Figure 1. Replication kinetics of mouse-adapted virus.

(A) Cells were infected with four influenza B viruses and mouse-adapted viruses at a multiplicity of infection⁵⁵ of 0.001. Cell culture supernatants were collected at 12, 24, 48, and 72 hours post infection, and viral titers were measured in units of log₁₀ TCID₅₀/mL. (B) Determination of plaque phenotype. *indicates P < 0.0001, and †indicates P < 0.001 compared with the P0 (B/Florida/04/06). The error bars show the standard errors of the mean (SEMs), which were derived from three independent experiments.