Serological status, as determined by hemagglutination inhibition, of wood ducks (<i>Aix sponsa</i>) 21 days after experimental pre-exposure to low pathogenicity avian influenza (LPAI) viruses<sup>a</sup>, and 10 days after challenge with the highly pathogenic avian influenza (HPAI) virus A/whooper swan/Mongolia/244/05 (H5N1)<sup>b</sup>.

a<p>Birds were inoculated via choanal cleft with a dose of 10<sup>6</sup>EID<sub>50</sub> of different LPAI viruses. Serologic data of the naïve group were omitted due the 100% mortality observed in this group, and data of the A/mallard/Netherlands/2/05 (H5N2) group were omitted due to lack of seroconversion.</p>b<p>Birds were challenged via choanal cleft with a dose of 10<sup>4</sup>EID<sub>50</sub> of A/whooper swan/Mongolia/244/05 (H5N1), 21 days after experimental pre-exposure to different subtypes of LPAI viruses.</p>c<p>Samples with HI titer≥8 were considered positive.</p>d<p>HI using antigen against homosubtypic LPAI virus, either H1N1, H5N1, or H5N2.</p>e<p>HI using antigen against A/whooper swan/Mongolia/244/05 (H5N1).</p>f<p>Abbreviations: LPAIV-dpe = days after LPAI pre-exposure; HPAIV-dpc = days after H5N1 HPAI challenge; † = succumbed to HPAI H5N1 infection.</p>