is the mean age at infection, and G~1 mzs z 1 mzc is the ecological generation length of the infection. Figure 1a is a plot of the data for the outbreak from 2007 through 2009. To estimate model parameters and determine the critical level of control needed to eradicate the epidemic, the model described by the equations in (7) is fit to the data collected during the Kitgum outbreak ( Figure 1 ) During the invasion phase of HEV, the prevalence is approximately