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To explore the biological similarities and differences between the HIV-1 and HIV-2 viruses, we model the probability of male-to-female transmission of either HIV virus as a function of the number of sexual partners, the prevalence of the viruses and the infectivity per contact. Using maximum likelihood estimation theory and data from a prospective study of registered female prostitutes in Dakar, Senegal, we estimate and compare the infectivities of HIV-1 and HIV-2. Graphical goodness-of-fit methods are used to show that our model fits the data well. We find that in male-to-female transmission HIV-1 is significantly more infectious than HIV-2. This finding is consistent with other data from laboratory and epidemiologic studies comparing the biology of HIV-1 and HIV-2.

Original publication




Journal article


Bulletin of mathematical biology

Publication Date





731 - 743


Department of Biostatistics, Harvard School of Public Health, Boston, MA 02115.


Humans, HIV-1, HIV-2, Acquired Immunodeficiency Syndrome, Prevalence, Models, Statistical, Probability, Cohort Studies, Prospective Studies, Mathematics, Senegal, Female, Male, Sex Work