 Blood transfusion was formerly the second @-@ most common mode of transmission for Chagas disease , but the development and implementation of blood bank screening tests has dramatically reduced this risk in the 21st century . Blood donations in all endemic Latin American countries undergo Chagas screening , and testing is expanding in countries , such as France , Spain and the United States , that have significant or growing populations of immigrants from endemic areas . In Spain , donors are evaluated with a <unk> to identify individuals at risk of Chagas exposure for screening tests . 
