Figure 2. Seroconversion in sentinel specific-pathogen-free white leghorns after natural infection with influenza A/CK/CT/72/03 (H7N2) from overtly infected birds as quantified by hemagglutination inhibition (HI) tests for hemagglutinin (HA) antigen. The titer in HI U/mL is plotted as a function of days post overt infection of 2 birds in each group. The key is similar to that of Figure 1, except the assay is for HI. A, water only; B, water plus recombinant chicken interferon-α at 2,000 U/mL. Results of 1 trial are shown; 2 other trials gave similar results.