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34
in 1910, the number of notifications was the smallest recorded up to that date, some 10,SCO; in 1916,
however, only 8,778 cases (excluding military cases) were notified; the total for 1917 was lower still,
only just over 6,000 cases of scarlet fever; there were, however, nearly 8,600 cases of diphtheria.
The relation of flea prevalence to that of scarlet fever has been commented upon from time to
time in these reports. There was an increase in flea prevalence in 1913 and 1914, corresponding with
the culmination of the major wave of scarlet fever, and since then there has been diminution. (See
Diagram).
The reasons, so far as they were then appreciated, for claiming that a flea hypothesis of causation
of scarlet fever should be carefully examined were first set out tentatively in 1908, and a first "flea
curve," based on examination of common lodging.house beds, was obtained in 1909 and published
in the following year (Appendix IV., Ann. Rep. Med. Off., 1910). The close correspondence in the
seasonal curves of scarlet fever and of flea prevalence was thus made apparent, and the important fact
that maximum flea prevalence antedates maximum prevalence of scarlet fever was revealed. In the
annual report for 1911 the seasonal curves of 3 years were exhibited, and the need for further study
of"the special incidence upon children, and particularly upon children in schools, and the evidence
as to fomites and the alleged clinging of infection to houses or rooms, or in schools to particular departments
or even classrooms," was considered. Moreover, reference was made to the need for closer
examination of the return case problem.
The first of these two lines of enquiry was taken up in 1912, and Diagram C, Annual Report for
1912, illustrates the tenacity of hold of scarlet fever and diphtheria upon particular elementary schools.
As noted originally by Dr. Niven, the phenomenon suggests the clinging of infective property to the
premises rather than to the children, and the possible influence of dust was hinted at by him in this
connection. In 1913 the curve of seasonal prevalence of fleas was established upon a more satisfactory
basis "by the inclusion of material made available by the examination of elementary school children,"
a more satisfactory test than that previously afforded by examination of common lodging.house beds.
The curves for 5 years, including the children's curve for 1913, are given in the Annual Report for 1913,
find in 1914 the curves for 6 years were shown; the fact was now clearly demonstrated that the maxima
for scarlet fever always "lagged somewhat (three or four weeks) behind those for flea prevalence."
The subject of "school influence" was, in 1914, further studied (see D iagram E., Ann. Rep.
Med. Off.), and it was made clear"that some condition, closely associated with poverty, determines an
earlier incidence of scarlet fever in the poorest areas," and that "when, moreover, children attended
elementary schools some condition (presumably the same condition) exerts its influence and determines
in even higher incidence of scarlet fever upon the comparatively unprotected'less poor than upon the
partially protected'poorest'children."It was added that" it is quite possible that one of the factors
sperating in the schools is the presence of vermin, and this is true despite the fact that the evidence of
scarlet fever at school ages is appreciably less in schools where the children are badly than in those where
they are less badly flea bitten."
The seasonal curves obtained year by year have continued to reveal the phenomenon of ante.
lating of the disease maximum by the flea prevalence maximum, and this fact has been illustrated
n successive Annual Reports (see also the composite curve, inset in upper Diagram facing page 35).
In the Annual Report for 1915 reference was made to the influence of cycles of dry years upon
cycles of scarlet fever prevalence, and also to the respective "geographical ranges" of the flea and of
scarlet fever; and in the Annual Report for 1916 the close epidemiological relationships between scarlet
fever and diphtheria were referred to, the extent to which variations in nomenclature had confused
the issues was noted, and in this connection closer study was made of the distribution of diphtheria
and scarlet fever in various parts of the country during the past seventy years. There can, of course, be
no question that the marked decline, during that period, of scarlet fever has been accompanied by greatly
increased attention to the importance of cleanliness and disinfection, and also by decline in prevalence
of fleas. The relation of variations in flea prevalence to the recent major waves of throat illness, which
culminated in 1907 and in 1914, was also considered. The Diagram illustrates the fact that the corre.
pondence between the figures for flea prevalence and for scarlet fever is closer when the common lodging.
louse population is used as an index to flea prevalence than it is when school children are so used. This
nay be in part due to special war conditions.
During the past year the attempt has been made to examine further the altered behaviour of
scarlet fever in recent times, and special study has been made of the "return case problem." This
question is one which has been much studied during the last 20 years. The large mortality caused
luring the major waves of scarlet fever in the sixties and seventies had been followed by very notable
Jecline throughout the eighties and nineties, and a still lower level has been attained during the present
century. This. very satisfactory condition of things was not unnaturally attributed to the influence
of isolation hospitals, but it was noted, just before the close of last century, that although the mortality
Erom the disease had so appreciably diminished there was some ground for thinking its prevalence had
been maintained. Inquiry with regard to this subject was greatly stimulated by a report by Dr. J. T.
Wilson, who pointed out that the decline of mortality was not confined to the larger towns, which had
led the way in active prevention, but was shared by other towns and by rural areas. He argued,
therefore, that it was "to be feared that the prophylactic value of isolation is by some authorities overrated."Upon
this it may be observed that Dr. Wilson's enquiry, which related to Scotland, clearly
showed that the decline was, as a matter of fact, manifested in the larger urban communities shortly
prior to its appearance in the smaller town and rural districts. Moreover, even if the "prophylactic
value" against attack by scarlet fever might conceivably be held to be open to some question, there
could remain no doubt whatever as to the correspondence in time between growth of hospital isolation
and the marked decline of severity of attack.
History of
the enquiries
made in
London with
regard to the
flea hypothesis
of
causation of
scarlet fever.
Hospital
isolation and
the decline of
scarlet fever.