CHAPTER XXVI. CONDITIONS WHICH FAVOR THE ORIGIN AND DISSEMINATION OF CHOLERA. It seems necessary to state explicitly that whether we accept the doctrine of the parasitic origin of cholera or not, we must still recognize certain secondary causes favorable to its breaking out and propagation. It will be our duty now to examine some of these favoring conditions, which are much less in dispute than the immediate exciting cause of the disease, although writers are by no means agreed in ascribing the same amount of potency to the different agencies in question. The whole history of cholera shows it to be emphatically a disease spread by human intercourse. It does not travel quicker by land or water than man. Nor does it spread in directions unknown to commercial or military movements. On land it has usually crept from place to place, and if sometimes it has seemed to leap across wide spaces, and even seas and oceans, it has never invaded any inland town or seaport without having been brought thither from a point already affected with the disease. Nor, having once entered an inland or seaboard town, does it spread equally therein in all directions, but prevails chiefly in the quarter immediately surrounding the place of its entrance. If appropriate sanitary measures are enforced, it is sometimes confined to that quarter, and, in the case of quarantine stations, it has repeatedly been prevented from extending beyond them. This statement may be illustrated by the fact that of fourteen epidemics of cholera at Staten Island, the quarantine station of New York, all but four were prevented from reaching that city. When the disease does overleap the barrier opposed to it, its origin and subsequent course can usually be traced (Stillé). It goes without saying that the individual may become more or less predisposed through his circumstances in life, his personal habits, and his surroundings. But the causes operative in this respect are the same deleterious influences favoring the acquisition of all other infectious and preventable diseases. Poverty, with its incidental conditions of bad air, filth, overcrowding, intemperance and other excesses, doubtless favor the acquisition of cholera, but acting independently of the specific poison of the disease, they are utterly impotent. The relative mortality from cholera is, therefore, not more excessive among the poor and shiftless than that of other diseases fostered by unhygienic living and the weakening effects of insufficient or improper food and air. As regards the sex of individuals, it does not seem that one is more liable to take cholera than the other. 'Peters' Notes, 2d ed., p. 94. Age is of greater importance than sex. The liability to fatal attacks increases after 45 in a very decided manner. In England, according to Gull, the greatest fatality occurred under one year and over fifty-five. The liability to contract the disease appears to be greatest between the ages of 15 and 40, and it is noteworthy that the relative mortality is the slightest for about the same period. Infants under one year of age are not specially prone to acquire cholera, but when they do take the disease, the result is almost invariably fatal. Occupation does not appear to influence the liability to cholera. In a general way, of course, unhealthy and very fatiguing work by weakening the system renders it more liable to the inroads of disease. But this does not apply especially to cholera. Habits, as already intimated, may influence the susceptibility to cholera in a more or less pronounced way. It is held by writers that habitual drunkards, before the stage of organic visceral changes, are no more prone to the disease than the temperate. Indeed, it is supposed by some authors that habitual drunkards belonging to the better classes enjoy a relative immunity from the disease, on account of their avoidance of water that may have become contaminated. The weight of evidence, however, favors the opinion that alcoholic drinks may assist the production of cholera. It was found that during the cholera epidemic of 1848-9 in England the deaths from cholera on Saturday, Monday, Tuesday and Wednesday were above, and on Thursday, Friday and Sunday, below the average. The weekly wages are generally paid on the Saturdays, and the Mondays in London and other cities are days on which a certain proportion of the population indulge in intoxicating drinks. During the epidemic of 1865 the mortality in Berlin suddenly rose on certain days, and was clearly referable to excess in drinking. In 1866, Dr. Andrew Clark stated, in respect to the London Hospital, that immediately after pay-day among workmen there was a great influx of cholera patients. When the epidemic of cholera broke out at Naples in the beginning of September, the Pungola, a Neapolitan newspaper, attributed the increased number of cases to intemperate living on the 31st of August, which was a féte day (Chapman). In an interesting article on the germ-theory of zymotic diseases, Dr. W. B. Carpenter' makes the following allusion to alcoholic excesses: The experience of cholera-epidemics has presented numerous examples which testify to the evil results of intemperance; but I know of no case in which the benefits of extreme temperance, in keeping at bay the operation of a zymotic poison, were more remarkable than in the contrast between the march of the 84th Regiment (of which Dr. E. Parkes was at that time assistant-surgeon) from Madras to Secunderabad, in 1847, and the concurrent march of the 63d Regiment from Secunderabad to Madras. The former had been previously quartered for several months in healthy barracks; a large number of men were total abstainers, while the rest were very temperate; and their death-rate had been no more than 12.1 in 1,000 per annum. The latter had been overcrowded in the barracks at Secunderabad; though not specially intemperate, they habitually indulged in alcoholics, and their death-rate had been 78.8. The two marches were made at the same time, in opposite directions, in a very wet and unhealthy season, through a country infested with cholera and fever; and while the 84th was almost entirely free from these diseases, the 63d had so many sick when the two regiments crossed on the road, as to be obliged to borrow the 84th's sick-palanquins. Now since, in both these cases, the infecting cause must have operated alike on all, it is clear that in whatever way the cholera-germs are received into the human body, it is on the previous condition of each individual that their potency depends, and that this condition is induced by any causes which engender in this circulating fluid a suitable pabulum for their growth and multiplication. Dissolute habits generally, venereal excesses, uncleanliness, do not ap 1 Nineteenth Century Review. February, 1884. Psychical influences are of unquestionable importance in favoring an attack of cholera. Nervousness, anxiety, depression of spirits, grief, fear, violent emotions, and even actual insanity would all appear to predispose the individual to contract the disease. Dr. Forbes Winslow has said that, cæteris paribus, the patient who has the least fear of dying during an attack of cholera has the best chance of living. Apart from these individual factors, there are a number of other cireumstances that appear to facilitate the production and propogation of cholera. Yet once more it must be repeated that, while they may impart energy to the virulence of the disease and favor its rapid spread, they have not the slightest power to produce cholera independently of the existence of its specific poison. General Atmospheric Conditions.-Cholera may prevail under very wide ranges of temperature, humidity and barometric pressure. Nevertheless a certain amount of heat, a high atmospheric pressure, and moderate humidity appear to favor the disease. In India cholera is at its worst during the hottest months, and there appears in this respect but little difference between dry and wet heat. In Calcutta, however, Lewis and Cunningham did not find that temperature exerts any influence on the variations in the prevalence of cholera, except in a subordinate way. For maximum, minimum and medium prevalence were observed by them in an almost unaltered temperature. In England (in 1848-49) the highest mortality occurred in September. But in continental Europe cholera prevailed extensively during the cold. weather of the same year. The association of heat with moisture certainly favors the spread of cholera. For example, Thom. in his report of the violent outbreak at Kurrachee, states that there was a very high dew point (83°), and a temperature of 90° F. in the shade. This led to a sense of languor and oppression, stifled breathing, and great fatigue on slight exertion. Goodeve states that: A warm, moist, stagnant atmosphere in Bengal, at any time of the year, is often followed by sporadic cases of cholera, or by an increase of cases where the disease is endemic. Cholera has been known to cease after heavy falls of rain, and, on the other hand, to set in immediately afterward, as in the Meerut jail in 1861. In considering the influence of rain, we must recollect the temperature prevailing and the time that has elapsed after the said fall. A very few hours after a fall of even heavy rain, if there be no wind, is sufficient to produce just the stagnant, hot and moist atmosphere which is so oppressive to the feelings, and favors so much the spread of cholera. One must not be misled by the name of dry months. The hot months in Calcutta are called the dry months, and are, indeed, the driest of the year, yet a great deal of moisture exists dissolved in the warm atmosphere. Lewis and Cunningham, who have made quite an elaborate study of the physical phenomena of India in relation to cholera, report that there is a certain amount of coincidence between diminished humidity and increased cholera prevalence in Calcutta. They say: We have maximum prevalence and minimum humidity in March; and minimum prevalence and maximum humidity in August. With especial reference to the influence of rainfall, these observers state that there is nothing to justify the belief that rainfall in Calcutta exerts any direct action either in producing or diffusing the essential cause of cholera; but, on the other hand, there is some evidence that excessive rainfall exerts a directly opposite action. It is proper to point out in this connection that moisture and heat favor the growth and development of the comma-bacilli. And further that a heavy rainfall may so dilute contaminated pools and wells as to lessen the chances of infection. Still it should not be forgotten that cholera has been known to speedily follow a severe thunder-storm. The cessation of autumn epidemics of cholera on the approach of winter is a well-established fact. Nevertheless the disease may survive even a very cold winter, as has been several times observed. Cold does not kill the bacilli of cholera, although it appears to hinder their active proliferation. Hirsch has found from a study of 341 outbreaks in different countries, that cholera has appeared in nearly half of all the epidemies during the summer, and chiefly in July and August. Winter is characterized by an unmistakable exemption from the disease. Electricity, Ozone and Cosmical Influences.-In spite of the very positive assertions of some writers, it does not appear that either of these factors, or all combined, are decidedly influential in promoting the spread of cholera. But to deny them all potency for assisting the disease would be to err on the other side. Mr. Glaisher has made a number of interesting observations touching these points, which are found in the appendix to the Cholera Report for 1853-54, and in the report of the Indian Sanitary Commission (1862). In his report on the Meteorology of London during the three cholera epidemics of 1832, of 1848-9, and of 1853-4, he found that they were attended with a particular state of atmosphere, characterized by a prevalent mist, thin in high places, dense in low, during the height of the epidemic. In all cases the reading of the barometer was remarkably high, and the atmosphere thick. In 1849 and 1854 the temperature was above its average, and a total absence of rain and a stillness of air amounting almost to calm accompanied the progress on each occasion. In places near the river the night temperatures were high with small diurnal range, a dense torpid mist, and the air charged with many impurities arising from the exhalations of the river and adjoining marshes, a deficiency of electricity, and, as shown in 1854, a total absence of ozone, most probably destroyed by the decomposition of organic matter with which the air in these situations is strongly charged. In 1849 and 1854 the first decline of the disease was marked by a decrease in the readings of the barometer and in the temperature of the air and water; the air, which previously for a long time had continued calm, was succeeded by a strong southwest wind which soon dissipated the former stagnant and poisonous atmosphere. In both periods at the end of September the temperature of the Thames fell below 60°; but in 1854 the barometer again increased, the air became again stagnant, and the decline of the disease was considerably checked. It continued, however, to subside, although the months of November and December were nearly as misty as that of September. Soil. It has not been conclusively shown, although there are very positive assertions to the contrary, that the nature of the soil has any very decided influence on the appearance and spread of cholera. But to deny this factor all importance would be to err in an opposite direction. According to McClellan, stiff and clayey soils have shown a higher mortality than loose, sandy and easily drainable ground. Farr said that cholera was less fatal in England on primary geological formations than on others. Black cotton soil was found to exist in nearly half the epidemics examined by Lorimer (Goodeve). |