About 20-25% of individuals infected with SARS-CoV-2 develop severe symptoms, but many infected individuals are asymptomatic and may donate blood without knowledge of infection or before they become symptomatic. In several previous studies, SARS-CoV-2 RNA has been detected in blood donors, but transfusion transmission has not been documented. In order to investigate further if asymptomatic or pre-symptomatic blood donors positive for SARS-CoV-2 are infectious, researchers in France asked blood donors to report symptoms related to COVID-19 or positive test results. Between January 20 and May 29, three of 268 (1.1%) donations screened tested positive for SARS-CoV-2 RNA. The first of the three SARS-CoV-2 RNA-positive donors remained asymptomatic. Before post-donation viral test results were reported for this donor, however, pathogen-reduced plasma was transfused to a recipient who remained asymptomatic and red blood cells were transfused to a patient who already had COVID-19. Blood products from the two other positive donations were not transfused to patients. Despite concentrating viral particles in all three plasma samples, cell culture experiments did not demonstrate viral infectivity. Further research and hemovigilance is needed in order to determine the SARS-CoV-2 RNA levels needed for viral transmission of this respiratory virus in blood.
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