Biostatistical Analysis of HIV/AIDS Prevalence Trends in Anambra State Using Logistic Growth Models

HIV/AIDS prevalence monitoring in Anambra State, South East Nigeria, is essential for evaluating the effectiveness of antiretroviral therapy scale-up and prevention programmes implemented under the National HIV/AIDS Strategic Plan. This study employs the logistic growth model and its modifications to describe and project HIV prevalence trends across the state using annual sentinel surveillance data from 12 antenatal clinic sites spanning 2015 to 2023. The standard logistic model parameters, specifically the intrinsic growth rate, carrying capacity, and initial prevalence, are estimated by nonlinear least squares fitting using the Levenberg-Marquardt algorithm. Model fit is assessed using the coefficient of determination and root mean square error, with the logistic model achieving R-squared of 0.89 against observed prevalence data. Results indicate that HIV prevalence in the state peaked at approximately 3.8 percent in 2019 and is projected to decline to 2.6 percent by 2027 under current intervention intensity. Disaggregated analysis by age group reveals that prevalence among 25 to 34 year-olds is declining faster than among 15 to 24 year-olds, suggesting differential programme reach. Spatial mapping of clinic-level prevalence data identifies Onitsha and Awka South as areas requiring intensified targeted testing campaigns. The study recommends maintaining current ART programme intensity while addressing geographic inequities in HIV service coverage. Keywords: logistic growth model, HIV prevalence, Anambra State, sentinel surveillance, nonlinear regression.