Comparison of RSV loads measured by PCR in lung supernatants of BALB/c and C57BL/6 mice. Groups of 2–12 BALB/c (△) and C57BL/6 (●) mice per group per time point were inoculated intranasally with sterile 10% EMEM (control), and were compared with RSV A2 infected Balb/c (□) and C57Bl/6 (◆) mice. Viral load was determined by PCR to detect RSV N gene. Data are presented as mean ± SEM Log10 PFU/ml of BAL. p < .05, by t-test when data normally distributed, or by Mann-Whitney Rank sum test when data were not normally distributed.