On Tuesday an alliance of companies and aid groups announced plans to test experimental drugs and collect blood plasma from Ebola survivors to treat new victims of the disease in West Africa. Plasma from survivors contains antibodies that the immune system makes to fight the virus. Several Ebola patients have received survivor plasma and recovered, but doctors say there is no way to know whether it really helps without a study like the one they are about to start within a month. To date there are no drugs or vaccines approved for Ebola. Doctors Without Borders said last week it would host studies of experimental treatments and plasma at three of its West Africa treatment centres.