The delay in the peak of viral titer between the two strains is qualitatively consistent with the model predictions of the previous section: the H275Y mutant strain appears to have a longer latent infection period than the WT strain. To make this comparison more quantitative, we scaled each experimental data set such that the peak virus was equal to one and then performed a least-squares fit to the full set of normalized data for each virus strain ( Figure 7B ). We utilized a model similar to that used for the analysis of the multiple-cycle viral yield assay, but allowed for a normal distribution of the latent infection period among cells rather than a fixed value for all cells, as assumed previously (see Materials and Methods). The fitted value of the average latent infection period, t L , was found to be 5.6 h for the WT strain and 7.5 h for the H275Y mutant, with fitted values of the standard deviation in the normal distribution, s L , of 0.5 h and 1.2 h, respectively. These results are summarized in Table 2 , along with 95% confidence intervals determined by fitting 1000 bootstrap replicates [46] .