If case no one has mentioned, modern detergents have surfactants that strip off stained or bound stuff from the fabric, and proteases (enzymes) that can break apart proteins into peptides. If some retard did have HIV and stained his shirt, provided that he and YOU both used detergent that isn't $1/US barrel or sold from some guy in a white van chances are most of the viruses in the bloodstain will be destroyed - viruses usually have proteins as coating.
