Nine-month Trend of Time-Varying Reproduction Numbers of COVID-19 in West of Iran

Background: the basic reproduction number (r0) is an important concept in infectious diseaseepidemiology and the most important parameter to determine the transmissibility of a pathogen.this study aimed to estimate the nine-month trend of time-varying r of covid-19 epidemic usingthe serial interval (si) and markov chain monte carlo in lorestan, west of iran.study design: descriptive study.methods: this study was conducted based on a cross-sectional method. the si distribution wasextracted from data and log-normal, weibull, and gamma models were fitted. the estimation oftime-varying r0, a likelihood-based model was applied, which uses pairs of cases to estimaterelative likelihood.results: in this study, rt was estimated for si 7-day and 14-day time-lapses from 27 february-14november 2020. to check the robustness of the r0 estimations, sensitivity analysis was performedusing different si distributions to estimate the reproduction number in 7-day and 14-day timelapses.the r0 ranged from 0.56 to 4.97 and 0.76 to 2.47 for 7-day and 14-day time-lapses. thedoubling time was estimated to be 75.51 days (95% ci: 70.41, 81.41).conclusions: low r0 of covid-19 in some periods in lorestan, west of iran, could be an indicationof preventive interventions, namely quarantine and isolation. to control the spread of the disease,the reproduction number should be reduced by decreasing the transmission and contact rates andshortening the infectious period.