Replication of H7N7/ 03 viruses in the upper and lower respiratory tract of ferrets. A) Ferrets were i.n. inoculated with 107.4 TCID50 of virus and nasal washes collected at 1, 3, 5, 7 and 9 days p.i. were titrated in MDCK cells. Mean virus titers (n=4) are shown with error bars indicating standard deviations. The dotted line indicates the lower limit of detection. B) Mean virus titers in nasal turbinate (NT), trachea and lung tissues collected from ferrets (n=3) on day 5 p.i. Error bars represent the standard deviations.