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The lesson to be drawn is one which has been again and again pointed out by writers on epidemics,
namely, that prevalences of throat illness should be studied as a whole; regard must not exclusively be
paid to scarlet fever on the one hand, or to diphtheria on the other. As long ago as the eighteenth
century, there was much confusion with reference to epidemic throat disease. It was not until 1831 that
the term "diphtheria" was employed; up to 1855, diphtheria and scarlet fever were still classed together
by the Registrar-General; and in German statistical returns, the heading "Scharlachdiphtherie"
has continued in use up to the present time. The discovery of the diphtheria bacillus by Klebs and
Loeffler, in 1883 and 1884, led to the adoption of bacteriological methods for confirmation of the diagnosis
of diphtheria, and probably in large degree as a result of this, there has been increasing use of the term
"diphtheria" during the last 30 years; such altered practice as regards nomenclature has apparently
been especially followed in London and some other large towns.
Epidemiological
relationship
of these
diseases.
It is important, therefore, to note that facts with regard to these diseases, which had been brought
clearly to view during the eighteenth and the first three-quarters of the nineteenth century, have been
rather thrown into the shade as the result of the bacteriological investigations of the last 20 or 30 years;
in the first place, there are the remarkable relationships, in times of prevalence and in area of distribution,
between scarlet fever and diphtheria ; then again, there are important climatic relationships. It must,
moreover, be realised that epidemic throat affections manifest variations of type and tend to approximate
more closely to, or to diverge from, one another, during periods of widespread or of limited diffusion,
as compared with other times. If the prevalences of diphtheria during the last 50 or 60 years be studied,
it will be seen that one great wave crest was developed at the close of the "fifties," and this was followed
by another almost comparable epidemic elevation in 1893; since that date, there has been descent into
a trough of low prevalence. Again, two similar "major waves" of scarlet fever culminated, the first
about 1859 and the second about 1893, the earlier being much the more formidable of the two. Upon
this greater movement, the wavelets of scarlet fever prevalence are seen much more clearly displayed
than is the case with the minor waves of diphtheria; the ripples of the former disease are mimicked,
speaking in a general way, by those of the latter, but there are exceptions—for there is nothing to
correspond to the scarlet fever ripple of 1869-70 in the diphtheria records.
Increasing
use of the
term diphtheria
in
death returns
It is noteworthy that two observers, Dr. Longstaff and Sir Arthur Newsholme, have exhaustively
analysed the relationship between dry years and one or both of these diseases. Dr. Longstaff found
the correspondence close in the sixties and early seventies, but less marked in later years. Sir Arthur
Newsholme, dealing with diphtheria alone, but collecting data from every civilised country, concludes
that the "essential factor in the production of epidemic, and still more of pandemic diphtheria,
is the occurrence of a succession of years of deficient rainfall, associated as they must be with
abnormally dry conditions of the soil and sub-soil." Careful examination of the work done in this
connection leads, it may be affirmed, to the conclusion that prevalence of both diphtheria and scarlet
fever is definitely favoured by the occurrence of a series of abnormally dry years.
Variations in
nomenclature.
The question of the influence of nomenclature was very carefully considered by the late
Dr. J. F. J. Sykes, in 1894; he emphasised the extent to which "alterations in classification"
and "variations in nomenclature" had confused the issues, and propounded the question "whether
the variations of nomenclature may not be due to a change of type in disease of the throat.' It may be
stated finally that the more the figures are studied, the more is the impression strengthened that varying
fashion, as regards nomenclature, has played a great part in connection with these two diseases; it
may, moreover, be taken as certain that at the crests of the major waves the epidemic type approximates
more nearly to what may perhaps be styled the diphtheritic, and between the crests to what may perhaps
be styled the scarlatinal type.
Geographical
distribution
of diphtheria
and scarlet
fever
Ihe peculiar geographical distribution of "diphtheria," demonstrated during the third quarter
of the last century by Dr. Longstaff, becomes perhaps more comprehensible when a broad view of the
phenomena is taken. Diphtheria was specially incident upon rural areas in the prevalence of 1859-60
rather less markedly so in the decade 1861-70, and again distinctly less so in 1871-80; since that decade
it has been held to be much more common in the towns. The disease prevailing in 1859, and in immediately
succeeding years, was one in which severe throat complication was particularly marked; and the recorded
prevalence of this disease in the rural areas was undoubtedly emphasised by the prominence given
at that time to the supposed invasion of this country, by the "Boulogne sore throat," and by
the attention thereupon concentrated upon the researches of Bretonneau with regard to diphtheria.
London had already passed through the worst of the outbreak before the altered nomenclature became
fashionable and before the rural areas were widely involved, and in Loudon for many years after 1859
there seems to have been a decidedly conservative tendency in the matter of describing epidemic throat
diseases.
In confirmation of this view, Mr. Netten Radcliffe's report may be cited. He stated that in London
"scarlet fever underwent a prodigious increase in 1858, and prevailed in that year to a greater extent
than in any previous year of the 19" (viz., 1840-59); again, he says, " the mortality from croup advanced
year by year from 1854"; and, he adds, "London was invaded by diphtheria already, in 1857." Finally,
Newsholme, summarising the evidence, concludes that " in London, diphtheria was steadily increasing
in amount from 1854 onwards, being widely epidemic early in 1857." Bearing all this in mind, and
remembering that major waves of scarlet fever, in the country as a whole, stand chronicled for 1840,
1848, 1852, and 1858, it seems clear that the generally described epidemic throat illness of 1859, really
corresponds to the fall of a wave of prevalence which had already swelled in 1854-57. The country
districts suffered, however, later than the towns, and perhaps on this account, the impression was created
that the disease now designated diphtheria was preferentially a rural disease. Longstaff states that
at that time " scarlet fever was believed to be the form assumed by epidemics in the towns, ar.d diphtheria
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