Babesia is a red cell parasite endemic in the Northeastern and upper Midwestern regions of the US and responsible for the disease referred to as babesiosis. The parasite is naturally transmitted by the bite of an infected tick but may also be transmitted by blood transfusion. Infection may be asymptomatic or cause non-specific symptoms: fever, fatigue, headache, and muscle pain. In some cases, the disease can be severe, especially in those with a compromised immune system, hemoglobin-related diseases (such as sickle cell disease), and those lacking a spleen. The Red Cross began blood donation screening for Babesia microti, the species most common in the US, under an investigational protocol in June 2012 in the New England area and upper Midwest. Donors who consented to investigational screening were tested by two tests: an individual donation NAT assay (polymerase chain reaction, PCR) and an antibody assay, the latter using an indirect immunofluorescence assay (IFA). In May 2018, the Red Cross began testing whole blood samples using a NAT assay that detects the main four species of Babesia pathogenic to humans. The FDA-licensed assay that detects ribosomal RNA of the parasite following red cell lysis, significantly increased sensitivity and obviated the need for antibody testing. Because the lysis step releases thousands of Babesia-RNA copies, mini-pool testing can be performed (MPs of 16). If a reactive donation is identified, testing is repeated, and a sample is sent for antibody testing by IFA. In May 2019, the FDA released guidance to test all donations collected in the 14 states considered Babesia endemic or contiguous to an endemic state: Maine, Vermont, New Hampshire, Connecticut, Massachusetts, New York, New Jersey, Delaware, Rhode Island, Maryland, Pennsylvania, Virginia, Minnesota, and Wisconsin and in the District of Columbia. Red Cross implemented the guidance for testing in May 2020. Since then, the ARC tests about 1,600,000 donations for Babesia every year and identifies an average of 380 reactive donations. Babesia-positive donations have been identified in all 14 states, with the higher rates reported in Connecticut (1:1,581), Massachusetts (1:1,908), Maine (1:1,517), New Hampshire (1;3,944), New Jersey (1:1,2517), New York (1:3,715), and Pennsylvania (1:4,061). Reactive donors are eligible to donate again if they test NAT-nonreactive after a 2-year deferral period. Since the implementation of testing (either investigational or licensed), there have been no reported transfusion-transmitted babesia cases from tested blood. A small number of cases have been reported from states in which testing does not occur demonstrating that the range for the parasite is expanding.