View report page

83 Annual Report of the London County Council, 1911.
6.30 p.m. and 8.30 p.m. Of the total number leaving the shop (279) about half returned, during the
five or ten minutes during which they were watched, to houses within the area of the explosion; the
large majority of these parsons were under 20 years of age.* In fact, the age-distribution of the
customers who were traced to houses within the area was practically identical with that of the sufferers
from typhoid fever. The p3culiar age-incidence observed in this outbreak, it may now be noted,
very closely resembled that obtaining in the original fried fish outbreak of 1900, and in correspondence
with this the ages of the persons who on leaving the Finsbury shop returned to houses in the area,
in 1911, were practically identical with those of the population studied 11 years before in Southwark
(Annual Report, Medical Officer of Health, 1900.)†
A precise test can now be made as to the sufficiency of an hypothesis that the cheaper portions
of fried fish sold to the early evening customers on a particular evening in August were responsible for
this outbreak. It may be safely assumed that the children and young adults would buy the cheaper
portions of fish, and hence, if the destinations of the persons, say between 5 and 20 years of age, who left
the shop between 6.30 and 8.30 p.m., and who were traced to their homes in the area, be plotted out
upon a map, the distribution of these cases should correspond with that of the sufferers from typhoid
fever. It will be seen on referring to the two maps that the correspondence is remarkably close;
and the fact is even more important when the marked asymmetry of the distribution of the sufferers
from typhoid fever and their exceptional age-distribution is borne in mind.
On the lower map certain houses to which a customer was traced are indicated, and
further an "o" represents customers who can be assigned to a paticular area or street but whose
precise home cannot be specified. Seventy customers in all were thus traced (see Diagram). On the
corresponding upper map are shown the houses in which 56 sufferers from typhoid fever lived. Study
of the two maps reveals the close similarity of the two distributions. The closeness of this correspondence
may be further illustrated by dividing up the area (within the circle of 440 feet radius described
around the chosen centre) into five areas with, roughly speaking, equal populations of some six or eight
hundred persons each.

It will be seen that area IV. has over 40 per cent, of both customers and sufferers; area V. has
approximately 30 per cent, in both categories; in area II. the percentage is 12 in each,
and in areas I. and III. neither the customers nor the sufferers exceed 10 per cent. The chances against
such correspondence being the result of mere coincidence must be very great.
These two lines of enquiry therefore, topographical distribution and age-distribution, considered
separately and in conjunction, yield strong confirmatory evidence in favour of the fried fish hypothesis.
The third line of enquiry has concern with the distribution of attacks in families and among single sufferers.
An analysis of 52 cases shows that there were 29 sufferers who were the only members of their
families attacked, there were eight families with 2 cases each, one family with 3, and one with 5.
Of the 29 single sufferers all except one may have bought their fried fish independently of other
members of the family to which they belonged. Six of the pairs of sufferers had bought fish conjointly
but independently of any other members of their families. In the family with 5 sufferers, 4
had habitually eaten their fried fish together, the fifth had eaten fish from the same source, but not
on the same occasion as the other 4. This last case was in all probability not a case of typhoid
fever. The intervals of time between successive attacks in each house can be studied in the appended
table. (See "Remarks" column as to the relationship of cases in family groups.) These intervals varied
from a day or two to as long, in one instance, as twelve days. In striking contrast with multiple
attacks in fried fish eating families stand the histories in cases 21 and 29 with regard to ice cream.
Both sufferers were members of ice cream eating families and in each family only one member suffered.
It should be mentioned that coincidently with the Finsbury outbreak two groups of cases of
typhoid fever occurred in other parts of London. Five cases belonged to St. Pancras and five to
Lewisham. In each borough the sufferers had been supplied with fish from a particular shop, one shop
being in St. Pancras and one in Lewisham. The attempt was made to trace the source of supply of the
fish to the Finsbury, St. Pancras and Lewisham shops, but no community of supply was established.
Judging from the dates of onset of illness in the sufferers the indications point in all three boroughs
* Persons who did not return to houses in the area include a few who went into public houses, some dozen
who went into a picture palace, upwards of a hundred who walked away from the area (whether to return to it or
not cannot be stated) a cabman who drove away, and one or two persons who mounted upon tramcars. The persons
who did not immediately return to houses within the area included a much larger proportion of adults and correspondingly
fewer children than did the persons who were seen to return to houses within the area.
†The age distribution of the Finsbury customers, as a whole, did not correspond quite so closely with that
of the Southwark customers. The Finsbury shop clearly supplied a number of persons who lived at some distance from
it, and these persons were as a rule older than were the customers who returned to houses in the area.