The age-incidence of Smallpox in various periods of history.

CHAPTER V.

Among the various changes of incidence that have attended the recent decline of smallpox in England, Ireland and Scotland, there is one that calls for more extended notice, namely, the fact that the malady has in great part ceased to be an infection of infancy and childhood and has become more distinctively an infection of adolescence and mature age. In no period of its history has smallpox been so purely an infantile complaint as measles[1175], nor so purely a malady of childhood and early youth as scarlatina or diphtheria[1176]. When it first rose to prominence in England, from the reign of James I. onwards, it attacked adults in a large proportion; of which fact the evidence, although not statistical, is sufficient. But, as the disease became nearly universal and ubiquitous, it was so commonly passed in infancy or childhood, that few grew to maturity without having had it. The number of adult cases diminished in proportion as the disease became more nearly universal. In the great period of smallpox in the 18th century, about nine-tenths of the deaths occurred under the age of five, and nearly all the remaining fraction between five and ten years, at Manchester, Chester, Warrington, Carlisle and Kilmarnock. But in London there were always a good many adult deaths, the reason commonly given being that there was a steady influx to the capital of domestic servants and others from country parishes where the epidemics came at sufficiently long intervals to let many children grow up without incurring the risk of it. Also at Geneva and the Hague, in the 18th century, there were many more deaths above the age of five than in the English provincial towns at the same time.

Ages at Death from Smallpox at Geneva (including Measles) and at the Hague (Duvillard).

	All ages	0-1	-2	-3	-4	-5	-6	-7	-8	-9	-10	-15	-20	-25	-30	-35	-40	-45
Geneva (1700-83)	3328	555	608	588	426	346	232	185	99	67	44	84	36	26	21	0	0	0
The Hague (15 years of 18th cent.)	1455	172	170	179	224	160	148	114	78	58	23	47	17	24	14	10	8	3

Twenty-four per cent. of the smallpox deaths in the 18th century at Geneva were above the age of five years, and at the Hague thirty-seven per cent., while in the former the ratio would probably have been higher but for the inclusion of measles. But, with this comparatively high ratio of deaths above the age of five, smallpox was a much less important cause of mortality at Geneva and the Hague than at Manchester, Glasgow, Chester, and most other provincial cities of this country, making about a fifteenth part of the deaths from all causes in the former, and as high as a sixth part in the latter.

The infantile character of smallpox was as marked as ever in the epidemic of 1817-19; of which the Norwich statistics are sufficient proof. As late as the epidemic of 1837-40, smallpox was still distinctively a malady of infants and young children in Britain, although that was by no means the case on the continent of Europe at the same time. The following was the age-incidence of fatal smallpox at Liverpool and Bath in the last six months of 1837.

		At all ages	Under 1	1-2	2-3	3-4	4-5	5-6	6-10	Above 10
Liverpool	Deaths	495	143	127	77	64	24	19	20	25
Liverpool	Ratios per cent.	100	28·65	25·45	15·43	17·63		7·81		5·01

Bath	Deaths	151	33	31	33	17	17	6	6	10
Bath	Ratios per cent.	100	21·56	20·26	21·56	22·2		7·84		6·53

In the third year of the epidemic, 1839, the ratio of deaths above the age of five was still less at Manchester, Liverpool and Birmingham, being only four and a half per cent. (26 in a total of 522). At Glasgow, from 1835 to 1839, twelve per cent. of the smallpox deaths were above the age of five (see p. 600). These are the rates of provincial cities; but in a total of 8714 deaths in the year 1839, added together from London and the provinces, about twenty-five per cent. were over five, and of these a moiety were over ten years:

All ages		Under five		Five to ten		Above ten
8714		6453		1122		1139

A good deal of that mortality above the age of five must have come from London, according to the probability of the following table, which is of six years’ later date, but the nearest that can be got for London alone:

London, 1845. Ages at Death from Smallpox, Measles and Scarlatina.

	Smallpox	Measles	Scarlatina
Total at all ages	909	2318	1085
Under One year	209	353	88
One to Two	133	832	167
Two to Three	91	511	181
Three to Four	81	272	183
Four to Five	63	153	115
Five to Ten	136	168	254
Ten to Fifteen	33	18	46
Fifteen to Twenty	34	3	14
Twenty to Twenty-five	54	1	8
Twenty-five to Thirty	38	2	6
Above Thirty	37	5	23

The ratio of smallpox deaths above five was 37·5 per cent., of measles deaths 8·4 per cent., and of scarlatina deaths 32·3 per cent. Measles and scarlatina have kept these ratios somewhat uniformly to the present time, but the ratio of smallpox deaths above the age of five has increased according to the following table for England and Wales from 1851 to 1890:

The progressive raising of the age of fatal smallpox is shown in another way by taking the ratio of the deaths per million living at all ages and at each of eleven age-periods[1177]:

Smallpox Deaths per million living at each age-period.

Period	All ages	0-	5-	10-	15-	20-	25-	-35	-45	-55	-65	75 and over
1851-60	221	1034	257	73	93	130	92	53	38	24	18	14
1861-70	163	654	145	56	86	136	102	73	49	36	26	22
1871-80	236	527	284	137	197	300	239	168	111	71	46	35

It was the great epidemic of 1871-72 that brought out the change of age-incidence most concretely, just as it brought out, in contrast to the last great epidemic in 1837-40, the decline in the rural and the increase in the industrial centres. In the three years before the outburst of 1871 the deaths under five and over five were approaching an equality; in the epidemic itself the old ratios were suddenly reversed:

Year	Smallpox deaths under five	Smallpox deaths over five
1868	1234	818
1869	892	673
1870	1245	1375
1871	7770	15356
1872	5758	13336

In the whole generation between 1840 and 1871, in which there was no great and general epidemic of smallpox, many had passed from childhood to adolescence and maturity without encountering the risk of it. When the epidemic of 1871 began, it found many in youth or mature years who had not been through the smallpox, and it attacked a certain proportion of them accordingly. The proportion above the age of five so attacked in 1871-72 was greater than it had been in this country since the beginning of the 18th century; indeed, as the information is not in statistical form for the earlier period, it may be asserted, and it may happen to be true, that it was greater than it had ever been in this country at any time. The reason for the large proportion of adult cases was the same in the rise of smallpox as in its decline, namely, that in the respective circumstances an epidemic found many who had not been through the disease in infancy or childhood. The same happened in those parts of the world where the epidemics of smallpox came at long intervals, during which many had passed from childhood to youth or mature age without once encountering the risk of smallpox.

Such were the epidemics at Boston, New England, and Charleston, South Carolina, in the 18th century. Not only do the accounts of them speak of the disease as if it were mainly one of the higher ages, but it follows from the ratio of attacks to population, known in the case of Boston, that adolescence and adult age must have had a full share, considering that these age-periods included all who were protected by a previous attack. The years of epidemic smallpox at Boston were 1702, 1721, 1730 and 1752: of these four the two worst were 1721 and 1752, the one epidemic following a clear interval of nineteen years, the other a more or less clear interval of twenty-two years:

Smallpox in Boston, Massachusetts[1178].

	Population, whites and blacks	Attacked by smallpox	Died of smallpox	Had smallpox before	Moved out of town
1721	10,565	5989	844	All the rest less 750	—
1752	15,684	5545	569	5598	1843

These enormous mortalities in Boston were comparable to those of the old plague itself in European cities, not only in falling upon all ages but also in doubling or trebling for a single year at long intervals the annual average of deaths:

		Deaths of whites	Deaths of blacks	Total
	1701	146	—	146
*	1702	441	—	441

	1720	261	68	329
*	1721	968	134	1102
	1722	240	33	273

*	1730	740	160	909
	1731	318	90	408

*	1752	893	116	1009

* Smallpox years.

Just as smallpox in its first great outbursts in the London of the Stuarts, or in its rare outbreaks in the American colonies in the 18th century, fell impartially upon children and adults, so in its last outbursts in the London of Victoria it fell upon persons at all ages. The notable thing is, not that smallpox should have of late been attacking adults, for that it has ever done except in times and places in which there were few or no adults who had not been through the disease in childhood; but that it should have ceased to so large an extent to attack infants and children. It has ceased to attack infants and children because other infective and non-infective diseases more appropriate to the modern conditions of the population are attacking them instead. These are measles and whooping-cough, scarlatina and diphtheria, infantile diarrhoea, and the more chronic after-effects of these. The annual death-rate from all diseases under the age of five has fluctuated somewhat per million living from 1837 to the present time, but it can hardly be said that it has fallen much or steadily[1179].

Keeping still to the epidemic of 1871-72, let us consider whether there was any natural or epidemiological reason for its cutting off a smaller ratio of infants and children in its whole mortality than that of 1837-40 did. There had been a most disastrous epidemic of scarlatina for three years just before, which had caused 21,912 deaths in 1868, 27,641 in 1869, and 32,543 in 1870, a total of 82,096 in three years, about two-thirds of which were under the age of five, or at the age-period which smallpox used to be fatal to almost exclusively and to be the greatest single epidemic scourge of. Even in the two smallpox years themselves the scarlatinal deaths were 18,567 and 11,922, of which the share that fell to children under five was one and a half times the deaths in that age-period from the co-existing smallpox. The three years of excessive scarlatina, before the epidemic of smallpox began, had removed large numbers of the class of infants and children who succumb to any infectious disease; if we cannot give the whole rationale of one infection dispossessing or anticipating another, we can at least understand that the earlier and more dominant infection takes off the likely subjects. What scarlatina did egregiously during the three years just before the great explosion of smallpox, it had been doing steadily (along with measles, &c.) throughout a whole generation since the last great sacrifice of infants and children by smallpox in 1837-40. But the fact that scarlatina had in great part dispossessed smallpox among the factors of mortality under the age of five, did not prevent the latter infection from attacking those of the higher ages who were susceptible of it and were at the same time unvexed by any other great epidemic malady proper to their time of life. If the epidemic of smallpox in 1871-72 had cut off as large a ratio under the age of five years as its immediate predecessor in 1837-40 did, its whole mortality would have been about 70,000 more than it actually was. But in no state of the population or of the public health can we suppose that three years of excessive mortality of children by one kind of contagion would be followed immediately by two years of equally special mortality at the same ages by contagion of another kind. It is not only epidemiological science that tells us this, but also common sense—est modus in rebus.

The saving of life by checking the prevalence of smallpox was a favourite rhetorical topic in the 18th century. Voltaire, La Condamine, Bernoulli, Watson, Haygarth and others, were fond of estimating how many thousands of lives might be saved in a year if inoculation were thoroughly carried out. Dr Lettsom, Sir Thomas Bernard and Mr James Neild, who were interested in prison reforms and in whatever else would reduce the prevalence of typhus, reckoned the possible saving of life under that head as almost equal to the possible saving from smallpox[1180]. For typhus there was no artificial means of restraint; it had to decline before natural causes, if it declined at all,—which, indeed, it has done. But no one at that time thought of keeping down smallpox except by the inoculation of itself or of cowpox. The economists and statisticians treated each of these artifices in its turn as a factor having a certain absolute value, which they might use like the a and b of a problem in algebra. This they did, of course, in deference to medical authority. What Bernoulli had worked out for the old inoculation, Duvillard did for the new, in his “Tables showing the Influence of Smallpox on the Mortality of each period of Life, and the Influence that such a preservative as Vaccine may have on the Population and on Longevity[1181].” Malthus fell into the conventional way of thinking when he assumed that smallpox alone among the epidemic checks of population was to be controlled artificially; but he introduced an important new consideration. “For my own part,” he wrote in 1803, “I feel not the slightest doubt, that if the introduction of the cowpox should extirpate the smallpox, and yet the number of marriages continue the same, we shall find a very perceptible difference in the increased mortality of some other diseases[1182].”

Five years after this was written, there came, in 1808, the disastrous epidemic of measles, which in Glasgow killed more infants in a few months than smallpox had ever done at its worst in the same city. In the winter of 1811-12 there was another severe epidemic of measles in Glasgow; and in 1813, Dr Watt, a leading physician of the place, and a man now famous in all countries for his vast labours as a bibliographer, gave to the world his statistical proof, from the Glasgow burial registers, of that law of substitution which Malthus had found necessary in his deduced principles.

“The first thing,” said Watt, “that strikes the mind in surveying the preceding Table (1783-1812), is the vast diminution in the proportion of deaths by the smallpox, a reduction from 19·55 to 3·90. But the increase in the subsequent column [measles] is still more remarkable, an increase from 0·95 to 10·76. In the smallpox we have the deaths reduced to nearly a fifth of what they were twenty-five years ago [in ratio of the deaths from all causes]; in the same period the deaths by measles have increased more than eleven times. This is a fact so striking that I am astonished it has not attracted the notice of older practitioners, who have had it in their power to compare the mortality by measles in former periods with what all of them must have experienced during the last five years[1183].”

The high ratio of measles and the low ratio of smallpox did not remain as Watt’s researches left them. When Cowan resumed the tabulation of figures from 1835 to 1839 he found the ratios of those two infantile infections almost equal, and the two together contributing to the whole mortality of Glasgow only a little more than half their joint share in the end of the 18th century. The substitution which Watt saw during a few years was only the most dramatic part of a general movement forwards of measles among the causes of infantile mortality. He supposed, as everyone did at that time, that smallpox was forcibly repressed, and that another infectious disease had seized the opportunity to become exuberant. The most relevant thing in the whole situation was urged by those who thought, with Jenner, that the doctrine of substitution had an “evil tendency” as detracting from the absolute value of the inoculation principle. In order to discredit Dr Watt altogether, they pointed out that his ratios of smallpox and measles took no account of the diminished death-rate of Glasgow by all diseases in the earlier years of the 19th century.

Great changes were proceeding in the old city, the Glasgow of ‘Rob Roy.’ The population which was reckoned at 45,889 in the year 1785, had increased to 66,578 in the year 1791, and thereafter, at a slower rate, to 83,769 in 1801 and to 100,749 in 1811. The first great increase after the American War meant overcrowding; but in a short time new suburbs spread over such an extent that, in the year 1798, more than half the burials were in the graveyards attached to chapels-of-ease and meeting-houses outside the original parishes. The modern expansion of Glasgow, like that of London and of all other large cities, has been an increase of area still more than an increase of numbers. The public health improved steadily, at all events until 1817, the improvement being shown first in the increasing number of infants that survived their second year. That rise in the probability of life corresponded to the substitution of measles for smallpox, and in part depended upon the ascendancy of the milder infection. Still more remarkable was the rise of scarlatina, which Dr Watt did not live to see; so little was made of it at the date of his writing that he found “scarlatina, typhus, &c., all comprehended under the same head.” The seeds of measles and scarlatina had long existed beside the seeds of smallpox, but the ascendancy of each of the two former had to wait events. Said Banquo to the witches who hailed Macbeth as king and himself as the sire of later kings:

“If you can look into the seeds of time,
And say which grain will grow, and which will not—”

The succession of reigning infections is the same problem. All we can say is that each new predominant type is somehow suited to the changed conditions. In the long period covered by this history we have seen much coming and going among the epidemic infections, in some cases a dramatic and abrupt entrance or exit, in other cases a gradual and unperceived substitution. Some of the greatest of those changes have fallen within the two hundred years since Sydenham kept notes of the prevalent epidemics of London. We are that posterity, or a generation of it, which he expected would have its own proper experiences of epidemics and at the same time would know all that had passed meanwhile—“posteris quibus integrum epidemicorum curriculum venientibus annis sibi invicem succedentium intueri dabitur.”

Percentage of
smallpox deaths
above five years

Percentage of
measles deaths
above five years

Percentage of
scarlatina deaths
above five years

MEASLES.

In the earliest English writings on medicine, measles is the inseparable companion of smallpox; so closely are they joined in pathology and treatment that even the statements as to the pustules and scars of the eruption are in some compends made to apply to both without distinction. This singular conjunction of two diseases came originally from the Arabian teaching, which was everywhere authoritative in the medieval period, and especially authoritative in all that related to smallpox. In the Latin compends based upon Avicenna or other Arabic writers, the two names were variolae and morbilli, the former being as it were the morbus proper and the latter its diminutive. It can hardly be doubted that we owe the English name of measles as the equivalent of morbilli to John of Gaddesden. Originally the English word meant the leprous, first in the Latin form miselli and misellae (diminutive of miser), as in the histories of Matthew Paris, and later in the Norman-French form of mesles, as in the Acts of Parliament of Edward I. and in the ‘Vision of Piers the Ploughman.’ In the 15th century the leper-houses in the suburbs of London were called the “lazarcotes” or “meselcotes.”

Gaddesden, by some unaccountable stretch of similarity, coupled the sores or tubercular nodules on the legs of “pauperes vel consumptivi,” who were called “anglicé mesles,” with the spotted rash of the Arabian “morbilli”; and it was doubtless this haphazard bracketting of two unlike diseases that led in course of time to the name of mesles being disjoined from its original sense of the leprous and restricted to the second member of Gaddesden’s strangely assorted couple. In the time of Henry VIII. smallpox and mezils are familiarly named together just as variolae et morbilli are an inseparable pair in the treatises of the Arabistic writers. A still more singular usurpation by “mezils” or “maysilles” or “measles” is met with in the Elizabethan period. In the vocabulary of Levins, a schoolmaster who was also a medical graduate of Oxford, the word variolae is rendered by “ye maysilles,” while morbilli is omitted altogether among the Latin names and smallpox among the English; and in the English translation of Latin aphorisms appended to one of the works of William Clowes, surgeon to St Bartholomew’s Hospital, variolae is in like manner translated “measles” on every occasion. In the English dictionary by Baret, belonging to the same period, measles is defined as “a disease with many reddish spottes or speckles in the face and bodie, much like freckles in colour”—which seems to exclude the possibility of a pustular disease having been part of the Elizabethan notion of measles.

Notwithstanding this singular usage of the vocabularies and dictionaries, the name of smallpox occurs by itself in letters or other memorials of the Elizabethan period, having been doubtless correctly applied to the true pustular variola. In the short essay on smallpox by Kellwaye, appended to his book on the plague (1593), measles and smallpox are distinguished on the whole clearly, according to the definitions of Fracastori or other foreign writers of the 16th century. The association between measles and smallpox that survived longest was a peculiar and somewhat uncommon one; certain cases of smallpox, in which the pustules were wholly or partially represented by, or changed into, broad spots level with the skin, red or livid in colour, and in which haemorrhages occurred from the nose, lungs, bowels or kidneys, that is to say, cases of haemorrhagic smallpox, were apt to be called, from the time of James I. until as late as the case of Queen Mary in 1694, by the name of “smallpox and measles mingled.”

From the date of the annual bills of mortality by the Parish Clerks of London, the year 1629, it is improbable that there was any real confusion between smallpox and measles; there was certainly some ambiguity in the entry of measles long after, but that later confusion, especially in the second half of the 18th century, was with scarlatina[1184]. The entry of measles is in the bills from the first, apart from that of “flox and smallpox:”

Year	Measles deaths	Smallpox deaths
1629	42	72
1630	2	40
1631	3	58
1632	80	531
1633	21	72
1634	33	1354
1635	27	293
1636	12	127
1647	5	139
1648	92	401
1649	3	1190
1650	33	184
1651	33	525
1652	62	1279
1653	8	139
1654	52	832
1655	11	1294
1656	153	823
1657	15	835
1658	80	409
1659	6	1523
1660	74	354

In the great epidemic of smallpox in 1628, the year before the bills begin, Thomas Alured wrote to Sir John Coke that his house in London had been visited “once with the measles and twice with the smallpox, though I thank God we are now free; and I know not how many households have run the same hazard[1185].” In the year 1656, which has the highest total in the above table, two cases of measles are mentioned in a letter of 31st May: “Young Sir Charles Sedley is at this time very sick of a feaver and the meazells, of which Sir William dyed”—Charles Sedley being then in his seventeenth year[1186]. An instance parallel to that of 1628, of measles and smallpox co-existing in the same household, occurred in the royal palace at Whitehall in December, 1660. The princess of Orange, sister of the king, died of smallpox on the 23rd; on that day, or a day or two before, her sister the princess Henrietta, who had come from France on a visit with the queen-mother, Henrietta Maria, removed from Whitehall to St James’s, “for fear of infection.” After a few days she embarked on board the ‘London’ at Portsmouth to return to France, but the ship had to come to anchor again owing to the princess being attacked with “the measles.” Her illness, which delayed the sailing of the vessel until the 24th of January, 1661, is uniformly spoken of as the measles in the various letters which make mention of it[1187]. In that year, and in several of the next ten years, the measles deaths in London reached a considerable total:

Year		Measles deaths
1661		188
1662		20
1663		42
1664		311
1665		7
1666		3
1667		83
1668		200
1669		15
1670		295

The epidemic of 1670 is the subject of a description by Sydenham, the diagnostic points of which were doubtless those current at the time.