To the Editor.
—Dr De Cock and colleagues1 summarize data suggesting that human immunodeficiency virus type 2 (HIV2) is less transmissible through sexual intercourse than HIV-1 and conclude that this difference explains the more limited global spread of HIV-2. The authors postulate that the lesser infectivity of HIV-2 is attributable to a relatively lower viral load (and presumably lower levels of virus in semen and female genital secretions) in HIV-2—infected persons with high CD4+ lymphocyte counts compared with HIV-1—infected persons with similar values. The authors also suggest that HIV-2 may be less transmissible because late-stage disease, a period of increased viral load, develops more slowly with HIV-2 infection than with HIV-1. However, the natural history and transmissibility of these retroviruses may be linked by at least two additional factors.First, quantitative studies of HIV-1—infected persons have shown high viral levels during primary infection,2 and statistical models suggest that
O'Brien TR. HIV-2 Transmission: Implications for Spread of HIV-1. JAMA. 1994;271(12):903-904. doi:10.1001/jama.1994.03510360027021