Influenza viral RNA load in nasal swabs. Quantification of influenza RNA was performed by RT-qPCR at the indicated days PI. Bars indicate average values of positive samples in genome equivalent copies (GEC) of plasmid per swab in group SwH1N1/Mock (A), Mock/pH1N1 (B) and SwH1N1/pH1N1 (C). The number of positive samples from the total number of animals was indicated above each bar. Samples from animals in group Mock/Mock were all below the limit of detection, which is indicated by the dotted line. Error bars represent one SD above and below the mean.