An international consortium led by the Institute of Tropical Medicine in Antwerp, meanwhile, announced it would study whether treating Ebola patients with antibodies from the blood of survivors could help. WHO experts said international travelers from the three hardest-hit nations — Guinea, Sierra Leone and Liberia — should still be screened for possible Ebola symptoms to prevent the disease from spreading further. In Spain, five of the 15 people who came into contact with a nursing assistant who survived Ebola were released from the hospital Thursday after spending 21 days under observation and showing no signs of the disease.