A Fractional-Order Mathematical Model for Infectious-Disease Transmission and Control: Stability, Sensitivity and Numerical Analysis
I. O. Okpara *
Department of Mathematics, University of Abuja, Abuja, Nigeria.
S. A. Kambai
Department of Mathematics, University of Abuja, Abuja, Nigeria.
V. C. Obinna
National Open University of Nigeria, Abuja, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Infectious-disease dynamics may retain effects associated with previous exposure, delayed behavioural responses, and earlier interventions. This study formulates a six-compartment susceptible–exposed– symptomatic–asymptomatic–hospitalised–recovered model governed by a Caputo derivative of order 0 < \(\alpha\) \(\le\) 1. Vaccination, treatment, and public awareness are represented through distinct mechanisms: removal of susceptible individuals, accelerated removal of symptomatic infectious individuals, and reduction of effective transmission, respectively. The analysis establishes positivity, boundedness, and local well-posedness; derives the disease-free and endemic equilibria; and obtains the controlled reproduction number using the nextgeneration matrix. The disease-free equilibrium is locally asymptotically stable when R0 < 1 and unstable when R0 > 1, while a stronger sufficient condition is provided for global disease elimination. The reproduction number is decomposed into symptomatic and asymptomatic contributions, clarifying the distinct roles of the two infectious pathways. Normalised sensitivity indices identify transmission and asymptomatic infectiousness as factors that increase R0, whereas vaccination, treatment, recovery, hospitalisation, and awareness reduce the threshold. Reproducible predictor–corrector simulations show that the fractional order affects transient epidemic timing and peak behaviour, while combined interventions can move the illustrative system across the R0 = 1 threshold. Because all numerical parameters are illustrative rather than estimated from a specific outbreak, the numerical findings should be interpreted as mechanistic demonstrations rather than disease-specific forecasts or empirical intervention-effect estimates.
Keywords: Caputo derivative, fractional-order model, infectious-disease transmission, memory effect, reproduction number, asymptomatic transmission, stability analysis, sensitivity analysis, vaccination, treatment, public awareness, predictor–corrector method