Transfusion-Transmitted Babesia microti.

Because testing of donors for Babesia microti has become available, it is important to determine the kinds of patients who should receive B microti-tested blood. We searched PubMed, AABB abstracts, and FDA Web site to identify all cases of transfusion-transmitted babesiosis (TTB). Cases were analyzed for underlying medical condition, age, presence of spleen, and reason for transfusion in relation to 5 classes of recipient outcome severity. Sixty-seven reports included 256 transfusion cases where donor tested positive for B microti, 165 of which resulted in TTB. Sixty recipients did not develop disease or become test positive, and test results were not known for 31 more. The 165 cases of TTB involved hematologic (19%), neonate (10%), cardiovascular (8%), and gastrointestinal (6%) patients. Thirty-two (19%) of the 165 infected patients died with death attributed to babesiosis in 25 of the cases. Nine (5%) were asymptomatic, 27 (16%) were symptomatic but had uncomplicated disease, and 16 (10%) had complicated disease. The severity of disease was mixed among many disease categories. Patients >65 years of age included the largest number of recipients (59/165, 36%) and deaths (11/32, 34%), although deaths occurred in other age groups as well. TTB cases were predominantly due to red cells (133 of 140 specified units), with red blood cell units processed in a variety of ways and at all storage duration. TTB with complicated babesiosis and/or death occurred in patients of all age groups and with a variety of underlying medical conditions.