Guidance on the Management of Asymptomatic Blood Donors Who Test Positive for Babesia

Background: Regional blood donor screening for Babesia has been conducted in the United States since 2019, using highly sensitive and specific nucleic acid testing (NAT). Currently, there are no recommendations regarding the management of asymptomatic blood donors who test positive for Babesia. Methods: A multidisciplinary expert panel was convened to develop guidance for the management of asymptomatic Babesia-infected blood donors. Additionally, a survey was distributed through the Infectious Diseases Society of America (IDSA) Emerging Infections Network (EIN) to evaluate how a geographically diverse group of infectious diseases specialists would approach this problem. Results: The expert panel recommends that all Babesia NAT-positive blood donors should be referred for clinical evaluation and retesting using peripheral blood smear (PBS) and Babesia PCR. The panel also recommends observation rather than treatment for a reactive molecular test alone. Antimicrobial therapy should be considered for PBS-positive cases. Donors should be instructed to seek medical care if symptoms develop. The EIN survey results are consistent with these recommendations. Conclusions: Since blood donors comprise healthy, immunocompetent adults, findings of incidental Babesia infections in asymptomatic donors are frequently self-limited. Longitudinal studies show that molecular evidence of infection in blood donors clears in almost all without intervention.