FIG 3.

Pathogenicity of the WT and the variant in mice. Six mice per group were intranasally inoculated with 10⁴ TCID₅₀s/ml, 10⁵ TCID₅₀s/ml, and 10⁶ TCID₅₀s/ml (each in 50 μl) of the WT or the variant. (A) Mouse body weights were monitored daily for 14 days. The values represent the average scores of the overall body weight loss compared with the initial body weight ± standard deviations. (B) The percent survival values were calculated by observing the infected mice. (C) The mice were intranasally inoculated with 10⁵ TCID₅₀s/ml of the WT or the variant virus. Tissues were collected from the mice (n = 3) on the indicated days postinfection, and the virus titers were determined in MDCK cells. *, P < 0.01, **, P < 0.01, as determined by a t test.