Modelling the Spread of Waterborne Diseases Using Stochastic Epidemic Models in Jos, Plateau State

Recurrent cholera and typhoid fever outbreaks in Jos, Plateau State, North Central Nigeria, reflect the combined effects of inadequate water treatment infrastructure, poor sanitation coverage, and climate variability that creates seasonal disease transmission conditions. This study develops stochastic compartmental epidemic models to simulate the dynamics of waterborne disease spread in Jos metropolis and evaluate the effectiveness of public health intervention strategies. An SIWR (Susceptible-Infected-Waterborne pathogen-Recovered) model is formulated as a continuous-time Markov chain, incorporating environmental pathogen concentration as an explicit disease driver alongside direct person-to-person transmission. Model parameters are calibrated using weekly cholera case notification data from the Plateau State Ministry of Health spanning five years. Gillespie's stochastic simulation algorithm is implemented to generate ensemble trajectories of outbreak dynamics under baseline and intervention scenarios. Intervention strategies evaluated include chlorinated water supply expansion, sanitation infrastructure improvement, oral cholera vaccination campaigns, and combined multi-component programmes. Results indicate that water chlorination expansion offers the greatest cost-effectiveness ratio among single interventions, reducing expected outbreak size by 67 percent at N280 million in annual infrastructure investment. Combined interventions achieve near-elimination conditions under sustained implementation. Stochastic model results reveal important probability distributions for outbreak size and duration that deterministic models obscure. Recommendations include prioritizing chlorination infrastructure and establishing real-time cholera surveillance. Keywords: stochastic epidemic model, waterborne disease, cholera, Jos, public health intervention