The Dynamic Effective Reproductive Number of COVID-19 during the Epidemic in Iran

We aimed to determine the generation time, the best model for estimating reproduction number (R), and to estimate the basic reproduction number (R0) and effective reproduction number (Rt) for COVID-19 in Iran.

We used the daily incidence cases of COVID-19, hospitalized due to a probable diagnosis of COVID-19 from 19 February 2020 to 17 November 2020 in Iran. Four models, including maximum likelihood (ML), exponential growth (EG), time-dependent (TD), sequential Bayesian (SB) were evaluated. The weekly reproduction number with a 95% confidence interval (CI) was calculated.

TD model shows the best fit compared to other models for estimating reproduction number in Iran. The R0 in Iran in the first week of the epidemic, leading up to 21 February 2020 was 7.19, 95% CI: 5.56, 9.00.  The lowest value for the Rt was equal to 0.77 between 3 to 10 March 2020 and 4 to 11 December 2020. From 11 June 2020 up to13 August 2020, the Rt was more than one but after then to 24 September 2021 was less than one.

TD model was the best fit for estimating the R in Iran. The worst situation of the epidemic in Iran was related to the weeks leading up to 26 February 2020 and 28 October 2020, and better status was related to the weeks leading up to 10 March 2020 and 11 December 2020.