Among the momentous and disorienting changes taking place in the early nineteenth century, a stunning return of epidemic disease produced not only anxiety, but also a distrust of the industrial and imperial expansion that seemed to be responsible for its resurgence. The two most feared (although paradoxically not the most fatal) epidemic diseases, cholera and typhus, were indeed intimately related to imperial and industrial progress. Cholera was stirred out of its usual confinement in the Ganges Delta because of an increase in British troop movements in India and the increased mobility of the population made possible by railroads. Typhus, which is spread by lice, was and is a disease associated with overcrowding and poor sanitation, and was most common in the nineteenth century in the jerry-built and densely-packed housing of the great towns. The doctrine of anticontagionism, which formed the theoretical basis of the sanitary reform movement, held that these dreaded diseases were caused by filth and its odors, rather than by specific germs or particles. Because of its apparent ability to explain, predict and prevent infectious diseases, anticontagionism promised relief from the seemingly random and often deadly visitations of epidemic disease, and, equally importantly, suggested that industrial and imperial progress need not be feared because of their fatal side effects.