FDA data (2011): out of 21 million blood components transfused, only 58 potential transfusion-related deaths were reported — a mortality risk of 1 in 362,000.

The FDA requires US hospitals to report any death suspected to be transfusion-related. In fiscal year 2011, 21 million blood components were transfused with 58 reported potentially transfusion-related fatalities (including both donors and recipients, and only suspected — not confirmed — cases). The calculated risk is 0.0000276%, or 1 in 362,000. Mike notes this data is from 2018 (the FDA report he accessed) and publicly available on the FDA website.