Simulating the transmission dynamics and control of typhoid fever in Ibadan, Nigeria

This study aims to assess transmission dynamics of typhoid and simulate effects of treatment, isolation and vaccination in reducing the burden of typhoid fever in Ibadan metropolis, Nigeria. Secondary data of the Integrated Disease Surveillance Response on reported typhoid fever cases for 2010 to 2017 period in Ibadan South-East Local Government Area, Oyo State, Nigeria were used to achieve the set-out objectives. The study adapted the Susceptible-Infected-Carrier-Recovered (SIIcR) model to simulate effects of the three preventive and control strategies on typhoid fever transmission. Typhoid fever cases were most rampant among the age groups 20 to 40 years (29.0% infected) and > 40 years (35% asymptomatic carriers and 45.0% death) and the least in age group 0 to 28 days (0.22% infected and no death case). A decreasing trend in typhoid fever cases (56 cases per year) was observed which was attributed to improved functional health facilities and their effective utilization. Significant seasonal variation in typhoid infections was found with the highest reported cases at the start of wet (April) and dry (November) seasons. The SIIcR model simulations suggested likelihood of typhoid fever epidemic within two weeks in the community if no prevention and intervention measures were put in place. Major reduction in the carriers’ population significantly reduced the number of infected class and suggested disease-free population within a season of typhoid epidemic (100 days). Model simulations suggested that vaccination and isolation significantly reduced the effect of infected and asymptomatic carrier populations at p<0.05 on the transmission dynamics of typhoid fever.