One of the characteristic signs of infectious diseases, signs that allowed medical thought long before the discovery of the kingdom of microbes to single out infectious diseases into a special, peculiar group of diseases, is the fact that these diseases become widespread from time to time when we talk about the presence of an epidemic. The repeated observation that one sporadic case is often followed by mass diseases, just as from one thrown spark a huge fire spreads over a vast territory, made it possible for scientific thinkers of ancient times to say that the cause of infectious diseases is something that capable of development and reproduction, or, more simply, must be a living being. This truth, as everyone is well aware, has become a scientific property only since the time of the brilliant works of Pasteur and Koshʹa, whose name is associated with the emergence of medical microbiology as an independent scientific discipline of medical knowledge. The brilliant discoveries of the pioneers of medical microbiology brought extraordinary inspiration to the mood of those who were busy with the idea of penetrating deeper into the mysterious phenomena surrounding the question of the nature of infectious diseases. Since then, the study of infectious diseases, which has made in a very short period of time a number of extremely important discoveries of both theoretical and practical nature, has been concentrated mainly in the laboratory, largely obscuring the methods of clinical and epidemiological analysis of phenomena for a short time. The enthusiasm for the successes of experimental bacteriology was so great that it seemed to many that the mere fact of the discovery of the causative agent of the disease was enough to consider the question of this infection almost settled. The persistent pursuit of the discovery of new pathogenic microbes was largely fueled by a one-sided idea of the role of a pathogenic agent in the emergence and development of a disease: the presence of specific bacteria was considered the only necessary and completely sufficient condition for the origin of infectious diseases. Soon, however, when the first frenzy of discovery dissipated, when our knowledge of infection and pathogens increased significantly, we, says Muller, became much more humble. Where it seemed to us that we clearly see all the details, many new tasks arose: many clinical data, which during the first bacteriological enthusiasm were almost handed over to the archives, came into their own again, and, recognizing the extraordinary progress to which we owe to the discoveries of Koshʹa and his disciples, we must nevertheless admit that we are still very far from the goal that we considered already achieved." Both from the data of experimental bacteriology and from everyday observation of the occurrence of infectious diseases, it became clear that, in addition to the absolutely necessary presence of a pathogenic microbe, other conditions must also be met for an infectious disease to develop. These conditions, first of all, must be sought in the properties of the infected organism, and therefore we must consider infectious diseases as a biological phenomenon, which is a function of the interaction of two living beings on each other. And since the properties of a macro- and microorganism do not represent a constant value, but change sharply depending on external conditions, in the final analysis, when studying infectious diseases, we must reckon with 3 factors: 1) the totality of the properties of a macroorganism, 2) the properties of a pathogenic microbe and 3) a set of external conditions under which the influence of both creatures on each other occurs. These three main lines determine the ways of studying infectious diseases, and for the success of a comprehensive knowledge of these diseases, all these lines of direction turn out to be equally valuable and necessary. These provisions, however, do not determine the immediate tasks facing medical thought in the study of infections. The individual tasks of this vast branch of medical knowledge turn out to be very different depending on the goal that the researcher sets for himself, as well as depending on the approach to such a complex biological phenomenon as infectious diseases. The clinic predominantly has in mind the goal of practical servicing of a diseased organism in terms of treatment, diagnosis, proper care, etc. infection, to study the protective forces of the macroorganism, which it has in the fight against infection, the mechanism of recovery and immunity, in other words, to study the intimate picture of the combat between the macro and the microorganism.
Riding the Shi: From Infection Barriers to the Microbial City