Before revision:  Here, using a simple mathematical model , we quantify the downstream impact of a contagion that mutates exactly once as it travels . Assuming that this mutation occurs at a random node in the contact network, we calculate the distribution of the number of "descendants," d, downstream from the initial "Patient Zero" mutant.
After revision:  Here, using a simple susceptible-infected (SI) model of contagion, we explore the downstream impact of a contagion that mutates exactly once as it travels . Assuming that this mutation occurs at a random node in the contact network, we calculate the distribution of the number of "descendants," d, downstream from the initial "Patient Zero" mutant.