HA surface expression of A/HK/218847/06 (H1N1) and A/HK/218449/06 (H3N2) influenza viruses. MDCK cells were infected with either virus at m.o.i. = 1. HAs were stained with anti-HA mAb and Alexa488-coupled goat anti-mouse Abs (green). The nuclei were counterstained with TO-PRO-3 (blue). The HA surface expression was analyzed at indicated time points by confocal laser scanning microscopy. The merger of both channels is shown.