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Simulations of the HIV Epidemic in Sub-Saharan Africa: Sexual Transmission Versus Transmission Through Unsafe Medical Injections

French, Katherine PhD*; Riley, Steven PhD; Garnett, Geoff PhD*

Sexually Transmitted Diseases: March 2006 - Volume 33 - Issue 3 - p 127-134
doi: 10.1097/01.olq.0000204505.78077.e5

Objectives: Heterosexual transmission has long been considered the predominant route of transmission of HIV-1 in sub-Saharan Africa. However, some have argued that unsafe medical injections account for the majority of transmission in this region.

Goal: The goal of this study was to compare the HIV-1 epidemics associated with different transmission routes.

Study: An age-structured deterministic compartmental model of HIV-1 transmission through both sexual contact and unsafe injections was developed and simulations of sexual transmission and iatrogenic transmission were compared with observed prevalence.

Results: Iatrogenic transmission probabilities and numbers of unsafe injections required to generate observed prevalence are unfeasibly high. Simulations of sexually transmitted HIV-1 generate observed prevalence using transmission probabilities and average partner change rates that are within plausible bounds.

Conclusions: Heterosexual transmission seems a more likely route of transmission in the region. However, heterogeneity in contact patterns is of key importance. Further information on groups who are likely to receive more injections is required.

Simulations of sexual and iatrogenic HIV transmission found that iatrogenic transmission parameters required to generate observed epidemics are unfeasibly high, whereas sexual transmission parameters fall well within previously published ranges.

From the *Department of Infectious Disease Epidemiology, Imperial College, London, United Kingdom; and the † Department of Community Medicine, University of Hong Kong, Hong Kong

KF thanks DfID and MRC; SR thanks the Research Fund for the Control of Infectious Diseases of the Health, Welfare and Food Bureau of the Hong Kong SAR Government; and GG thanks MRC for grant support.

GG has consultations and grants for work on HSV and HPV from GSK, Sanofi Pasteur, MSD, and Merck.

Correspondence: Katherine French, PhD, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, London W2 1PG, U.K. E-mail:

Received for publication May 31, 2005, and accepted August 16, 2005.

© Copyright 2006 American Sexually Transmitted Diseases Association