FIG 3.

Human IAVs achieve higher peak titers relative to swine and canine IAVs but comparable total viral loads. A total of 12 guinea pigs were inoculated intranasally with each dose of virus. The mean with standard error is shown, with n = 1 to 12, as some animals were not productively infected. (A) Viral titers at the time of peak shedding. Data from doses of 1 × 10¹, 1 × 10², and 1 × 10³ PFU were compared across groups using a two-way ANOVA with Tukey’s correction for multiple comparisons to evaluate significance. NL/09 and Pan/99 were not significantly different at any dose. sw/Sp/04 and sw/KS/07 were not significantly different at any dose. * indicates significant difference relative to NL/09 (P < 0.01); # indicates significant difference relative to Pan/99 (P < 0.01). (B) All doses tested were analyzed by linear regression. Slopes were significantly nonzero only for NL/09 and can/IL/15 viruses (P < 0.05). (C) The area under the curve was calculated for each animal individually to quantify total virus shed into nasal washes over the time course. Two-way ANOVA with Tukey’s correction for multiple comparisons revealed no significant difference among virus strains. (D) Relationship between inoculation dose and area under the curve. Curve fits use a quadratic model.