Membrane changes associated with apoptosis in EV71-infected RD cells. Control: Uninfected RD cells. EV71: EV71-infected RD cells. The exposure of phosphatidylserine (PS) was analyzed using FITC-labeled annexin V. Cell death was assessed using PI in a time course mode. EV71-infected RD cells were harvested at 8 and 20 h postinfection and cell death was evaluated by flow cytometry.