The condition for microassay experiments was chosen at a virus MOI of 5 and 24 h,based on the following results.Released viruses were detected at 6 h postinfection and peaked at 36 h postinfection. So,24 h time point represented the active stage of infection with increased viral titer. At this time point,we postulated that cell state would largely represent the steady gene expression changes. In addition, when HUVECs were infected with H9N2 viruses at a MOI of 5, we could obtain a good replication kinetic pattern of the viruses.