We estimated the reproduction number, R, using a simple method that relies on the estimation of the growth rate, ''r,'' by fitting an exponential function to the early ascending phase of the epidemic curves in Lima and the rest of Peru [5, 23, 26, 27] . The early ascending phase was determined as the period between the day of pandemic onset (as defined earlier) and the midpoint between the onset and peak days. The reproduction number was calculated by substituting the estimate for r into an expression derived from the linearization of the classical Susceptible-Exposed-Infectious-Recovered (SEIR) transmission model [26, 28] :