Assessing approximation of time to observe epidemic peak. A. Comparison of epidemic curves in the absence of intervention between explicit numerical and approximate solutions. The population size is assumed to be 100,000 with initial condition (S0, I0, U0) = (99998, 1, 1). The generation time is exponentially distributed with mean 1/γ = 3 days. B. Comparison of estimated delay in epidemic peak (imposed by a short-lasting intervention) between explicit numerical and approximate solutions. The assumed length of intervention t1 is 50 days.