.

HIV-1 probably originated from one or more cross-species transfers from chimpanzees in central Africa. [14] HIV-2 is closely related to viruses that infect sooty mangabeys in western Africa. [15] Genetically, HIV-1 and HIV-2 are superficially similar, but each contains unique genes and its own distinct replication process.

HIV-2 carries a slightly lower risk of transmission, and HIV-2 infection tends to progress more slowly to acquired immune deficiency syndrome (AIDS). This may be due to a less-aggressive infection rather than a specific property of the virus itself. Persons infected with HIV-2 tend to have a lower viral load than people with HIV-1, [16, 17] and a greater viral load is associated with more rapid progression to AIDS in HIV-1 infections. [18, 19]

HIV-2 is rare in the developed world. Consequently, most of the research and vaccine and drug development has been (perhaps unfairly) focused on HIV-1.

For information on HIV infection in children, see Pediatric HIV.

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