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15
This last-named conclusion is further confirmed by close study of the history
of diphtheria in some of the great towns of this country. The diagram on p. 16 exhibits
contours which illustrate the irregularity of the course of diphtheria mortality
in towns of England and Wales. The towns are arranged in geographical order,
and there is, it will be seen, some evidence of similarity in the contours in adjacent
towns, but practically little or none in the different divisions of England and Wales
represented in the diagram. The first contour relates to London, and shows prolonged
incidence in the nineties, followed by fifteen or sixteen years of low prevalence.
There is, it will be seen, a gradual increase from about 1912 up to 1921 and 1922,
but even in the latter year, although there was epidemic prevalence, the mortality
did not reach anything like the figures of the nineties. It will be noticed that most
of the periods of high mortality in other towns have occurred within the period
of London's high prevalence. Between 1890 and 1912, only Newcastle, Hudderfield,
Liverpool, Manchester, Derby and Nottingham can claim to have escaped
quite lightly.
Similar phenomena to those seen in these towns were commented upon by
Newsholme in his work on Diphtheria, in connection with his examination of the
time relations of epidemic prevalences in countries of Europe and America; they
have been illustrated, moreover, in the London annual reports, from time to time,
in relation with epidemic prevalences in the individual boroughs of the County of
London and also even in individual schools in particular boroughs. The impression
left on the mind is one of an eminently infectious disease, but of one which spreads
quite slowly from one area, town or country to another: so that, whereas in a period
of 4, 5 or more years a continent or large area as a whole may suffer severely, the
extent to which portions of such continent or other large area are involved varies
greatly within the series of years under review.
The study, therefore, of the time and space relationships of epidemics of
diphtheria and scarlet fever, while it brings into prominence the close relationship
existing between these epidemic diseases and the importance of certain conditions—
diminished rainfall, movement of population, operation of measures of isolation,
cleansing and disinfection—in favouring or limiting spread from case to case, at the
same time serves to focus attention upon the outstanding fact that widespread
epidemics of throat disease have shown a tendency to occur in Europe and
America at recurring intervals of some 20 or 30 years. Inasmuch as in the case of
scarlet fever one attack of the disease confers almost if not complete protection
against subsequent attack, and as in the case of diphtheria a large, if not so complete,
degree of protection is conferred upon each sufferer, it is naturally assumed that,
following upon one of the waves of widespread prevalence of throat malady, the
affected population might be expected to show comparative immunity, at any
rate for the time required to allow of the upgrowth of a new population susceptible
to attack.
Additional factors are however, doubtless, also operative. One of these may
be the influence of other forms of disease and particularly of epidemic diseases of
the influenzal group. It has been observed from time to time that widespread
influence upon throat epidemics has been exerted by epidemics of influenza. In
the annual reports for 1920 (p. 54) and for 1921 (p. 45) comment was made upon the
frequent occurrence of scarlatiniform rashes during an influenza outbreak and also
on the raised case-mortality of scarlet fever during the influenza epidemics of 1918-19.
This and the similar phenomenon in the influenza epidemic of 1922 are illustrated
in the inset to the diagram on p. 24 and (though in less marked degree) there are
also apparent there similar variations in the case-mortality of diphtheria. An
interesting observation which possibly may have a bearing upon the point now
under consideration is the fact noted by Dr. Middleton Hewat that in Fulham
the percentage of apparently erroneous notifications of diphtheria had increased
from 16.2 in 1923 to 24.3 in 1924.
11908 B2