Hansen's discovery of the leprosy bacillus

Norway was probably the country in Europe worst hit by leprosy in the mid-19th century. In the 1850s about 2 people in every 1,000 had the disease nationally, and as many as 25 per 1,000 in Bergen, which had several leprosy hospitals. The leading authority, Daniel Cornelius Danielssen of the Lungegaard Hospital in Bergen, held with most of his colleagues that leprosy was hereditary.

Gerhard Armauer Hansen (1841 to 1912), a native of Bergen, went to work under Danielssen in 1868 and learned the newest histological methods in Bonn and Vienna. He studied skin, mucous membranes and nerves from leprosy patients. On a February evening in 1873 at the Lungegaard Hospital he saw rod-shaped bodies in the tissue under his microscope. In every leprous nodule he removed from a living patient, he later wrote, small staff-like bodies much like bacteria lay inside many of the cells. He proposed that they caused the disease, and published in Norwegian in 1874 and in English in 1875.

Proof was hard to come by. The bacillus could not be grown in culture, and Hansen could not transmit it to animals. He tried to inoculate the eye of a woman with material from a leprosy patient without her consent, and in 1880 a court found him guilty and he lost his post as resident physician at the Bergen leprosy hospital. That year the German bacteriologist Albert Neisser, who had taken tissue preparations from Hansen in 1879 and stained them more successfully, published the organism as his own discovery. A leprosy conference in Berlin in 1897 recognized Hansen as the discoverer.

Hansen became chief physician for leprosy in Norway in 1875 and proposed the laws of 1877 and 1885 that provided for isolating patients. Norway counted 1,800 people with leprosy in 1875, 575 in 1901 and 160 in 1920.