Estimation of the basic reproduction number (R0) of the COVID-19 epidemic in Iran

Abstract

Background: Estimation of the basic reproduction number of an infectious disease is an important issue for controlling the infection. Here, we aimed to estimate the basic reproduction number (R0) of COVID-19 in Iran. Methods: To estimate R0 in Iran and Tehran, the capital, we used 3 different methods: exponential growth rate, maximum likelihood, and Bayesian time-dependent. Daily number of confirmed cases and serial intervals with a mean of 4.27 days and a standard deviation of 3.44 days with gamma distribution were used. Sensitivity analysis was performed to show the importance of generation time in estimating R0. Results: The epidemic was in its exponential growth 11 days after the beginning of the epidemic (Feb 19, 2020) with doubling time of 1.74 (CI: 1.58-1.93) days in Iran and 1.83 (CI: 1.39-2.71) in Tehran. Nationwide, the value of R0 from February 19 to 29 using exponential growth method, maximum likelihood, and Bayesian time-dependent methods was 4.70 (95 CI: 4.23�5.23), 3.90 (95 CI: 3.47�4.36), and 3.23 (95 CI: 2.94�3.51), respectively. In addition, in Tehran, R0 was 5.14 (95 CI: 4.15�6.37), 4.20 (95 CI: 3.38�5.14), and 3.94 (95 CI: 3.45�4.40) for exponential growth, maximum likelihood, and Bayesian time-dependent methods, respectively. Bayesian time dependent methods usually provide less biased estimates. The results of sensitivity analyses demonstrated that changes in the mean generation time affect estimates of R0. Conclusion: The estimate of R0 for the COVID-19 ranged from 3.94 to 5.14 in Tehran and from 3.23 to 4.70 in nationwide using different methods, which were significantly larger than 1, indicating the potential of COVID-19 to cause an outbreak. This work has been published under CC BY-NC-SA 1.0 license. Copyright © 2020. Iran University of Medical Sciences