Viruses and Koch's Postulates

Abstract

Diseases at one time were thought to be caused by wrath of gods, configuration of stars or miasmas. After a real struggle that occurred not so many years ago, certain maladies were shown to be induced either by small animals or minute plants, e.g., protozoa, fungi, bacteria and spirochetes. Indeed, victory was so great that most workers in time began to consider that all infectious diseases, including those whose incitants had not been discovered, must be caused by agents similar to those already recognized. According to them, there could be no infections that were not caused by protozoa, fungi, bacteria or spirochetes, and to intimate that some infectious agents might be inanimate constituted heresy of first order. Even at present time, cause of certain diseases is said by some individuals to be unknown or undiscovered, because no cultivable bacterium or visible protozoan parasite of etiological significance has been demonstrated in them. For instance, a few years ago Cowie made statement in a scientific paper that etiological agent of poliomyelitis is unknown, and in recent book, An American Doctor's Odyssey, Heiser remarked that the microbe which causes smallpox has never been discovered. In spite of general acceptance of idea that all infectious diseases are caused by protozoa, fungi, bacteria or spirochetes, some workers have always contended that there might exist other infectious agents incapable of classification with those already known. Furthermore, very early in bacteriological era a few discerning individuals appreciated fact that there was no reason, except analogy, for assuming that all infectious agents must be living autonomous organisms. Through activities