# Popular Science Monthly/Volume 62/February 1903/Preventive Medicine

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* PREVENTIVE MEDICINE.
By General GEORGE M. STERNBERG, U.S.A..
FROM the earliest times physicians have taken the lead in all that relates to the prevention of disease. In times of epidemic their advice is sought by afflicted communities and they have been instrumental in securing most of the legislation which has been enacted with a view to preventing or restricting the prevalence of infectious diseases. As members of boards of health, they are largely responsible for the enactment and execution of proper sanitary legislation, and as medical officers of the Army and Navy, they are charged with the duty of guarding the health of soldiers and sailors enlisted in the service of their country.
While the principal function of a physician engaged in civil practice is to give proper advice and treatment to the sick, he is constantly called upon to point out the most effectual methods of preventing the extension of infectious diseases in the homes of his patients; to indicate the proper diet and mode of life to be followed by convalescents and other members of families which he regularly attends, etc. All this he does cheerfully, although he rarely receives any compensation for advice of this kind and his professional income is diminished in direct proportion to his success in the prevention of disease among the families constituting his clientele.
The compensation for voluntary work in public or domestic sanitation is to be found in the consciousness of good accomplished and of high and humane motives worthy of the profession to which we belong, and the willingness to perform such voluntary service is one of the most noteworthy distinctions between the educated and honorable physician and the ignorant and mercenary quacks who prey upon the community with no other object in view than that of gain. The beneficent results of preventive medicine are seen in the greatly reduced mortality rates in civilized countries generally, and especially in the fact that certain pestilential maladies which formerly prevailed as wide-spread and devastating epidemics, causing the death of hundreds of thousands of human beings annually, have to a great extent lost their deadly potency as a result of the progress of our knowledge with reference to their etiology and the best methods of combating them. ​Smallpox no longer claims its victims in any considerable numbers except in communities where vaccination is neglected; cholera has been excluded from our country during the last two widespread epidemics in Europe and its ravages have been greatly restricted in all civilized countries into which it has been introduced; the deadly plague of the seventeenth and eighteenth centuries is no longer known in Europe and the prevalence of typhus so—called spotted or 'ship fever'—has been greatly limited. Typhoid fever, tuberculosis and diphtheria are still with us and claim many victims, but we know the specific cause of each of these diseases; we know where to find the bacteria that cause them and the channels by which they gain access to the human body; and we know how to destroy them by disinfecting agents.
The mortality from tuberculosis is constantly diminishing in our large cities and the complete destruction of the infectious sputa of those suffering from pulmonary tuberculosis would no doubt go a long way towards the extermination of this fatal disease.
Perhaps the triumphs of preventive medicine can not be better illustrated than by a brief historical account of the prevalence of bubonic plague during the past three or four centuries. It can scarcely be doubted that the 'black death' of the fourteenth century was the same disease which subsequently prevailed in Europe under the name of 'the plague'—now more generally spoken of as 'bubonic plague.' While modern methods of diagnosis have enabled us to recognize typhoid fever, typhus fever, relapsing fever and bubonic plague as distinct diseases, it must be remembered that up to the end of the fifteenth century no such differentiation had been made and the term 'pest' was applied to any fatal malady which prevailed as an epidemic, and no doubt in some instances included smallpox, which prior to the discovery of Jenner contributed largely to the general mortality of the population of Europe.
Bubonic plague continued to prevail in various parts of Europe at the end of the sixteenth century, and early in the seventeenth century (1603) an epidemic occurred in London which caused the death of 38,000 of its inhabitants. It continued to prevail in this city and in various parts of England, Holland and Germany and six years later caused a mortality of 11,785 in the city of London. During the year 1603 a most disastrous epidemic occurred in Egypt, which is said to have caused a mortality of at least a million. After an interval of ten or fifteen years, during which there was a marked diminution in the number of cases and the extent of its distribution in European countries, it again obtained wide prevalence during the year 1620 and subsequently, especially in Germany, Holland and England. The epidemic in the city of London in 1625 caused a mortality of more than 35,000. In 1630 a severe epidemic occurred in Milan, and in 1636 London ​again suffered a mortality of over 10,000, while the disease continued to claim numerous victims in other parts of England and on the continent. Later in the century (1656) some of the Italian cities suffered devastating epidemics. The mortality in the city of Naples was in the neighborhood of 300,000, in Genoa 60,000, in Rome 14,000. The smaller mortality in the last-named city has been ascribed to the sanitary measures instituted by Cardinal Gastaldi. Up to this time prayers, processionals, the firing of cannons, etc., had been the chief reliance for the arrest of pestilence, with what success is shown by the brief historical review thus far presented. But this enlightened prelate inaugurated a method of combating the plague and other infectious maladies which, with increasing knowledge and experience in the use of scientific preventive measures, has given us the mastery of these pestilential diseases, and has been the principal factor in the extinction of bubonic plague from the civilized countries of Europe.
But it was long after the time of Cardinal Gastaldi before sanitary science was established upon a scientific basis and had acquired the confidence of the educated classes. Indeed, the golden age of preventive medicine has but recently had its dawn, and sanitarians at the present day often encounter great difficulty in convincing legislators and the public generally of the importance of the measures which have been proved to be adequate, when properly carried out, for the prevention of this and other infectious maladies.
We have now arrived in our review at the period of the 'great plague cf London.' For some years this city had been almost if not entirely free from the scourge, but in the spring of 1665 it again appeared and within a few months caused a mortality of 68,596 in a population estimated at 460,000. This, however, does not fairly represent the percentage of mortality among those exposed, for a large proportion of the population flew from the city to escape infection.
Upon the continent the disease prevailed extensively, especially in Austria, Hungary and Germany. The epidemic in Vienna in 1679 caused a mortality of 76,000. In 1681 the city of Prague lost 83,000 of its inhabitants. During the last quarter of this century the disease disappeared from some of the principal countries of Europe. According to Hirsch it disappeared from England in 1679, from France in 1668, from Holland about the same time, from Germany in 1683 and from Spain in 1681. In Italy it continued to prevail to some extent until the end of the century.
At the beginning of the eighteenth century bubonic plague prevailed in Constantinople and at various points along the Danube; from here it extended in 1704 to Poland, and soon after to Silesia, Lithuania, Germany and the Scandinavian countries. The mortality in Stockholm ​was about 40,000. The disease also extended westward from Constantinople through Austria and Bohemia.
In 1720 Marseilles suffered a severe epidemic, probably as a result of the introduction of cases on a ship from Leghorn. The mortality was estimated as being between 40,000 and 60,000. From Marseilles as a center it spread through the province of Provence, but did not invade other parts of France. In 1743 a severe outbreak occurred on the island of Sicily. A destructive but brief epidemic, which is estimated to have caused a mortality of 300,000, occurred during the years 1770 and 1771 in Moldavia, Wallachia, Transylvania, Hungary and Poland. At the same time the disease prevailed in Russia, and in 1771 caused the death of about one fourth of the population of the city of Moscow.
Early in the nineteenth century (1802) bubonic plague appeared at Constantinople and in Armenia. It had previously prevailed in the Caucasus, from which province it extended into Russia. In 1808 to 1813 it extended from Constantinople to Odessa, to Smyrna and to various localities in Transylvania. It also prevailed about the same time in Bosnia and Dalmatia. In 1812 to 1814 it prevailed in Egypt, and, as usual, was conveyed from there to European countries. During the same year it prevailed extensively in Moldavia, Wallachia, and Bessarabia. In 1831 it again prevailed as an epidemic in Constantinople and various parts of Roumelia, and again it appeared in Dalmatia in 1840 and in Constantinople in 1841. Egypt, which for centuries had been the principal focus from which plague had been introduced into Europe, continued to suffer from the disease until 1845 when it disappeared from that country.
The last appearance of oriental plague in Europe, until its recent introduction into Portugal, was the outbreak on the banks of the Volga in 1878-79. The disease had previously prevailed in a mild form in the vicinity of Astrakhan and was probably introduced from that locality. An interesting fact in connection with this epidemic is that in Astrakhan the disease was so mild that no deaths occurred, and that the earlier cases on the right bank of the Volga were-of the same mild form, but that the disease there increased rapidly in severity and soon became so malignant that scarcely any of those attacked recovered. This is to some extent the history of epidemics elsewhere, and not only of plague, but of other infectious diseases, such as typhus fever, cholera and yellow fever. In all of these diseases the outset of an epidemic may be characterized by cases so mild in character that they are not recognized, and during the progress of the epidemic many such cases may continue to occur. These cases are evidently especially dangerous as regards the propagation of the disease, for when they are not recognized no restrictions are placed upon the infected individuals, although they may be sowing the germs broadcast.
​The termination of an epidemic in the pre-sanitary period depended to a considerable extent upon the fact that those who suffered a mild attack acquired thereby an immunity; and that when the more susceptible individuals in a community had succumbed to the prevailing disease there was a necessary termination of the epidemic for want of material.
Another factor which no doubt has an important bearing upon the termination of epidemics is a change in the virulence of the germ as a result of various natural agencies. Time will not permit me to discuss this subject in its scientific and practical aspects, but the general fact may be stated that all known disease germs may vary greatly in their pathogenic virulence, and that in every infectious disease mild cases may occur, not only because of the slight susceptibility of the individual, but also because of the 'attenuated' virulence of the specific germ. In the eighteenth century, the beginning of sanitary science, isolation of the sick and seaboard quarantines came to the aid of these natural agencies, and did much in the way of arresting the progress of this pestilential disease. At the present day these measures, together with disinfection by heat or chemical agents, are relied upon by sanitarians with great confidence as being entirely adequate for the exclusion of this disease or for stamping it out if it should effect a lodgment in localities where an enlightened public sentiment permits the thorough execution of these preventive measures; but when the disease prevails among an ignorant population which strenuously objects to the carrying out of these measures, the contest between the sanitary officer and the deadly germ is an unequal one, and the stamping out of an epidemic becomes a task of great magnitude, if not entirely hopeless. This is illustrated by the experience of the English in their encounter with bubonic plague in their Indian Empire.
Plague seemed to be almost a thing of the past and no longer gave any uneasiness in the countries of Europe which had formerly suffered from its ravages, when in February, 1894, it made its appearance in the city of Canton-) China, and three months later in Hong Kong. The disease is known to have been epidemic in the province of Yunnan, which is about 900 miles distant from Canton, since the year 1873, but it attracted little attention until the lives of Europeans living in the city of Hong Kong were threatened by the outbreak of an epidemic among the Chinese residents of that place. Many thousands of deaths occurred in Canton during the three months which elapsed after its introduction to that city before it effected a lodgment in Hong Kong.
Fortunately this outbreak gave the opportunity for competent bacteriologists to make scientific investigations relating to the specific cause of this scourge of the human race and to the demonstration that it is due to a minute bacillus. This discovery was first made by the ​Japanese bacteriologist, Kitasato, who had received his training in the laboratory of the famous Professor Robert Koch, of Berlin. This discovery was made in the month of June, 1894, in one of the hospitals established by the English officials in Hong Kong. About the same time the discovery was made, independently, by the French bacteriologist, Yersin. From this time the study of the plague has been established upon a scientific basis and very material additions have been made to our knowledge with reference to the prevention and 'treatment of the disease.
That the plague bacillus has not lost any of its original virulence is amply demonstrated by the high death-rate among those attacked, and we are justified in ascribing its restricted prevalence to the general improvement in sanitary conditions in civilized countries and to the well-directed efforts of public health officers in the various localities to which it has been introduced during recent years. In the Philippine Islands, where it prevailed to a considerable extent when our troops first took possession of the City of Manila and where the conditions among the natives are extremely favorable for its extension, it has been kept within reasonable bounds and, indeed, the latest reports indicate that it has been practically exterminated by the persistent efforts of the medical officers of our army, charged with the duty of protecting the public health in those Islands.
The monthly report of the Board of Health for the city of Manila for September, 1902, the last at hand, records but one death from plague during that month. During the same period there were ten deaths from typhoid fever, thirty-five deaths from dysentery and seventy-six deaths from 'the great white plague,' pulmonary tuberculosis.
Bubonic plague, cholera and typhoid fever have long been classed as 'filth diseases,' and in a certain sense this is correct, although we now know that the germs of these diseases not only are not generated by filth, but do not multiply in accumulations of filth. They are present, however, in the alvine discharges of the sick, and when this kind of filth is exposed in the vicinity of human habitations or gains access to wells or streams, the water of which is used for drinking, the germs are likely to be conveyed to the alimentary canals of susceptible individuals, and thus the disease is propagated. Until quite recently the attention of sanitarians was so firmly fixed upon the demonstrated transmission of cholera and typhoid fever through the agency of contaminated water or milk that certain other modes of transmission were overlooked, or at least underrated. I refer to the transmission by insects, or as dust by currents of air. I have for many years insisted upon the part played by flies as carriers of infectious material from moist masses of excreta from cases of cholera and typhoid fever. There ​is good reason to believe that the bacillus of bubonic plague may be transmitted in the same way. The cholera spirillum is quickly killed by desiccation and this disease is probably very rarely, if ever, communicated through the medium of dust. But the germs of typhoid fever and of bubonic plague are more resistant and, without doubt, under certain circumstances, these diseases are extensively propagated by means of dust containing desiccated excreta. There is a good reason to believe that in several of our camps, during the Spanish-American War, this was an important factor in the etiology of typhoid fever epidemics. The average mortality from typhoid fever in our regular army since the Civil War has been, for the first decade (1868-1877) 95 per 100,000 of mean strength; for the second decade (1878-1887) 108 per 100,000, for the third decade (1888-97) 55 per 100,000. This latter rate compares favorably with that of many of our principal cities; for example, it is exceeded by the typhoid death-rate of the city of Washington, which is 78.1 per 100,000 (average of 10 years, 18881897), by that of the city of Chicago, which is 64.4 per 100,000; by that of Pittsburgh, which is 88 per 100,000. As a result of insanitary conditions existing in the camps in which our troops were hastily assembled at the outset of the Spanish-American War, the typhoid death-rate in our army of volunteers and regulars during the year ending April 30, 1899, was more than 22 times as great as it had been in our regular army during the decade immediately preceding the war period. As compared with the Civil War, however, there was a decided improvement, the typhoid mortality for the first year of the Civil War having been 1,971 per 100,000 of mean strength and for the Spanish-American War 1,237 per 100,000.
Experience shows that new levies of troops are especially subject to typhoid fever and other infectious 'camp diseases,' not only because of lack of discipline and consequent difficulty in the enforcement of sanitary regulations, but also because the individual soldiers are very susceptible to infection, owing to their age, the abrupt change in their mode of life, the exposure and fatigue incident to camp life, and last, but not least, their own imprudence as regards eating, drinking, exercise, etc. In the absence of sewers or other adequate means of removing excreta, the camp site is likely to become infected by the discharges of unrecognized cases of typhoid and typhoid bacilli are carried by flies to the kitchens and mess-tents and deposited upon food, or as dust are directly deposited upon the mucous membranes of the respiratory passages of those living in the infected camp. That preventive medicine has still serious work before it is shown by the fact that according to the last census return there were 35,379 deaths from typhoid fever in the United States during the census year 1900. The increase in mortality over the number in 1890 (27,056) is out of proportion to the ​increase in population, notwithstanding the general improvement in the sanitary condition of towns and cities. This is no doubt due to the continued pollution of water supplies and to the extension of this infectious disease in rural districts. It is in fact now an endemic disease in nearly all parts of the United States.
According to the census report of 1900, there were 111,000 deaths from tuberculosis during the year 1900. This does not, however, include the deaths in certain states in which the vital statistics are incomplete or unreliable, and it is probable that there are at least 145,000 victims of the great white plague annually within the limits of the United States. The last census return in those states where registration was approximately correct, including a population of about 21,000,000 people, shows that 12 per cent, of all deaths resulted from pulmonary tuberculosis, 8.5 per cent, from pneumonia, 3 per cent, from typhoid fever and 3 per cent, from diphtheria and croup. These figures indicate to some extent the task which preventive medicine has still to accomplish.
A most interesting and notable example of the beneficent results following the practical application of sanitary measures based upon exact knowledge relating to the etiology of an infectious disease is afforded by the recent extinction of yellow fever in the city of Havana, which for many years had been the principal focus of infection in the West Indies, and the port from which it has been repeatedly carried to the seaport cities of the United States. According to the reports of the health officers in that city, there has not been a case of yellow fever in Havana for more than a year, and the extinction of the disease is ascribed entirely to the vigorous measures enforced to prevent its transmission by mosquitoes of the species proved by the researches of Reed and Carroll to be the immediate hosts of the yellow fever parasite and the active agents in the transmission of the disease from man to man. During the first sixty years of the past century, yellow fever prevailed almost annually in one or more of the southern seaports of the United States and not infrequently it extended its ravages to the interior towns in one or more of the southern states. So frequently did it prevail during the summer months in New Orleans and Charleston that the permanent residents of those cities commonly regarded it as a disease of the climate and a necessary evil which it was folly to attempt to combat by quarantine restrictions.
In the great epidemic of 1853, yellow fever prevailed extensively in the states of Florida, Alabama, Louisiana, Mississippi, Arkansas and Texas. The epidemic of 1867 was limited to the states of Louisiana and Texas. Those states again suffered severely in 1873 and the states of Florida, Alabama and Mississippi were also invaded. A still more extended and deadly epidemic occurred in 1878, causing a mortality ​of 15,934 out of a total number of cases exceeding 74,000. In this epidemic the disease followed the Mississippi River to the very suburbs of St. Louis, and the state of Tennessee suffered severely as well as the states south of it. The city of Memphis alone had a mortality from the disease of about 5,000. These repeated epidemics not only cost the lives of thousands of citizens and paralyzed business of all kinds during their prevalence, but apprehension with reference to the recurrence of the disease very materially interfered with the growth of many southern cities and retarded greatly the development of those portions of the country most liable to invasion. All this is now changed; public health officials are no longer filled with apprehension upon the approach of summer by the thought that any ship arriving from Havana may introduce the deadly pestilence to our shores; commerce is no longer subjected to the serious restrictions formerly considered necessary for the exclusion of the disease; and the public generally have been made aware that the fangs of this threatening monster have been drawn by the scientific demonstration of its mode of attack and the simple measures which have been proved to be effective in preventing its propagation. Until the recent demonstration of the transmission of yellow fever by mosquitoes, this disease was generally regarded as one of the filth diseases, although there were many facts opposed to this view. In the light of our present knowledge we can no longer class it with typhoid fever, cholera, bubonic plague and dysentery, in which diseases the germ is known to be present in the alvine discharges of the sick and which are, consequently, well named filth diseases.
We now see clearly, however, why in certain particulars relating to its etiology it resembles the malarial fevers. It is limited as regards its prevalence to comparatively warm latitudes or to the summer months in more temperate regions and is dependent, to a certain extent, upon rainfall or the proximity of standing water, because these conditions are necessary for the propagation of mosquitoes. As regards the filth diseases, properly so-called, no single agency is more important for their prevention than the use of properly constructed sewers for the reception of excreta and its removal from the vicinity of human habitations. Sewers had come into use and had the warm endorsement of sanitarians long before the discovery of the germs of the infectious maladies under discussion, and before it was positively known that the infectious agent in these diseases is contained in the discharges from the bowels. But now that we have an exact knowledge of the etiology of these diseases, the reason for the beneficent results attending the use of sewers, in connection with an ample and pure water supply, is apparent. It may be safely asserted that a city or town having a complete and satisfactory sewer system and a pure water supply is practically immune from epidemics of cholera or typhoid ​fever, provided, of course, that the sewers are used for the purpose for which they are intended, aud that streets and back yards no longer serve as receptacles for filth, as was usual during the presanitary period even in great cities like London and Paris. The axiom 'tout a l'égout' now governs the practice not only in Paris, but wherever the fundamental principles of municipal sanitation are understood and sewers have been constructed. Unfortunately, the cost of sewer construction, the reluctance of tax-payers to part with their money and the ignorance or indifference of municipal authorities have conspired to prevent the accomplishment of this fundamental sanitary measure in very many towns in the United States, and our endemic plague—typhoid fever— continues to claim a large annual quota of victims in such localities. Even in the national capital our sewer system is incomplete and in many out-of-the-way places, especially in the densely populated alleys of the city, shallow box privies are in use as receptacles for human excreta and the typhoid fever rate, owing to this and other causes, is disgracefully high.
Mortality rates in towns and cities throughout the civilized world depend to a large extent upon the purity of the water-supply and the efficiency of the system of sewage disposal; and the constant improvement which is shown by the mortality statistics of England and other countries which have made the most progress in this direction is undoubtedly largely due to these two factors. This is well illustrated by the mortality statistics of armies. In the German army the annual death-rate in 1868 was 6.9 per thousand, a decade later it was 4.82, in 1888 it had fallen to 3.24 and in 1896 to 2.6. In our own army, the death-rate during the period of peace just prior to the Mexican War (1848) was about three and one half times as great as during the five years preceding our recent war with Spain, and since the year 1872 there has been a diminution of the death-rate of nearly forty per cent. In the British army at home stations the mortality rate during the decade ending in 1884 was 7.2 per thousand, in 1889 the rate had fallen to 4.57 and in 1897 to 3.42. In the Italian army there has been a gradual and progressive reduction from 13.3 per thousand in 1875 to 4.2 in 1897. The mortality in the French army was a little over 21 per thousand during the five years ending in 1825. In 1890 it had fallen to 5.81 per thousand.
According to the best estimates the average of human life in the sixteenth century was somewhat less than twenty years. At the present time it is more than twice as long and during the past twenty-five years the average duration of life has been lengthened about six years. During the first thirty-five years of the past century the vital statistics of the city of London showed a mortality of about 29 per thousand. At the present time the mortality in that great city has been reduced to from ​17 to 19 per thousand. I will not burden you with further statistics, but will simply say that even more notable results have been obtained in many parts of the civilized world as a result of increased knowledge and improved methods for the prevention of infectious diseases and the general improvement in hygienic conditions.
The time at my disposal only permits of a brief general survey of the field which comes within the purview of the department of preventive medicine of the Washington Post-Graduate Medical School. It will be our aim during the course to give detailed information and practical laboratory instruction upon all the more important subjects connected with this branch of medicine. This will be apparent to those who have read our 'circular of information' with reference to the course of instruction. This includes personal and municipal hygiene, a practical knowledge of sanitary chemistry, including food adulterations and pathogenic bacteria, of animal parasites injurious to man, of preventive inoculations, of disinfection, of military and naval hygiene, of national and international quarantine, etc. Fortunately we have among our professors, experts upon all of these subjects and we believe that the city of Washington offers unequaled facilities for a comprehensive and scientific course of instruction in preventive medicine. Such a course as would seem best fitting for preparing graduates in medicine for the responsible duties of health officers in the towns and cities throughout the United States, and as is essential for medical officers in the various branches of the public service. But, while we have many special advantages for giving a comprehensive and practical course in the department of preventive medicine, it must not be thought that clinical medicine and surgery are to be neglected. On the contrary, we have ample advantages for clinical instruction in the various hospitals of the city and a corps of competent and experienced professors who are prepared to give practical instruction in all branches of medicine and surgery. Those physicians who enroll themselves as students in the Washington Post-Graduate Medical School and faithfully follow the course of instruction which is open to them, can not fail to return to their professional work with broader and more exact information on many subjects relating to scientific medicine, with increased skill in the diagnosis and treatment of disease and with greater confidence in the resources of the noble profession to which they have devoted their lives.