This diversity is a result of its fast replication cycle, with the generation of about 1010 virions every day, coupled with a high mutation rate of approximately 3 x 10−5 per nucleotide base per cycle of replication and recombinogenic properties of reverse transcriptase.This complex scenario leads to the generation of many variants of HIV in a single infected patient in the course of one day. This variability is compounded when a single cell is simultaneously infected by two or more different strains of HIV. When simultaneous infection occurs, the genome of progeny virions may be composed of RNA strands from two different strains. This hybrid virion then infects a new cell where it undergoes replication. As this happens, the reverse transcriptase, by jumping back and forth between the two different RNA templates, will generate a newly synthesized retroviral DNA sequence that is a recombinant between the two parental genomes. This recombination is most obvious when it occurs between subtypes.The closely related simian immunodeficiency virus (SIV) has evolved into many strains, classified by the natural host species. SIV strains of the African green monkey (SIVagm) and sooty mangabey (SIVsmm) are thought to have a long evolutionary history with their hosts.
Research
HIV/AIDS research includes all medical research that attempts to prevent, treat, or cure HIV/AIDS, as well as fundamental research about the nature of HIV as an infectious agent and AIDS as the disease caused by HIV. Many governments and research institutions participate in HIV/AIDS research. This research includes behavioral health interventions, such as research into sex education, and drug development, such as research into microbicides for sexually transmitted diseases, HIV vaccines, and anti-retroviral drugs. Other medical research areas include the topics of pre-exposure prophylaxis, post-exposure prophylaxis, circumcision and HIV, and accelerated aging effects. Treatment and transmission
The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs. In many parts of the world, HIV has become a chronic condition in which progression to AIDS is increasingly rare. HIV latency, and the consequent viral reservoir in CD4+ T cells, dendritic cells, as well as macrophages, is the main barrier to eradication of the virus.It is important to note that although HIV is highly virulent, transmission does not occur through sex when an HIV-positive person has a consistently undetectable viral load (<50 copies/ml) due to anti-retroviral treatment. This was first argued by the Swiss Federal Commission for AIDS/HIV in 2008 in the Swiss Statement, though the statement was controversial at the time. However, following multiple studies, it became clear that the chance of passing on HIV through sex is effectively zero where the HIV-positive person has a consistently undetectable viral load; this is known as U=U, "Undetectable=Untransmittable", also phrased as "cant pass it on".