Does heterosexual transmission drive the HIV/AIDS epidemic in Sub-Saharan Africa (or elsewhere)?

TL;DR

This study uses a mathematical model to determine the conditions under which heterosexual contact can sustain HIV spread in Sub-Saharan Africa, highlighting critical levels of sexual activity and transmission probabilities.

Contribution

It provides a simple analytical expression for the HIV basic reproduction number based on recent data, clarifying the sexual contact thresholds for epidemic spread.

Findings

BRN exceeds 1 if individuals have 82 partners annually

BRN exceeds 1 for sex workers with about 256 clients per year

Doubling transmission probabilities significantly affects BRN

Abstract

A two-sex Basic Reproduction Number (BRN) is used to investigate the conditions under which the Human Immunodeficiency Virus (HIV) may spread through heterosexual contacts in Sub-Saharan Africa. (The BRN is the expected number of new infections generated by one infected individual; the disease spreads if the BRN is larger than 1). A simple analytical expression for the BRN is derived on the basis of recent data on survival rates, transmission probabilities, and levels of sexual activity. Baseline results show that in the population at large (characterized by equal numbers of men and women) the BRN is larger than 1 if every year each person has 82 sexual contacts with different partners. the BRN is also larger than 1 for commercial sex workers (CSWs) and their clients (two populations of different sizes) if each CSW has about 256 clients per year and each client visits one CSW every two weeks. A sensitivity analysis explores the effect on the BRN of a doubling (or a halving) of the transmission probabilities. Implications and extensions are discussed.