Figure 5

Relationship between viral RNA load and AIV antibody levels for ducks and seabirds. Each point represents an individual and colours indicate infection status. A Data from all ducks (n = 76) from Figure 4 are included in this plot, along with data for 100 seabirds (42 Atlantic puffins, 16 black-legged kittiwakes, 28 common murres, and 14 northern gannets). Individuals were classified as being currently infected, recently infected, or naïve/waned, using the same classification as in Figure 4. An arrow denotes the expected immunological response shown by the seventeen currently infected individuals, illustrating the relationship between increasing antibody levels with decreasing viral RNA load. These same individuals are shown in B, where a generalized linear model (GLM) was fit to show the relationship between antibody level and viral RNA load, with the gray area indicating the 95% confidence interval of the model. The vertical lines at an S/N ratio of 0.5 represent the threshold value used to classify seropositivity, with lines at 0.7 also shown as the threshold occasionally used for this assay in other studies.