Pathogen inactivation: A process designed to eliminate pathogens from water, air or donated blood. Pathogens include viruses, bacteria, and fungi. Sewage purification systems depend upon pathogen inactivation to purify water to the extent it may be safe enough to drink. Air purification systems may incorporate a HEPA filter to cleanse the air of germs. Pathogen inactivation in blood targets DNA or RNA of pathogens while ignoring components used in transfusions. The components in transfusions, red blood cells, platelets, and plasma, do not contain genetic material, therefore are unharmed.