Viral detection in pharyngeal and cloacal swabs using RT-PCR and virus isolation. Bar graph with standard error estimates of results of viral detection in pharyngeal and cloacal swabs taken from gulls inoculated on day 0 with HPAIV H5N1 virus and followed for 12 days. (A) Real-time RT-PCR, expressed as 40 (minimum cycling threshold [Ct] value considered negative) - actual Ct value. (B) Virus isolation, expressed as 10x × median tissue culture infectious dose per mL (TCID50/mL), with a titre < 100.8 TCID50/mL considered negative. Numbers below each day (in parentheses) represent total number of birds tested on that day. Each bar represents the average value for all birds tested on that day.