In this work, we investigate a modified population model of non-infected and infected (SI) compartmentsto predict the spread of the infectious disease COVID-19 in Pakistan. For Approximate solution, we use LaplaceAdomian Decomposition Method (LADM). With the help of the said technique, we develop an algorithmto compute series type solution to the proposed problem. We compute few terms approximate solutionscorresponding to different compartment. With the help of MATLAB, we also plot our approximate solutionsfor different compartment graphically.