AIDS is caused by the HIV virus, and its treatment is difficult because the virus comes in many strains, and mutations occur frequently, producing even more strains, often ones which are resistant to current medications. Multiple human immunodeficiency virus type 1 (HIV-1) genetic subtypes, intersubtype recombinants, and group O have been found in west central Africa (McCutchan et al, 1999, p. 226). In Nigeria, three major subtypes, G, A, and O, and some recombinants within these have been found. A study which looked at human immunodeficiency virus type 1 isolates from 207 patients with CD4+ cell counts less than 500/mm3 were examined for biological phenotype in MT-2 cells (Nicastri, et al, 1998, p. 90). Three subtypes of syncytium-inducing strains and two subtypes of nonsyncytium-inducing isolates were identified.
HIV infection in Brazil is one of the highest in the world, and a study characterized 43 seropositive blood units collected from volunteer blood donors living in Rio de Janeiro and looked at genetic heterogeneity (Tanuri, et al, 1999). The majority of samples contained type B or F, but their were also potential mosaic viruses of subtypes B and F or B and D. This is the first study to show genetic variations in HIV-1 in the Brazilian blood-donor population.
Swiss and U. S. scientists have found that different strains of HIV can be present in one person (Birchard, 1998, p. 1363). Teams from a hospital in Carolina and one in Switzerland studied 11 men with persistent detectable HIV-1 RNA in blood and semen before and while receiving a new antiretroviral regimen containing several anti-HIV drugs. More than half of the men had higher viral concentrations in their semen than in their blood. Men who had taken reverse transcriptase inhibitors had drug- resistant strains in their semen. Eight of ten men who had genetically analyzed HIV-1 had new resistant strains in the blood, semen or both. This paper clearly doc...