Dynamics of RSV RNA detection in the upper and lower respiratory tract. RSV was measured in nasal wash (NW), bronchoalveolar lavage (BAL), whole lung (WL) samples from 4-14 mice per time point per group from 4 independent experiments. Mice were intranasally inoculated with 107.6-8.3 PFU in 100 μL of RSV or sterile media (non-infected controls). (A) Compared with non-infected controls, which had no RSV RNA detected at any time point, RSV RNA loads detected by real-time PCR in WL and BAL were significantly higher than RSV loads detected in NW. Values represent means (± SD) of RSV log10 RNA copies/mL. Comparisons were made by One way ANOVA; * p < 0.001. (B). By plaque assay, RSV loads were significantly higher in BAL samples compared with NW on days 1 and 5 post-inoculation. From days 1 to 5 only viral loads measured in BAL samples were higher than those assessed in non-infected controls. Values represent means (± SD) of RSV log10 PFU/mL. One way ANOVA was used for comparisons; * p < 0.05.