Gerhard Armauer Hansen (1841–1912)

Dr. Gerhard Armauer Hansen was a Norwegian physician and scientist who made a monumental breakthrough in medical history in 1873 by identifying Mycobacterium leprae, the bacterium responsible for causing leprosy (hence often referred to as Hansen's disease). His discovery proved for the first time that a chronic disease was caused by a specific microorganism rather than hereditary factors or environmental miasma, revolutionizing epidemiology and public health control measures worldwide. Marking the centenary period of his landmark discovery (Découverte du Bacille de la Lèpre), this 100-franc airmail stamp (POSTE AERIENNE) commemorates Dr. Hansen alongside microscopic depictions of the rod-shaped bacilli and a period laboratory microscope.