Comparisons of viral growth in vitro. A Viral growth assay. CCB cells were infected with the strains indicated (see top of the figure for the symbol code used) and the log10 value of the titer (pfu/mL) in the cell supernatant was determined at the indicated dpi. Data are presented as the mean + SEM (standard error of the mean) of triplicate measurements. B Viral plaque assay. CCB cells were infected with the strains indicated, and plaques areas were measured over time. Data presented are the mean + SEM for measurements of 20 randomly selected plaques. C Correlation between plaque size measured at 10 dpi (B) and viral titers measured at 4 dpi (A). Data presented are the mean ± SEM.