I have seen no reason for revoking the conclusion expressed in 1908 in a lecture to the Washington International Congress on Tuberculosis that historically the hospital treatment and coincident segregation of patients suffering from pulmonary tuberculosis has been an important and probably a dominant factor in producing the national decline in the death-rate from tuberculosis in the countries in which a decline has been experienced. This explanation fits in with our knowledge of the disease, and with the analogous history of leprosy; and it is supported by the fact that by complete segregation of infected from non-infected cattle tuberculosis can be eliminated at will from a herd of cattle. It is remarkable, as I have elsewhere set out in much detail, that improved general health, increased well-being, and sanitary education have operated in Great Britain, Germany, Belgium, Denmark, and Massachusetts side by side with great decrease in the death-rate from pulmonary tuberculosis; while up to very recent years the same influences in France, Norway, and Ireland have produced little or no decrease in the national death-rate from tuberculosis. And similarly no constant relation can be shown between the degree of sanitary and social well-being in different countries and cities, and the amount of mortality imposed by tuberculosis. How is it that in some countries a high degree of domestic overcrowding is associated with a low and declining phthisis death-rate and conversely that a persistently high phthisis death-rate may occur with a less but still diminishing degree of overcrowding? The explanation is contained, I maintain, in the following statement:
A given amount of domestic overcrowding with a large amount of institutional segregation of consumptives is associated with less tuberculosis than when overcrowding is less but accompanied by only a small amount of institutional segregation of consumptives. The data as to institutional segregation are difficult to obtain; but there is sufficient evidence to show that in countries which have experienced a large reduction in the death-rate from tuberculosis a large proportion of hospital treatment for many years has been provided for consumptives, while in countries which have not experienced this decline such provision has been absent or imperfect. In London about 56 per cent., in county boroughs 35 per cent., in other urban districts 21 per cent., and even in rural districts of England near 16 per cent. of all deaths from pulmonary tuberculosis occur in hospitals (poor-law institutions, general and special hospitals, and asylums). Prior to the patient’s death he has had on an average at least three months, and probably in the aggregate more nearly five or six months, residential treatment, and this at the stages of disease in which there is the greatest discharge of infective material, in which owing to feebleness the patient is least able to control its hygienic disposal, and in which—had the patient been treated at home—the relatives would be especially liable to receive massive infection, and would be enfeebled by overwork and anxiety, or by the malnutrition associated with poverty.
Some writers have failed to visualize the fact that the segregation of a minority of the total cases of pulmonary tuberculosis for a portion of their illness can have had a marked influence on the prevalence of this disease. They appear to be judging tuberculosis by the same measure as they would apply to smallpox, which in an unprotected community spreads rapidly if a few cases are overlooked. The case of tuberculosis, like that of leprosy, is governed by the considerations that both these diseases as a rule require intimate and protracted contact for their spread, and that in both diseases there may be prolonged latency before active disease develops. A hypothetical illustration may serve to elucidate the order of magnitude of the influence exercised by institutional segregation. Let us assume—as is probably the case in England—that one-fifth of the cases of pulmonary tuberculosis are treated during one-third of a year institutionally under conditions in which they will not be liable to spread infection. Let us assume further that each of these cases has an infectious lifetime of three years. Thus one-fifth of the cases are deprived of their power to spread infection during one-ninth of their period of “open” disease. It being assumed that personal infection causes pulmonary tuberculosis and that segregation is efficient, segregation to the extent indicated above should secure a reduction in the death-rate from pulmonary tuberculosis of 100/(5 × 9) approximately 2 per cent.
In actual fact the decline in the English death-rate from pulmonary tuberculosis since 1871 has been at a rate slightly under 2 per cent. per annum.
Koch’s Endorsement of Segregation View
An extract from an article written by Robert Koch shortly before his death may be permitted (Epidemiologie der Tuberkulose Zeitschr. für Hyg. und Infektious Krankheiten. 4. XVII, 1910).
I am entirely in agreement with Newsholme that the allocation of consumptives to institutions for the sick, as freely as possible and for as long as possible, is the most active means of avoiding infection and the consequent spread of phthisis.
In my experience, too, phthisis has shown the most marked decline in those places where comprehensive measures have been taken for bringing consumptives into hospitals, and the converse has been the case where the converse conditions prevail. It is indeed obvious that in no other way can the danger of infection, which a phthisical patient constitutes, be so effectively removed as by isolation in hospital. Strong support of this method is afforded by leprosy, where good results in attacking the disease have been obtained by following the same principle.
In addition to this factor there is a second, which also plays a very important part, viz., housing.
A hypothesis explanatory of a given phenomenon should be consistent with all the associated facts. We have seen that the hypothesis that segregation of consumptives is an important factor in the reduction of the death-rate from pulmonary tuberculosis agrees (1) with our knowledge of the tubercle bacillus, and (2) with veterinary and agricultural experience; also (3) that,—although exact data are unobtainable,—the degree of segregation when ascertainable is consistent with the degree of decline in the death-rate; (4) it is important to note also that this hypothesis is consistent with the otherwise anomalous facts that although the proportion of the population subjected to urban conditions of life has steadily increased, and the number of persons per inhabited room remains much greater in towns than in country districts, the death-rate from pulmonary tuberculosis in England has declined as much in them as in country districts; and that notwithstanding the greater overcrowding in towns, the urban is rapidly falling to the level of the rural death-rate from this disease. The town dweller’s better and more frequent treatment in hospitals is an important factor in overcoming the handicap of urban conditions of life, including overcrowding and preponderance of indoor and dusty occupations.