Waterborne Infections

WATERBORNE INFECTIONS. The significance of water in the spread of infectious diseases was noted even in ancient times. Already Hippocrates recommended using boiled or aromatic water to protect against infection. Since then, for centuries, medicine did not lose sight of the role that contaminated water could play in epidemic outbreaks. However, at that time, it was considered sufficient to explain the origin of an epidemic by any banal, non-specific contamination of water, soil, air, food products, etc. The first considerations regarding the specific nature of contamination were expressed in 1849 by Snow, who observed a cholera epidemic in London. Snow asserted that for the spread of cholera, it is necessary that the excretions of patients contain the cholera contagion and that this contagion enters the intestines of new people, which occurs either through direct contact with the sick or through drinking water contaminated with cholera excretions. Similar conclusions were reached somewhat later, in 1856-1873, by Budd, based on the study of typhoid fever epidemics. Budd asserted: "To cause typhoid fever, typhoid fever is needed." According to Budd, specific infection can occur through the transmission of infection either by direct contact of the sick with the healthy or through air and water contaminated with the contagion. "Leaving the sick intestine in liquid form," says Budd, "the infectious matter infects the soil, from which, passing through soil filters, it can reach water reservoirs used for drinking." Hence Budd's requirements for careful sanitary supervision of the purity of drinking water sources. Budd's ideas at the time formed the basis of sanitary legislation in England and in many cases gave brilliant results in the anti-epidemic measures of that country. Budd's theory of the water origin of epidemics encountered in Germany the "telluric" theory of Pettenkofer, who had numerous followers and taught that the infectious principle excreted by a sick person becomes contagious to other people only after maturing in the soil. In France, the water theory of the origin of epidemics was also received with considerable skepticism. Most French epidemiologists associated the occurrence and spread of epidemics with putrefactive emanations from cesspools, poorly maintained wells, etc. The question of the epidemiological role of water was finally clarified only when Pasteur proved through bacteriological research the presence in water of a large number of various microbes, among which he often found those pathogenic to humans, and finally, when Koch in 1884 found the cholera vibrio in water reservoirs (in India). In 1587, Brouardel in France confirmed this fact for the typhoid bacillus. Subsequently, it was established that water may contain: the dysentery microbe (Pfuhl), the tetanus bacillus (Roux and Vaillard), the anthrax bacillus (Diatroptov) and other microbes of epidemic diseases. Among the microbes found in water, epidemiologists distinguish 2 main groups: 1) saprophytic microbes, which do not play a direct role in the occurrence of infections, and 2) parasitic microbes, pathogenic to humans and animals. Bacteriological analysis of water of various origins shows that in some of them saprophytes of the most diverse kinds (such as, for example, cocci, bacteria that liquefy gelatin, yeasts, molds, etc.) reach innumerable quantities. Some of them, in association with pathogenic microbes, can enhance the poisonous effects of the latter. Such conditional significance also have bacteria whose presence in water indicates contamination with fecal matter, such as putrefactive microbes and some bacterial species that usually lead a saprophytic existence but are capable of occasionally showing pathogenic action. These include: the group of B. coH, Proteus vulgaris, Proteus mirabilis, Bacterium clioa, Bac. fluorescens liquefaciens, Bac. violaceus, Bac. jacintheus, Bac. fluorescens putrificus, Bac. pyocyaneus, Bac. faeca-lis alkaligenes, Staphyloccccus albus, Entero-coccus and others. However, water becomes especially threatening from an epidemiological point of view only when it is a carrier of microbes capable of causing an epidemic outbreak. Among such microbes, the cholera vibrio, typhoid fever bacteria, paratyphoids A and B, dysentery, as well as apparently the causative agents of epidemic infectious jaundice and dysentery amebas, are primarily included. From an epidemiological point of view, it is important to know the properties of water that affect the duration of life in it of pathogenic species of microbes. Here, first place is given to: the chemical composition of water, the degree of its aeration, the effect of light on it, temperature, etc. The chemical composition of water, the degree of its aeration, the effect of light on it, temperature, etc. also have a significant influence on the duration of life in water of a pathogenic species. The saprophytic microbial flora characteristic of a given water source also has a significant influence on the duration of life in water of a pathogenic species, because among this flora there may be saprophytes that compete antagonistically with the pathogenic species. Finally, as old observations by Hankin on the effect of the water of the Ganges River on the cholera vibrio and modern research by Twort, d'Herelle and others show, some water sources may have the ability to quickly destroy pathogenic microbes, giving with them the phenomenon of the so-called bacteriophagy (see). All the above-mentioned moments so complicate the question of the average duration of life of pathogenic microbes in water that the numerical data available to epidemiology on this question must be considered as conditional, requiring individual verification in each particular case, and these numerical data are derived from test-tube experiments and, of course, cannot give correct ideas about the duration of life of pathogenic microbes in natural conditions, when they are subjected to diverse, mobile and difficult to account for influences on them of this or that water source. In ice, some pathogenic microbes in a state of anabiosis can remain viable for whole months, for example, the typhoid bacillus for over 3 months, the cholera vibrio for over 4 months. Such resistance to low temperatures can explain the overwintering of many-year cholera epidemics. Repeated freezing and thawing quickly kills both the typhoid bacillus and the cholera vibrio. The distinctive features of waterborne epidemics are as follows: 1) the unusually, catastrophically rapid development of the epidemic; 2) simultaneous infection of numerous population groups in direct contact with the contaminated water source, with almost complete well-being of the other groups not using the contaminated source; 3) rapid decline of the epidemic from the moment of discovery of the contaminated water source and cessation of its use by the population. The extent of a waterborne epidemic in each individual case is determined by the importance for the population of the contaminated water source. If a public water source is contaminated, then the epidemic wave covers the entire population. If individual springs, wells, pools are contaminated, then the outbreak is limited only to those, sometimes small, population groups that use this contaminated source. A characteristic feature of a waterborne epidemic is its curve, which in pure cases has a steep rise and almost as rapid a fall. In a contact epidemic, however, when the carrier of infection is the patient himself, new victims are drawn into the epidemic wave only slowly, as they come into contact with the patient. Therefore, the distinctive epidemiological feature of a contact outbreak will be a curve that rises slowly and sluggishly and declines just as sluggishly. However, history knows of almost no pure waterborne epidemics. This is understandable if one takes into account that every patient (whether he was infected from a water source or by contact from a previous patient) is himself capable of spreading infection by contact. Thus, to every waterborne epidemic, cases of its contact spread are inevitably added. This is expressed in the fact that after the steep decline of the wave of a waterborne epidemic, there remains still a long period of slowly fading contact outbreak. Such periods are usually called the contact "tail" of the waterborne epidemic. On the other hand, sometimes the curve of a waterborne epidemic is superimposed on the curve of a contact epidemic or endemicity. On the curves presented here (see figures 1 and 2), one can easily see all these combinations of waterborne epidemics with contact ones. Epidemic measures for the protection of public water sources are divided into two groups: 1) measures that protect water sources from contamination with pathogenic microbes, and 2) measures that seek to sanitize already contaminated sources.

The effectiveness of the measures of both the first and second groups must be controlled by constant sanitary supervision and daily bacteriological and sanitary-hygienic analysis of water from the respective sources to determine their cleanliness and safety. The measures of the first group are purely preventive in nature and consist of proper technical equipment and capture of drinking water sources and the organization of so-called protection zones for water supply sources. The measures of the second group become significant only in the case of water sources being contaminated with pathogenic microbes. These measures include: 1. The earliest possible detection of infection in water sources and their immediate closure for public use. 2. In cases where the contaminated water source is the only drinking source for a given populated area, it is necessary to identify and eliminate the causes of its contamination. The population must be immediately informed of the danger to which they are exposed when using raw water, urgent and persistent propaganda must be conducted on the necessity of boiling this water, and measures must be taken to supply the population with boiled water (boilers), at least in places of public use (stations, piers, lodging houses, etc.). In relation to the contaminated source itself, a series of sanitary measures for its cleaning, including chlorination disinfection (see Chlorination), is applied, and intensified sanitary-bacteriological control over this source is conducted. 3. In cases where certain groups of the population, for example, military units, due to the nature of their activities must change their location and are therefore exposed to the danger of infection from unknown water sources, they are supplied with mobile disinfection installations and individual water filters for drinking water. 4. The use of water sources in which pathogenic microbes have been found is permitted again only after double bacteriological examination confirms both times in succession that they are free from infection, and only after they have been technically protected from new contamination. 5. Under no conditions are bacillus carriers (see Bacillus carriage) permitted to work at water supply and water treatment facilities. 6. Constant sanitary control over water supply is necessary on the basis of relevant laws and regulations.