Maybe someone with more background can dig on this.

Acute hemolytic transfusion reaction occurs when a patient receives the wrong blood causing a cascade of clotting in the veins. It also mentions how it can promote inflammatory cytokine release from white blood cells.

Usually accompanied by high fever and flu-like symptoms.

This sounds very familiar to Covid symptoms.

https://en.wikipedia.org/wiki/Acute_hemolytic_transfusion_reaction