The WHO has stated that transfusion of whole blood or purified serum from Ebola survivors has the greatest potential to be implemented immediately, and has issued an interim guideline for this therapy.[41] A study in Sierra Leone started in November 2014, and preliminary results show an 80 percent survival rate.[42] Trials in Liberia and Guinea started in January 2015, with funding from the Gates Foundation.[43] Blood transfusions were also used in a 1995 outbreak in the Democratic Republic of the Congo, and 7 out of 8 patients survived.[44]