Methodological discussions concerning the statistical inference of R 0 are still in progress, and it is recognized that the estimate is very sensitive to dispersal (or underlying epidemiological assumptions) of the progression of a disease [7] . When one estimates R 0 using epidemic data of an emerging (or exotic) disease, the exponential growth rate, r, of infections during the initial phase of the epidemic is used [8, 9] . Assuming that the generation time, i.e., the time from infection of a primary case to infection of a secondary case generated by the primary case [10] , is known (or separately estimated from other empirical data), the growth rate r is transformed to R 0 using that knowledge (see below). That is, the conventional estimation technique has required two statistical steps, namely, first estimate r and then convert r to R 0 .