title: Blood screening and unpaid donors.
mesh_terms: D001769:Blood / Q000382:microbiology*; D001782:Blood Donors; D002140:California; D005260:Female; D006515:Hepatitis B virus / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D012190:Retroviridae / Q000302:isolation & purification*