comparison of different approaches in estimating initial reproduction number of sars-cov-2 in the islamic republic of iran

Background: the basic reproduction number (r0) is an epidemic threshold parameter that indicates the magnitude of disease transmission and thus allows suggestions for the planning of control measures. objectives: our aim in this study was to compare different approaches for estimating r0 in the early stage of the sars-cov-2 outbreak and discern the best-fitting model. methods: the dataset was derived from cumulative laboratory-confirmed covid-19 cases from 26th february to 30th may 2020 in iran. the methods of exponential growth (eg) rate, maximum likelihood (ml), time-dependent (td) reproduction number, attack rate (ar), and sequential bayesian (sb) model were used. the gamma distribution (mean 4.41±3.17 days) was used for serial interval (si) distribution. the best-fitting method was selected according to the lowest root mean square error (rmse). results: we obtained the following estimated r0 [95% confidence interval]: 1.55 [1.54; 1.55], 1.46 [1.45; 1.46], 1.31 [1.30; 1.32], and 1.40 [1.39; 1.41] using eg, ml, td, and sb methods, respectively. additionally, the eg and ml methods showed an overestimation of r0, and the sb method showed to be under-fitting in the estimation of r0. the ar method estimated r0 equal to one. the td method had the lowest rmse. conclusions: the simulated and actual r0 of td showed that this method had a good fit for actual data and the lowest rmse. therefore, the td method is the most appropriate method with the best performance in estimating actual r0 values.