Gerhard Henrik Armauer Hansen (1841-1912) worked on leprosy throughout his career. Following his discovery of the leprosy bacillus in 1873, he proposed legislation that, when enacted in 1877 and 1885, established preventive measures aimed at isolating infectious patients. Around 1920, leprosy was more or less eradicated in Norway after a period of decline starting in 1850. Over this period, more than 8,000 cases were registered. Armauer Hansen's unique research achievement was based on a scientific and medical infrastructure in place long before he started his work. This context had several implications, though the discovery of the leprosy bacillus holds a particular fascination, with bearings on the interaction between medicine and the community even today.