Etiology.—Typhoid fever is caused by the introduction of the bacillus typhosus into a system not immune to the disease; by its subsequent growth, which occurs usually in glandular structures; and by the development of a special form of poison.
The disease is more prevalent during certain seasons of the year and under certain circumstances, owing either to an increased number and virulence of the micro-organisms or to a lessened power of resistance in the individual.
Age seems to exert an important pre disposing influence. It is rarely found under two years and not often after fifty. A case has been recorded of an infant at six months, and the disease has even been found in the fcetus.
Analysis 2S4 cases of typhoid fever in childhood:— Per- centage.
Up to five years 3 1 Five to ten years 77 27 Ten to fifteen years 201 72 284 Vogel, in 1017 cases, found 412 be tween five and ten years of age and 393 between ten and fifteen. Collectively they show a comparatively small num ber in the first five years, while the re mainder are about equally divided be tween the two other periods. John Lovett Morse (Boston Med. and Surg. Jour., Feb. 27, '90).
Investigations made by means of Wi dal's serum-reaction on 50 cases of sus picious gastro-enteric disturbances in children: 1. Typhoid fever, as has been commonly believed, is an unusual dis ease in infancy. 2. It is possible that women whose blood gives a positive Widal reaction, even though it be years after the occurrence of the disease, may in some way transmit this to their in fants. J. L. Morse and H. W. Thayer (Boston Med. and Surg. Jour., Jan. 12, '99).
Six cases of undoubted typhoid fever met with in patients of two years and under, viz.: nine, thirteen, sixteen, twenty-two, and twenty-four months of age. The diagnosis in all these cases was easily made on signs and symptoms char acteristic of typhoid in adults. The cases were all intimately associated with others in the family. Skepticism should be en couraged concerning any diagnosis of ty phoid fever in an infant (under two years of age) not intimately associated with other cases. The most common mistakes arise from misnaming as typhoid the fol lowing diseases: Grippe, subacute catar rhal enteritis, central pneumonia, and malaria. W. P. Northrup (Presbyterian
Hospital Reports, N. Y., vol. iv, p. 74, 1900).
It is safe to conclude that this reac tion occurs under the same conditions and with the same limitations in chil dren as in adults. There is evidence to show that in them reaction appears earlier, is feebler, and persists a shorter time than in adults. The serum-test, therefore, is of especial value in two ways in the diagnosis of typhoid fever in children: first in ruling out many cases of gastrointestinal disorders which might otherwise be mistaken for typhoid; and, second, in making a posi tive diagnosis possible in many mild cases which might otherwise pass un recognized. J. L. Morse (Archives of Pediatrics, May, 1901).
Cases have also been reported of the disease in patients over seventy years of age. The writer attended during the past year a patient of sixty-eight. In fants are probably exempt on account of lessened exposure, and old people are rendered immune from previous attacks, but these are not altogether sufficient reasons. Infants arc frequently brought up on cows' milk which may contain bacilli, and a large number of individuals pass through middle life without having had typhoid fever. The great majority of cases occur between the ages of fifteen and thirty. Of 1375 cases treated in the Toronto General Hospital from 1590 '97, inclusive, 1016 occurred between the ages of ten and thirty. The mean age in 1772 cases, according to Murchison, was twenty-one years.
Males and females seem equally liable to the disease, although in hospital sta tistics males predominate. Of 1375 To ronto Hospital cases, S74 were males and 504 females. According to some sta tistics, boys are more frequently affected than girls. This may arise, as Wilson has pointed out, from the fact that boys, in their out-door sports, are more exposed by drinking impure water.
The great majority of cases occur dur ing the last four months of the year, and from February to May there is a com parative freedom from the disease. Spe cial epidemics may take place at any season and some of the most severe have prevailed during the spring months. Eight hundred and twenty-eight of the 1375 Toronto cases came into the hos pital during the last four months of the year.