Probability density functions of the incubation period and generation time of influenza. Gamma distribution was employed to model the incubation period (i.e., the time from infection to onset), whereas lognormal distribution was fitted to the generation time (i.e., the time from infection of a primary case to infection of a secondary case by the primary case). The mean and variance of the incubation period and generation time are estimated as 1.43 days and 0.48 days2 and 2.92 days and 5.57 days2, respectively. For the original data see:  and .
Nishiura et al. BMC Infectious Diseases 2009 9:27 doi:10.1186/1471-2334-9-27