Mathematical analysis of Lassa fever epidemic with effects of environmental transmission

Lassa fever (LF) is a viral hemorrhagic fever transmitted predominantly by rodents vector. It is a deadly disease that is endemic in some west African countries. In this paper, we adopt a deterministic epidemic model of susceptible-exposed-infectious-removed (SEIR)-type to study the dynamics of the LF transmission. The model involves environmental contamination and isolation of infected individuals. The result elucidates the effect of direct and indirect pathogenicity on LF disease. Qualitative analysis of the model reveals the existence of backward bifurcation (BB). This phenomenon entails the co-existence between a stable disease-free equilibrium (DFE) and endemic equilibrium (EE) even if the reproduction number, R-0, is below unity which makes the control of LF more strenuous and depends on the magnitude of the initial sub-populations. We fitted the model to the reported cases in Nigeria from 4 January to 4 October 2020. We observed that the model captures well the epidemic patterns of the LF dynamics in Nigeria, which is essential in designing effective control and mitigation strategies. Finally, using the partial rank correlation coefficient (PRCC), the outcome of a sensitivity analysis suggests the most sensitive epidemiological parameters to reduce or mitigate the Lassa virus spread in Nigeria and beyond.