The influence of different sexual-contact patterns between age classes on the predicted demographic impact of AIDS in developing countries
Anderson, R.M.; Ng, T.W.; Boily, M.C.; May, R.M.
Annals of the new York Academy of Sciences 569: 240-274
1989
ISSN/ISBN: 0077-8923 PMID: 2698092 DOI: 10.1111/j.1749-6632.1989.tb27374.xDocument Number: 371204
A mathematical model of the likely demographic impact of acquired immunodeficiency syndrome (AIDS) suggest that, in the countries of sub- Saharan Africa, this impact can be expected to increase in the years ahead as a result of unequal transmission probabilities (weighted toward a greater probability from males to females) and the tendency of men to select female sexual partners from a younger class. The model refines earlier work in its consideration of predicted influence of human immunodeficiency virus (HIV) infection on the age structure and dependency ratio of the population, the significance of patterns of sexual contact between the age classes of the 2 sexes, and the impact of control measures such as health education and condom use. The assumptions of a doubling time of 1.5 years in the early stages of the epidemic and a 3 times greater probability of transmission from infected males to susceptible females rather than vice versa produce the observation that net population growth rate will change from positive to negative 25 years after introduction of the AIDS virus. The dependency ration is not significantly affected by AIDS due to the counterbalancing effects of deaths from vertical and horizontal transmission. On the other hand, if dependency ratio is defined to encompass the burden created by the care of AIDS patients, the disease-related ratio will increase over time. The most significant social factor in terms of the impact of AIDS on net fertility is the tendency of African men to choose female sexual partners at least 5 years younger than themselves. Finally, the numerical analyses indicate that the introduction of AIDS control measures 10 years after the onset of the epidemic will slow the progression of the epidemic and prevent a change in the population growth rate from positive to negative over a 100-year period.