RSV A2, BT2a, BT3a and BT4a one step and multistep growth curves. PBEC monolayers from 5 individual donors were infected with RSV A2, BT2a, BT3a and BT4a at MOIs of 0.1 (A) or 5 (B). Cells were scraped into the medium and harvested every 24 h post infection. Virus growth kinetics were determined by titrating virus in each sample. The data are presented as mean ± S.E. log10 TCID50/ml. Areas under the curve were calculated and compared using a student's paired t-test. *P < 0.05. **P < 0.01. ***P < 0.001.