18 A Treatise on Continued Fevers, London, 1873.
GEOGRAPHICAL DISTRIBUTION.—Although it will be generally admitted that the conditions of civilization favor the occurrence and extension of typhoid fever, yet there is abundant evidence that they are not absolutely necessary to its production, as there is no country, whether civilized or not, of the diseases of which we have any knowledge, in which it has not occasionally made its appearance, being met with in every variety of climate. It is endemic in North America, attacking alike the inhabitants of Greenland and British America and those of Mexico. In our own country it prevails from time to time in every State of the Union, committing its ravages as well among the rocks and hills of New England as in the more fertile valleys of the West and South. In many of the newly-settled portions of our country malarial fevers are, as is well known, exceedingly rife. In proportion, however, as towns and cities spring up, and as the land is properly drained, they diminish in frequency, and are gradually replaced, to a certain extent at least, by typhoid fever; but the influences which produced them retain for a long time enough of power to stamp their impress upon all other diseases. In large portions of the Western and Southern States typhoid fever is therefore rarely uncomplicated, and is much more likely to assume the form which will be fully described later as typho-malarial fever.
Typhoid fever has also occurred frequently in Central America and the West India Islands. It has prevailed from time to time in the states of South America, and occasionally assumed in some of them—as, for instance, Brazil and Chili—an epidemic form.
Typhoid fever is endemic in the British Isles, but, according to Murchison, is most common in England, more common in Ireland than in Scotland, and in Scotland more common on the west than on the east coast. It also exists as an endemic disease in every country of the continent of Europe, from Sweden and Norway on the north to Turkey on the south, and in some of them—as, for instance, France and Germany—would seem to be of much more frequent occurrence than in this country, or even in England. Medical literature is also not deficient in evidence that it has prevailed at various times in all the different countries of Asia and Africa and in Australia. Morehead asserted in the first edition of his Clinical Researches on Diseases in India that India enjoyed an absolute immunity from typhoid fever, but in the second edition of this work he acknowledged that a larger experience had led him to change his opinion on this point. Moreover, the writings of Annesley, Twining, and other Indian authors furnish convincing proof that the disease is by no means unknown in that country. Indeed, even the relative immunity from it which it has been claimed that tropical and subtropical countries possess has been found, upon a fuller study of the diseases of these countries, not to exist to anything like the degree that was formerly supposed.
The occasional occurrence of typhoid fever in islands separated from the main land by a considerable distance—as, for instance, the island of Norfolk,19 which is situated in the Pacific Ocean four hundred miles west of South America—is an interesting fact, and one which, with the present limits to our knowledge on the subject, it is impossible to explain satisfactorily.
19 Metcalfe, Brit. Med. Jour., Nov., 1880.
The ETIOLOGY of typhoid fever may be considered under the heads of—1, predisposing, 2, exciting causes.
1. PREDISPOSING CAUSES.—All observers agree that the predisposition to typhoid fever is greater in childhood and early adult life than after thirty years of age. Thus, Murchison states that during twenty-three years nearly one-half the admissions to the London Fever Hospital were of patients between fifteen and twenty-five years of age, and that in more than a fourth, the patients were under fifteen years. On the other hand, in less than a seventh were they over thirty, and in only one in seventy-one did their ages exceed fifty. Taking these facts in connection with the circumstance that the entire population of England and Wales in 1861 was 12,481,323 persons under thirty years of age and 7,584,901 above thirty, it follows, he says, that persons under thirty are more than four times as liable to enteric fever as persons over thirty. Jackson found that the average age of the patients in two hundred and ninety-one cases observed at the Massachusetts General Hospital was a little over twenty-two years, the average age in the fatal cases being somewhat greater than in those in which recovery took place. Liebermeister, from an analysis of a large number of cases treated at the hospital in Basle, has arrived at the same conclusion. No age, however, enjoys a complete immunity from the disease. Manzini20 has recorded a case in which lesions of Peyer's patches similar to those of typhoid fever were found in a seventh-month foetus which died within half an hour after its birth. Cases are also on record in which death has occurred from this disease in the first few weeks of life. I have myself observed several cases in young children at the Children's Hospital in Philadelphia. The probability is, that it is of even more frequent occurrence in children than is generally supposed, as this class of patients is not often admitted into general hospitals, and as from the absence of some of its characteristic symptoms when it occurs in the very young the nature of the disease is often unrecognized.
20 Quoted by Murchison.
On the other hand, the disease occurs not infrequently in advanced life: 83 cases out of 5911 were observed at the London Fever Hospital in persons over fifty, 27 in persons over sixty, and in 2 the age was seventy-five. In a case recorded by D'Arcy the age of the patient was eighty-six, and in one reported by Hamernyk it was ninety.21 Bartlett long ago contended that the disease was not so rare as was generally supposed among people over forty years of age; and there is really no good reason to believe that the susceptibility to the causes of the disease in an unprotected person diminishes with advancing years, the immunity from this disease which elderly people appear to enjoy being probably due to the fact that, as the disease is not uncommon in early life, they are in many instances protected by having already passed through an attack.