The estimation of R 0 is achieved by measuring the exponential growth rate r from the incidence data and also by assuming that g() is known (or separately estimated from empirical observation such as contact tracing data [12, 13] ). It should be noted that the above mentioned framework has not been given a likelihood-based method for estimating R 0 (i.e., a likelihood function used for fitting a statistical model to data, and providing estimates for R 0 , has been missing). Moreover, equation (5) may not be easily used by non-experts, e.g., an epidemiologist who wishes to estimate R 0 using her/his own data.