 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 questionnaire to identify individuals at risk of Chagas exposure for screening tests . 
 Blood transfusion was formerly the second @-@ most common mode of transmission for Chagas disease , but the development and implementation of blood bank screening tests <a href='been_done' title='1'><mark>has</mark></a> 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 , <a href='null_relcl' title='2'><mark>that</mark></a><a href='got' title='3'><mark>have</mark></a> significant or growing populations of immigrants from endemic areas . In Spain , donors are evaluated with a questionnaire to identify individuals at risk of Chagas exposure for screening tests . 
Blood transfusion was formerly da second @-@ most common mode of transmission for Chagas disease , but tdadevelopment and implementation of blood bank screening tests done dramatically reduced this risk in the 21st century . Blood donations in alll endemic Latin American countries undergo Chagas screening , and testing is expanding in countries , such as France , Spain and thdanited States , got significant or growing populations of immigrants from endemic areas . In Spain , donors are evaluated with a questionnaire to identify individuals at risk of Chagas exposure for screening tests .