In 1873, Gerhard-Henrik Armauer Hansen published his report that claimed leprosy to be an infectious disease with a description of the infectious material in leprous tissue.

Hansen had discovered Mycobacterium leprae as the causative organism for leprosy, defying the hereditary affliction theory of the disease.

It was estimated in the 1850s that roughly two individuals per thousand in Norway were afflicted with leprosy, and as much as 25 per thousand in his hometown in Bergen. It was to his credit that Bergen became the epicenter of leprosy research.