Hansen Identifies the Cause of Leprosy

In 1873, Norwegian physician Gerhard Henrik Armauer Hansen examined diseased tissue under a newly acquired microscope in Bergen and identified small rod-shaped bodies inside the cells of leprosy patients. At the time, prevailing European medical opinion considered leprosy to be an inherited constitutional ailment or the consequence of atmospheric miasmas. Hansen's observation of what is now designated as Mycobacterium leprae provided early tangible physical evidence that the disfiguring chronic condition was caused by a specific transmissible infectious agent rather than hereditary degeneration.

Hansen had completed his medical degree with honors in 1866 at the University of Christiania, later known as the University of Oslo. Following brief positions at Rikshospitalet in the capital and as a physician serving communities in Lofoten, he returned to his birth city of Bergen in 1868. There, he took a post at Lungegard Hospital under the supervision of Daniel Cornelius Danielssen, a leading authority on leprosy who staunchly defended the view that the illness was passed down through family bloodlines.