If you want to be really technical the survivors would also lose 50% of all the other cells in their bodies and probably wouldn't live another few months. I'm not a doctor so I won't try to put a number of weeks, days or hours on it, let alone argue that number, but hey knock yourself out.
/edit based on another comment - even if you could stay physically intact with half the cells in your body dying, half of your brain cells dying would probably kill you instantly.