Figure 4. Antibody response to the H5N3 virus in ducks (top) or in chickens (bottom).

Antibody titers were measured by ELISA (left) or HI method (right) from serum collected at the indicated time in days (d) after primary infection (H5 groups, black bars) or secondary infection (H5H5 groups, white bars) and were expressed as the reciprocal of the dilution of serum used for measurement as indicated in the Materials and Methods section. Significant differences between groups are indicated with asterisks (*, P<0.05; **: P<0.01; ***: P<0.001).