FIG. 2.

Kinetics of survival rate after inoculation with 1 (A) or 10 (B) μl of a PR8 solution containing various doses into each nostril. Mice were inoculated with 1 μl of a PR8 solution into each nostril for infection of the upper respiratory tract (A) and with 10 μl of a PR8 solution into each nostril for infection of the lower respiratory tract (B). Virus dose group symbols: ⧫, 10^1.5 EID₅₀ of PR8 (n = 6); ○, 10^2.5 EID₅₀ of PR8 (n = 6); ●, 10^3.5 EID₅₀ of PR8 (n = 6); ▵, 10^4.5 EID₅₀ of PR8 (n = 6); ▴, 10^5.5 EID₅₀ of PR8 (n = 6).