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If then to the 190,000 persons in the 35 areas, addition be made, of say, 310,000
persons, representing a further sample of persons belonging to social classes Cand D,
it may be inferred that some half-million persons in London (the poorer moiety
of the whole 900,000 persons in classes C and D, representing the principal aggregations
in London of any considerable number of persons belonging to these classes)
yield practically the whole of the excess number of cases which go to constitute
the successive autumnal prevalences.
A further point must be noted. The diagram in the Annual Report of 1903
shows that in the 24 areas, during the times of special prevalence of typhoid, two
striking phenomena make their appearance. In the first place, multiple attacks
in houses become common; and, secondly, a special age-incidence of the disease
is manifested, children and young adults being more than usually numerous among
the sufferers. Where these phenomena occur a note is made in the accompanying
table that "grouping of cases" was manifested. In almost every instance this
grouping is found to have been accompanied by multiple attacks and by the special
age-incidence.
If it be assumed that infected food was sold from time to time to the populations
included in the half million persons above referred to, throughout the nineties and
in the early years of the present century, that the sale of such food was especially
common about the latter part of August or in September or early October in those
years, and that these supplies were gradually restricted during the early years of this
century, were discontinued in 1909, and (after reintroduction on a small scale in
1910 and 1911) from 1912 onwards, there is afforded a fairly complete explanation
of the decline of typhoid fever as a whole, of the diminution in the extent
of the autumnal rise, and of its complete absence in 1909 and from 1912 onwards.
(b) Detailed study of the larger local prevalences of typhoid fever (1891-1922)
in London boroughs, shows that coincidently with a large prevalence in one borough
there has been a marked tendency for one or more smaller prevalences (showing the
phenomena of multiple attacks and of special age-incidence) to affect other boroughs.
Moreover, the locus in quo concerned in many of these prevalences is found again
and again to be one or other of the 35 areas already alluded to, or failing them,
some other area occupied mainly by persons belonging to classes C and D. Further,
it is occasionally found that outbreaks affecting institutions are developed at the
times when larger or smaller prevalences involve populations of the classes C and D
living in various parts of London. Finally, localities occupied by classes C and D
of the London population, and sometimes institutions also, are found occasionally
to be affected by small prevalences of typhoid at other times of the year than the
37th-48th weeks.
These phenomena may be examined in detail by study of the Diagram and
Table. They convey, in the gross, an impression of the occasional interposition at
various times of the year, and of the frequent appearance during the 37th-48th
weeks in successive years, of some special influence favouring spread of typhoid fever
in London.
(c) One of the influences, and, indeed, the main one promoting spread of typhoid
has been fish, which has been definitely incriminated in more than a dozen considerable
prevalences of typhoid fever in London or its neighbourhood. (These fish outbreaks
are noted in the Observations column of the accompanying table, they are also
described on pp. 13 to 15 of the Annual Report for 1919, and references are there
The 11 additional areas are:—
i. Brixton, Lambeth 8.000
ii. Upper Holloway, Islington 8,000
iii. Caledonian-road, Islington 7,000
iv. Pophm-road, Islington 4,000
v. Nile-street, Shoreditch 6,000
vi. Hoxton-street, Shoreditch 4,000
vii. Finsbury 6,000
viii. Stoke Newington 5,000
ix. Dalston, Hackney 6,000
x. London Fields, Hackney 5,000
xi. Upper Clapton, Hackney 5,000
64,000