Numerous viral pathogens can be transmitted through blood. Most of the viruses, in fact, spreads in the host organism transported from the bloodstream (viremia) to reach its target organ. The degree of transfusion safety guaranteed by the combined action of the clinical-anamnestic selection of voluntary donors, periodicals and unpaid, and the serological methods and genome amplification for screeening of communicable infections is very high at this time.
The risk of transmission by transfusion therapy of hepatitis B virus infections, hepatitis C and HIV has gradually decreased over the past decades thanks to the introduction of numerous preventive strategies. The window phase, that is, the temporal gap that goes from the moment of infection to the moment of seroconversion, during which an infected donor can have a high viremia in the absence of signs and / or symptoms of infection, in fact, it has been greatly reduced from combined action of the measures mentioned above.