title: Epidemiology and transmission of HIV-2. Why there is no HIV-2 pandemic.
abstract: Although human immunodeficiency virus type 1 (HIV-1) and HIV-2 share modes of transmission, their epidemiologic characteristics differ and international spread of HIV-2 has been very limited. Recently, the prevalence of infection with HIV-1 but not HIV-2 has increased rapidly in different West African countries, where HIV-2 was probably present earlier. Among 19,701 women of reproductive age tested in Abidjan, Ivory Coast, between 1988 and 1992, the prevalence of HIV-1 infection increased from 5.0% to 9.2%, while that of HIV-2 declined from 2.6% to 1.5%. Differences in viral load may be responsible: reported results of virus culture and polymerase chain reaction assays suggest that at high CD4+ T-lymphocyte counts viral load is lower in HIV-2-infected than in HIV-1-infected persons; the efficacy of heterosexual and perinatal transmission of HIV-2 is less efficient than that of HIV-1 at this stage. At low (< 0.20 x 10(9)/L [< 200/microL]) CD4+ T-lymphocyte counts, virus isolation is equally successful for both viruses, and the efficacy of heterosexual transmission is similar. Differences in HIV-1 and HIV-2 natural history are reflected in differences in viral load, that for HIV-2 being lower until immunodeficiency is severe. Differences in viral load throughout most of the natural history of infection appear to correlate with lower transmissibility of HIV-2 than HIV-1, and are the likeliest explanation for their markedly different global epidemiology.
authors.affiliation: Projet RETRO-Cl, Abidjan, Ivory Coast.
authors.forename: K M
authors.initials: KM
authors.lastname: De Cock
authors.forename: G
authors.initials: G
authors.lastname: Adjorlolo
authors.forename: E
authors.initials: E
authors.lastname: Ekpini
authors.forename: T
authors.initials: T
authors.lastname: Sibailly
authors.forename: J
authors.initials: J
authors.lastname: Kouadio
authors.forename: M
authors.initials: M
authors.lastname: Maran
authors.forename: K
authors.initials: K
authors.lastname: Brattegaard
authors.forename: K M
authors.initials: KM
authors.lastname: Vetter
authors.forename: R
authors.initials: R
authors.lastname: Doorly
authors.forename: H D
authors.initials: HD
authors.lastname: Gayle
mesh_terms: D000293:Adolescent; D000328:Adult; D000354:Africa, Western / Q000453:epidemiology; D005260:Female; D014943:Global Health; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission*; D015497:HIV-1 / Q000472:pathogenicity; D015498:HIV-2 / Q000472:pathogenicity; D006801:Humans; D015994:Incidence; D008297:Male; D015995:Prevalence; D015229:Sexually Transmitted Diseases, Viral / Q000453:epidemiology / Q000635:transmission