Understanding the epidemic of HIV in South Africa. Analysis of the antenatal clinic survey data.

OBJECTIVES

To investigate the magnitude and the time course of the HIV epidemic in the provinces of South Africa from the antenatal clinic HIV surveys.

DESIGN

We analysed the data on the provincial prevalences of HIV infection from 1990 to 1996 using maximum likelihood methods to determine the intrinsic growth rate and probable asymptotic prevalence of HIV among women attending antenatal clinics.

SUBJECTS

Women attending antenatal clinics and included in the national HIV prevalence surveys conducted by the Department of Health.

RESULTS

1. In KwaZulu-Natal the epidemic is likely to peak at a prevalence of about 23% (95% confidence interval (CI) 19-36%). 2. The intrinsic doubling time does not differ significantly among the provinces. 3. The average length of the intrinsic doubling time is 12.0 months (95% CI 11.3-12.8 months). 4. The force of infection is approximately 1.00/year at age 16 years and declines at a rate of about 5% per year of age above 16 years.

CONCLUSIONS

South Africa is likely to experience one of the worst HIV epidemics in Africa. The lack of statistically significant differences between the growth rates of the epidemic in the various provinces constrains the possible explanations that can be advanced to explain the time course of the epidemic and may in part be a consequence of migrancy. The intrinsic growth rate is higher than previous estimates and it is possible that in those provinces where the prevalence is still low it will eventually reach the same levels as in KwaZulu-Natal.