Annual average of Diphtheria deaths in the quarters of the year.
| 1st qr. | 2nd qr. | 3rd qr. | 4th qr. | |||
| 903 | 713 | 730 | 1025 |
According to some recent returns under the Notification Act, which are of doubtful value owing to the laxity of diagnosis (greater perhaps in throat-disorders than in any other class of diseases), the second and third quarters of the year have also the lowest mortality in proportion to the number of attacks[1376]. As to the ages at which diphtheria proves fatal, they are somewhat similar to those of fatal scarlatina, but slightly higher all over; thus, while two-thirds of the deaths from scarlatina are of infants and children under five years, only one-half of the deaths from diphtheria are under that age. In the first epidemic period, 1855-61, Farr reckoned that 1553 adults had died of diphtheria above the age of twenty-five, while the deaths under that age had been 28,216. In its age-incidence diphtheria is very different from croup, which attacks chiefly children of one, two, and three years of age, the boys dying in greater numbers than the girls[1377]. But in all comparisons between diphtheria and croup, as regards sex and age, it should be kept in mind that many cases of angina of the throat, which end in death by extension to the larynx and trachea, are registered as croup, even in epidemics. Diphtheria is the only epidemic disease besides whooping-cough which is more fatal to female children than to males in proportion to the numbers of each sex living. The following annual average death-rates per million for the period 1855-80 show the higher death-rates of females at certain age periods[1378]:
| All ages | 0- | 1- | 2- | 3- | 4- | 5- | 10- | 15-20 | ||||||||||
| Males | 157 | 490 | 724 | 617 | 667 | 589 | 325 | 107 | 50 | |||||||||
| Females | 168 | 377 | 673 | 668 | 746 | 694 | 413 | 159 | 57 |
It is not until the third year that female children begin to die of diphtheria in excess of males; which means that the usually greater risk to male infants holds good also in this disease for the two first years, while some difference between the sexes becomes thereafter so marked as to turn the balance of fatality to the side of the females. Something of the same kind happens in whooping-cough; and it is probable that in both maladies the cause lies in the earlier acquisition by the male of secondary sexual characters in the throat and larynx, as suggested in the chapter on whooping-cough.
Conditions Favouring Diphtheria.
The circumstances of the great and sudden explosion of diphtheria in 1858 and 1859 are as likely as any to throw light on the causes or determining conditions of the disease. Those two years were remarkable for the Thames running so low in summer as to give out a stench, which was thought to forebode much fever[1379]. The expected epidemic of fever did not come; on the contrary the fever deaths in London were much lower than usual in 1858 and 1859, and, to judge from the few admissions of each kind to the London Fever Hospital, enteric fever declined as well as typhus[1380]. It was diphtheria that came. The lowness of the rivers was due to a succession of years with rainfall below the average:
| Low rainfall | High rainfall | ||||||||
| 1855 | 21·1 | inches | 1865 | 29·0 | inches | ||||
| 1856 | 22·2 | " | 1866 | 30·7 | " | ||||
| 1857 | 21·4 | " | 1867 | 28·4 | " | ||||
| 1858 | 17·8 | " | 1868 | 25·2 | " | ||||
| 1859 | 25·9 | " | 1869 | 24·0 | " | ||||
| Average | 21·7 | " | Average | 27·4 | " | ||||
The low state of the rivers was an index of a low level of the ground-water. If diphtheria is to be included among the infections that have the habitat of their virus in the soil, it will probably be found to be affected by irregularities in the movements of the subsoil water. A series of observations have been made which seem to favour that hypothesis.
At Maidstone in each of the three years 1885, 1886 and 1887, the ground-water rose with the greatest regularity and steadiness to its highest point towards the end of the first quarter of the year, and fell with equal steadiness to its lowest point in the autumn. During two of the years there was little diphtheria, and in one of them none. But, in the next two years, 1888 and 1889, “the levels of the ground-water oscillated to and fro with unwonted frequence,” having several maxima in 1888, and a somewhat uniform high level all through 1889; and during those two years there was a severe outbreak of diphtheria, as well as an excessive number of deaths registered as “croup[1381].”