A simplified estimate of the effective reproduction number $$R_t$$ using its relation with the doubling time and application to Italian COVID-19 data

Abstract A simplified method to compute $$R_t$$ R t , the effective reproduction number, is presented. The method relates the value of $$R_t$$ R t to the estimation of the doubling time performed with a local exponential fit. The condition $$R_t=1$$ R t = 1 corresponds to a growth rate equal to zero or equivalently an infinite doubling time. Different assumptions on the probability distribution of the generation time are considered. A simple analytical solution is presented in case the generation time follows a gamma distribution.