Randomness a key in spread of disease, other 'evil'

Working with a simple mathematical model in which chance plays a key role, researchers calculated how long it would take a bacterial infection or cancer cell to take over a network of healthy cells. The distribution of incubation times in most cases, they contend, is close to 'lognormal' -- meaning that the logarithms of the incubation periods, rather than the incubation periods themselves, are normally distributed.