Figure 3

Frequency distribution of the cycle threshold (Ct) values from all positive samples and all different tissue combinations tested with RT-qPCR for ISAV (listed in Additional file 1: Table S1). The yellow bar corresponds to frequency distribution of average Ct values of 66 official ISAV-HPR0 positive farm sites. The red bar corresponds to frequency distribution of four 2013 ISAV-HPR∆ cases.