Effect of Concurrent Partnerships and Sex-Act Rate on Gonorrhea Prevalence

The disease gonorrhea (GC) is a major public health problem in the United States, and the dynamics of the spread of GC through popula tions are complicated and not well understood. Studies have drawn attention to the effect of concurrent sexual partnerships as an influen tial factor for determining disease prevalence. However, little has been done to date to quantify the combined effects of concurrency and within-partnership sex-act rates on the prevalence of GC. This simulation study examines this issue with a simplified model of GC transmission in closed human populations that include concurrent partnerships. Two models of within-partnership sex-act rate are compared; one is a fixed sex-act rate per partnership, and the other is perhaps more realistic in that the rate depends on the number of concurrent partners. After controlling for total number of sex acts, pseudo-equilibrium prevalence is higher with the fixed sex-act rate than under the concurrency-adjusted rate in all the modeled partnership formation conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68414/2/10.1177_003754979807100404.pd

The spread and control of HIV in southern Africa

HIV has disproportionately affected southern Africa. This region, which comprises 2% of the worlds population, is home to an estimated 34% of all people living with HIV, 29% of new HIV infections globally in 2010, and 30% of AIDS-related deaths. A strengthened response to the epidemic by countries in southern Africa in recent years has brought life-prolonging antiretroviral therapy to the majority of those in need of treatment, and declines from peak levels of HIV incidence over the past decade are a reason for optimism. But, in 2010, 770,000 new HIV infections occurred. A better understanding of why the epidemic has spread so severely in this region is required to inform strategies to reduce and eventually eliminate new HIV infections. This thesis uses data analysis and mathematical modelling to understand the interaction between behavioural and biological factors that may have contributed to the spread of HIV in southern Africa, and the implications of these for controlling the epidemic. It focuses specifically on two topics of recent attention for public health decision makers in southern Africa: concurrent sexual partnerships and HIV treatment as prevention. Chapters explore the interaction between high HIV infectiousness during primary HIV infection and concurrent sexual partnerships, describe and evaluate a consensus indicator for concurrency, develop a method to adjust for high levels of missing data in sexual behaviour surveys and examine trends in sexual behaviours in a high HIV prevalence population in South Africa, create a mathematical model to examine the potential impact of antiretroviral therapy on HIV incidence in hyperendemic settings, and systematically compare the predictions of twelve different mathematical models of the impact of HIV treatment as prevention in South Africa. Taken together, through these topics we come to understand more broadly the complexity of the epidemiological context in which HIV spreads in southern Africa.Open Acces