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9
The epidemic
constitution
of 1917.
myelitis should be made upon blue forms and all reports relating to cerebro-spinal fever upon white
forms. Peace reigned under this dispensation until early in the present year, when it was found that
the "well-known varied and inconsistent character" of the epidemic disease, recognised 250 years ago
by Sydenham, was being yet again exhibited, and now the places both of cerebrospinal meningitis and
of acute poliomyelitis were being usurped by a closely related polioencephalitis, for the recording of
cases of which a new form distinct from the blue and white forms became necessary.
Brief reference to this new variety of epidemic disease, which curiously enough, was at first
confused with " botulism " will be made later. But first it is necessary to consider the epidemic constitution
of the early part of 1917. In previous annual reports statistical evidence to the effect that
cases of cerebrospinal fever and cases of influenza were associated one with another to a greater extent
than mere chance could explain, has been adduced. In a paper on " The Epidemiology of Cerebrospinal
Fever " (Proc. of the Roy. Soc. Med. Vol. X.) the time relationships of prevalences of pandemic influenza
and prevalences of cerebrospinal fever were set out, and examination was made of the hypothesis
that cerebrospinal fever must be regarded as "a complication or sequela of influenza, it being
assumed that owing to special circumstances some individuals, when attacked by influenza, develop
cerebrospinal fever." Shortly after this paper appeared it was ascertained that an important epidemiological
enquiry had been conducted during the preceding two years, the outcome of which was the
demonstration of the occurrence in association with cases of cerebrospinal fever of abortive forms of
illness described as influenza, pneumonia, catarrh, etc. The report on the results of this enquiry has not
yet been published, and it is therefore only possible to say here that it proves the existence between
cerebrospinal fever and so-called influenza of a relationship similar to that shown by Brorstrom to
obtain between acute poliomyelitis and influenza.
It may be added that reports of 1917 from bacteriologists of the Medical Research Committee
and of the Local Government Board reveal some divergences of view, the one school places reliance mainly
upon serological, the other exclusively upon cultural tests ; and from this there now emerges a disposition
to approach the epidemiological standpoint and to invoke the doctrine of " temporarily
• enhanced virulence," due to " the action of some unknown influence, telluric, climatic, or other,
which becomes operative under conditions of which we remain ignorant."
There is thus an approximation to the attitude of those who hold that the meningococcus is not
the causal organism of cerebrospinal fever, although it may assume importance as a secondary invader
when activated by some "unknown influence" temporarily endowing it with virulence. This view,
which has always been urged in these annual reports, has at least the merit of being reconcilable with
field observations. The hypothesis is examined further elsewhere (Vol. X. Proc. Roy. Soc. Med).
It is urged, in brief, that the reaction between the epidemic influence and the individual attacked, may
vary at diflierent phases of major waves of prevalence ; and that the epidemic form of cerebrospinal fever
represents the particular type assumed in " trailing epidemics " of influenza, in those members of the
community who have not acquired any sort of protection at a previous date.
The bearing of (he foregoing argument and its application to the now {May, 1918) prevailing type oj
epidemic influence.
Influenza, epidemiologically speaking, has always had three striking characteristics.
(i.) its " posting character " involving large areas of the inhabited globe and prevailing
in each affected community for some three or four months ;
(ii.) its power of impressing the mind of observers as being a "new disease."
(iii.) its ''protean manifestations."
These three characteristics are to be preferred in making the epidemiological diagnosis to indications
such as the presence in particular cases of sweats, or primary and secondary rashes, or even
of Kernig's or Babinsky's signs.
After a main epidemic or pandemic outbreak of influenza, in the explosive violence of which
nearly the entire community is affected, and in which symptoms of involvement of the cerebrospinal
nervous system are apt, as Dr. Bezley Thome pointed out, to predominate, the outbreak may settle
down, particularly in large urban communities, and become endemic, affecting then mainly specially
susceptible individuals. In them the prevalence may assume, particularly in cold countries, the
respiratory type—"the mistborn spectre" type—so common in the early nineties in Northern Europe,
or, on the other hand, gastro-intestinal outbreaks may occasionally be observed, or gastro-intestinal
symptoms maybe encountered in individual instances among groups of persons attacked by the disease
in one of its more usual forms ; or again, cerebrospinal meningitis, poliomyelitis, polioencephalitis,
or other manifestations of involvement of the central nervous system may present themselves.
The habitual sufferer from recurring attacks learns to appreciate the protean character of the
disease affecting him, according as one or other type prevails, or as one or other locus minoris resistentiae
is involved ; he may present in one attack a pharyngeal catarrh, or an otalgia, a catarrh of some other
mucous surface, a myalgia (stiff neck, lumbago, sciatica) or, again, herpetic or other eruptions; but
while the system of such sufferers is invaded in the outworks, so to speak, the patients seem to enjoy
a kind of protection of vital organs against the more severe manifestations of influenza.
After 15 or 20 years the prevalence again becomes widespread, and it is possible now, in the light
of study of the intervening " trailing epidemics " and of some knowledge of epidemiologyf to recognise
the cloven hoof. Thus, the sweating sicknesses of the middle ages, the dengue of the tropics, the cerebritis,
encephalitis, brain fever, etc., outbreaks of the older records, are all extraordinarily true to one
or other type of influenza, and all manifest the three main characteristics above described.
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