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Report of the Medical Officer of Health.
87
marked peculiarities ; thus, if the area surrounding the fried fish shop be divided into four quadrants—
north, south, east and west—the cases of typhoid fever will be seen to be almost entirely confined to
the eastern and southern quadrants. There was, in fact, only one case in the northern quadrant and
no case at all in the western quadrant. The escape of the western quadrant is readily explained when
it is noted that that quadrant has no ordinary resident population, being entirely covered by Post Office
buildings. A large staff occupies these buildings, but the men are catered for upon the premises, and
they do not as a rule purchase food at shops in the area. The escape of the northern quadrant with
only one case cannot, however, be similarly explained. It hence becomes clear that, if fish sold at
the fried fish shop were the cause of the special Finsbury prevalence, there must have been circumstances
associated with the distribution of the fish which caused differentiation as regards incidence of typhoid
fever upon the areas surrounding the shop. It was, of course, possible that only one particular batch
of fish was at fault. Examination showed, moreover, that there were certain special features with
regard to fish distribution, considered in relation to time and space, from the shop and these are
clearly deserving of detailed study.
(a) At the dinner hour every day some scores of persons who do not reside in Finsbury purchase
fish at the fried fish shop—the outbreak, on the other hand, was, with the few exceptions noted, confined
to the near neighbourhood of the shop. If fish were at fault it was unlikely to be fish consumed in the
middle of the day.
(b) The almost exclusive attack of sufferers at the ages included in the age group 5-25, points to
limitation of the operation of the cause of the outbreak to persons at these ages, and question, therefore,
arose as to whether at any time of day children and young adults constituted an exceptionally
large percentage of the purchasers.
(c) The topographical distribution of the cases already referred to raises questions as to the possible
existence of differentiating circumstances—for example, such as are associated with social status of the
people living in the various streets and courts surrounding the fish shop. Purchasers of fish might be,
so to speak, selected for attack by reason of their buying a special kind of fish, and paying a special
price for it. In this outbreak, as has already been found to be the case in fish-borne outbreaks of
typhoid fever occurring in 1900, 1903, 1908 and 1910, the history given by some of the sufferers clearly
directed suspicion to plaice, and in a few instances mention was especially made of the fact that a ½d.
of 1d. piece of his fish had been purchased, the sufferers giving such a history being as a rule young
children.
It was clear, therefore, if the infected fish had been distributed on one particular occasion only,
that the incidence of the resulting disease upon age, and upon localities enar the shop, would vary
considerably according to the time when the fish was sold. Suspicion was in this connection naturally
directed to the evening when frying first commenced, inasmuch as observation showed that at this
time the ages of the persons leaving the shop, and returning to houses in the area, were not greatly
different from the ages of the sufferers in the outbreak. Moreover, distribution of infected fish at this
time might conceivably explain the topographical distribution of the cases, for in certain obvious respects
the northern quadrant differed from the southern and eastern quadrants. It was decided, therefore,
to have precise observation made of the customers visiting the fried fish shop in the early hours of the
evening.
It may here be convenient to describe briefly the peculiarities of those portions of the area
surrounding the fried fish shop which are occupied by a resident population. In doing this Mr. Charles
Booth's scheme of classification of London populations will be used.*
The northern quadrant consists in part of houses fronting upon two main streets coloured for
the most part pink or red on Mr. Booth's colour scheme, and in part of a much poorer side street
(C, light blue) and a cul-de-sac (B, dark blue) opening out of the same, The eastern and southern
quadrants each contain large blocks of artizans' dwellings (D, purple). They also contain houses fronting
upon main streets (E, F, etc.), though not so large a proportion of the population lives in such houses
as is the case in the northern quadrant.
The population living in houses fronting upon main streets (E, F, etc.) has almost entirely
escaped attack. Leaving this better circumstanced population out of account, the eastern and southern
quadrants contain large blocks of artisans' dwellings (D, purple); and certain streets and courts (B,
and C, light blue and dark blue, or even black) cover the remaining portion of these quadrants,
The persons in these two quadrants belonging to classes C and D have specially suffered from typhoid
fever. Examination of the topographical distribution of the suffering population shows that if the
cause producing typhoid fever in the area had been one which operated more especially upon persons
of the classes C and D, then the distribution of cases in that area would necessarily have closely
approximated to the distribution actually observed in this outbreak. On such an assumption the
heavy incidence of the disease upon the eastern and southern quadrants at once finds explanation.
Before illustrating this in detail it is desirable, however, to allude to the question of age-incidence.
The peculiar age-incidence in this outbreak has been already referred to. On "Wednesday,
11th October, observation was kept upon all persons coming out of the fried fish shop between
* Mr. Booth's scheme of classification, beginning from below, included A, black—lowest class, vicious, semicriminal;
B, dark blue, very poor, casual, chronic want; C, light blue, poor, 18s. to 21s. a week for a moderate family;
D,purple, mixed, some comfortable, others poor; and so upwards to E, F, G and H, pink, red and yellow, the more
well-to-do populations. Previous experience in London has shown that fried fish outbreaks do not, on the one
hand, as a rule implicate the pink, red and yellow streets, and on the other hand only slightly implicate the black and
dark blue streets. It is the intermediate social class which especially suffers. Light blue and purple (C and D)
dominate the areas implicated in fried fish outbreaks (see Annual Report, Medical Officer of Health, County of London,
1903).