To measure viral shedding, each day each ferret was swabbed in the nasal, throat and fecal passages and the viral titer was measured by TCID 50 ( Table 2 ). The highest levels of viral shedding were measured in the throat swabs. Nasal swabs also showed viral shedding for most animals, while the presence of virus in rectal swabs was low although detectable in a few animals. Replication of H1N1pdm in nasal turbinates and lungs were determined post-mortem from the right caudal lobe of the lung taken on euthanasia (Table 3) . Four sections were taken per lobe to provide greater insight into the spread of the virus in the tissue (Fig. 4) . High levels of virus were detected in all nasal turbinate samples at 1, 2, and 3 DPI (95% C.I. = 5.43+/21.00 TCID 50 / mL). Virus was also detected in a majority of lung sections from 1, 2, and 3 DPI. It was absent in the lung sections from one animal on 2 DPI, although it was present in the ferret's nasal turbinates, suggesting that the timing of infection in this animal was slower than the others. Of note, this same animal had a focus of consolidation on CT and radiotracer uptake on PET. This observation also suggests that, while the virus may have been undetectable by TCID 50 , low levels of virus had entered the lower respiratory system. No animals on day 7 post-infection had detectable virus in the nasal turbinates or the sampled lung tissue. Virus was not detected in nasal, throat and fecal passages or the sampled lung tissue from ferrets in any of the controls.