Figure 6. Evaluation of H1 virus transmission in ferrets. Donor ferrets (black lines; n = 2 ferrets/group) were inoculated with 106 50% tissue culture infectious dose (TCID50) units of H1 influenza virus sw/Chile (A), Mem/87 (B), or sw/IA (C) viruses. Naive ferrets (n = 2) were either placed in the same cage with the infected group (direct contact, blue lines) or housed in separate cages (respiratory transmission, red lines) and nasal washes were collected on the indicated day postinfection for virus quantification by TCID50 analysis. Lines represent individual animals. Dashed line represents limit of detection of the assay.