Armauer Hansen. Portrait of Norwegian bacterio- logist Armauer Gerhard Henrik Hansen (1841-1912), researcher of leprosy. He studied medicine at the University of Christiana (now Oslo), graduating in 1866. In 1868, Hansen began work at the Bergen leprosy hospital. At the time leprosy was thought to be inherited, but Hansen concluded that it was an infectious disease. He observed rod-shaped bacilli bacteria in specimen tissues; the bacteria we now know as Mycobacterium leprae. Hansen said this was the cause of leprosy, but in his research he could never transmit the disease. By isolating patient’s, however, he successfully reduced the incidence of leprosy in Norway.