Disease Transmission

Even though blood components are tested rigorously for certain infectious diseases, bacterial, viral, parasitic, and prion pathogens continue to evolve. If they are not detected, they can cause harm to the patient and even death. Donors must be screened to determine eligibility. Their blood samples are also tested for hepatitis B and C, human immunodeficiency virus (HIV) 1 and 2, human T-cell lymphotropic virus (HTLV) I and II, West Nile virus, and syphilis. The table to the right describes the screening tests performed on all blood donors in the United States.

It is not yet possible to eliminate the risk of infectious disease transmission through transfusions. There are many other organisms that may be transmitted through transfused blood, which are not routinely tested for in the blood supply. These organisms include the Epstein-Barr virus, cytomegalovirus (CMV), bacteria, and parasites such as malaria, Babesia microti, and Trypanosoma cruzi, which is responsible for Chagas disease, and prions such as variant Creutzfeldt-Jakob disease (vCJD).

The selection of eligible donors is critical to ensuring the blood supply's safety. Donors with certain lifestyles, medical conditions, travel histories, immigration backgrounds, or specific physical findings are deferred for a specific period or indefinitely. This minimizes the risk that a transmittable agent will be present in the donor's blood.