=+63. Once an individual has been infected with a certain disease, let x represent the time (days) that elapses before the individual becomes infectious.

The article “The Probability of Containment for Multitype Branching Process Models for Emerging Epidemics” (J. of Applied Probability, 2011:

173–188) proposes a Weibull distribution with  5 2.2 and  5 1.1 for x 2 .5 (i.e. the Weibull density curve is shifted to the right of 0 by .5; Minitab refers to .5 as the value of the threshold parameter).