Figure 1. Clinical indices, mortality, and viral shedding of naive mute swans after inoculation with A/Cygnus cygnus/Germany/R65/2006 highly pathogenic influenza virus subtype H5N1. A) All animals were observed daily for up to 21 days for clinical signs and classified as healthy (0), ill (1), severely ill (2), or dead (3). A clinical index was calculated that represents the mean value of all naive swans per group for this period. B) Percentage survival of swans expressed as mean value of all naive swans per group. C and D) Mean values of the shedding of infectious virus of both groups (high dose = 106 50% egg infectious dose [EID50]/animal, and low dose = 104 EID50/animal) of naive mute swans are shown. Mean cycle threshold (Ct) values of real-time reverse transcription–PCR (RT-PCR) analyses of tracheal and cloacal swabs are depicted for both groups. Standard deviations are shown as error bars. TCID50, 50% tissue culture infectious dose.