This section is from the book "The Home Hand-Book of Domestic Hygiene and Rational Medicine. Volume 2.", by J. H. Kellogg, M.D.. Also available from Amazon: The Home Hand-Book of Domestic Hygiene and Rational Medicine, Volume 2.
Small-pox is undoubtedly the result of infection of the system by a specific germ, the origin of which is still wrapped in mystery. Although it is known that the disease has existed for many centuries, it is not known how it originated, or what country is its native home. Experience with the disease has shown that bad food, uncleanly and unhygienic habits, intemperance, dissipation of all sorts, unsanitary conditions, and the crowding together of large numbers of people, greatly facilitate the propagation of the disease and increase its fatality.
During the last two decades of the last century the mortality from this disease constituted one-twelfth of the total mortality in Berlin. During the same century the mortality from small-pox amounted to 30,000 persons annually. During the seventeenth and eighteenth centuries the deaths from this disease in England amounted to one-eleventh of the total mortality. According to the eminent Dr. Curschmann, of Berlin,from whose exhaustive article in Ziemssens Cyclopedia of Medicine we cull these facts, small-pox came to be dreaded more than the plague. The disease continued its ravages notwithstanding the most earnest efforts of the most eminent physicians to stay its progress. It even penetrated to the jungles of Africa and the wilds of North and South America, where it carried off whole tribes of savages.