Coronavirus disease (COVID-19,) a novel coronavirus originated from Wuhan, a city in the Hubei Province of China at the end of 2019, has further progressed rapidly to become a global epidemic. In February 2020, the World Health Organization (WHO) designated the disease as COVID-19 and declared it as a global pandemic, as the disease has spread to nearly all the continents and the cases are rising at an exponential rate.A confirmed case of COVID-19 infection is defined as those with a positive result for viral infection and history of acute respiratory illness for the collected specimens. A suspected case is defined as a patient with symptoms of COVID-19 infection, but not confirmed by viral nucleic acid testing. An actual estimate of the serial interval was considered by estimating the time from onset of illness in a primary case (infector) to illness onset in a secondary case (infected) in a transmission chain. Serial interval can only be estimated by linking dates of onset for infector-infected data pairs, and these links are difficult to be established. R0 is defined as the actual expected number of secondary cases that one primary case will generate in a susceptible population
