Estimation of the HIV basic reproduction number in rural South West Uganda: 1991-2008

Abstract

Background: The basic reproduction number, R0, is one of the many measures of the epidemic potential of an infection in a population. We estimate HIV R0 over 18 years in a rural population in Uganda, examine method-specific differences in estimated R0, and estimate behavioural changes that would reduce R0 below one. Methods: Data on HIV natural history and infectiousness were collated from literature. Data on new sexual partner count were available from a rural clinical cohort in Uganda over 1991-2008. R0 was estimated using six methods. Behavioural changes required to reduce R0 below one were calculated. Results: Reported number of new partners per year was 0 to 16 (women) and 0 to 80 (men). When proportionate sexual mixing was assumed, the different methods yielded comparable R0 estimates. Assuming totally assortative mixing led to increased R0 estimates in the high sexual activity class while all estimates in the low-activity class were below one. Using the "effective" partner change rate introduced by Anderson and colleagues resulted in R0 estimates all above one except in the lowest sexual activity class. R0 could be reduced below one if: (a) medium risk individuals reduce their partner acquisition rate by 70% and higher risk individuals reduce their partner acquisition rate by 93%, or (b) higher risk individuals reduce the partner acquisition rate by 95%. Conclusions: The estimated R0 depended strongly on the method used. Ignoring variation in sexual activity leads to an underestimation of R0. Relying on behaviour change alone to eradicate HIV may require unrealistically large reductions in risk behaviour, even though for a small proportion of the population. To control HIV, complementary prevention strategies such as male circumcision and HIV treatment services need rapid scale up. © 2014 Nsubuga et al.