Fig. 1.

Replication kinetics in the upper respiratory tract of H1N1 isolates in ferrets. Groups of three ferrets were intranasally inoculated with 0.2 ml (0.l ml per nostril) of a high dose (10⁵ TCID₅₀) (A) or low dose (10² TCID₅₀) (B) of each H1N1 isolate tested. Nasal washes were collected on days 1, 3, 5, 7, and 9 after inoculation. Data are presented as mean virus titer ± standard deviation (log₁₀ TCID₅₀/ml) on the indicated day. The limit of detection was 10¹ TCID₅₀/ml.