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(iii.) From about 1909 onwards the cases of " typhoid fever " developing in
London, apart from persons infected outside London, have in the majority of cases
been deemed on further examination not to be typhoid fever.
In the light of the foregoing considerations and of the analysis made in last
year's annual report of the causation of London typhoid during the last 50 years,
attention has been devoted to comparing and contrasting the behaviour of the
disease in the County of London with that in other counties in England and Wales,
Study of London typhoid, outside and inside the mental hospitals, during the
last 30 years suggests that there are, epidemiologically speaking, two kinds of epidemic
disease commonly so diagnosed. There is the typhoid caused by eating polluted
fish or shellfish, which makes up the bulk of the typhoid in the outside population ;
it is unassociated with dysentery, it may occur in explosive outbreaks, it exhibits no
tendency to spread from case to case, it shows increase in the autumn, preferentially
attacks males and the ages 10—25, and when caused by fish or shellfish other than
oysters is mainly limited to persons belonging to Charles Booth's classes C and D.
Then, secondly,there is the typhoid of the type sometimes met with in mental hospitals,
which is associated with dysentery, does not occur in explosive prevalences, apparently
spreads from case to case, shows no marked autumnal increase, preferentially
attacks females and not infrequently persons over 25, and has no such marked
special incidence upon a particular social class as in the first mentioned type. The
fact that there is a distinction between these two typhoids has been rendered
particularly apparent during recent years, owing to the almost complete disappearance
of the first.named type. Comparison between the typhoid fever of London and that of Ebgland and Wales.
In the fight of these considerations pre-conceived notions concerning the
reasons determining the contrasts presented by typhoid fever incidence in London
and in other parts of this country must be reviewed. First, it may be noted,
that the special features observed in the predominant type of typhoid occurring
in London can be traced back with complete confidence for 30 or 40 years. It
may be that before that time London, like other places, suffered severely from
typhoid of the second type, such as may occur nowadays in the tropics, or may be
associated with wars and with dysentery, which may affect country districts as much
as or even in preference to the towns, may be contagious from case to case and prove
to be a disease to which strangers and new arrivals are especially subject, thus giving
rise to the view that a kind of acclimatisation occurs. All these features have,
of course, been wanting in the main mass of London typhoid of the last 30
years.
On the other hand, it must be borne in mind that typhoid fever nowadays is
found to be very elusive—witness the Asylums Board's Returns of" wrong diagnosis "
—what, then, must have been the difficulties more than 30 years ago ? There is,
of course, the possibility that the anomalous features at one time presented by
" typhoid " must be attributed to the fact that many different forms of illness were
so designated. In this quandary it seemed worth while to focus attention upon the
London predominant type of the last thirty-five years, the typhoid which has been
found to be associated with consumption of polluted shellfish and fish. If attention
be concentrated upon the salient characters observable in this type of typhoid it
can be held up as a standard by which to test the typhoid of the rest of England and
Wales. Now the London typhoid affected almost exclusively a particular social class.
Turning, therefore, to the other counties of England and Wales, question arises
whether any similar phenomenon can there be discerned ? Study of the figures,
decade by decade, shows very marked excessive incidence of typhoid fever upon
mining and industrial areas; in fact upon populations very similar to those which in
the past have consumed the kind of shellfish or fish found to be at fault in London.
The incidence upon the counties of England and Wales may be examined in detail
with the aid of the accompanying maps.
In the decade 1871-80, a rate of over 300 per million was attained in four areas—