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intermediate period was marked—it was in this period that the Holborn and Southwark groups
occurred—and partly on account of this tendency to grouping these cases have been more particularly
studied by Dr. Hamer. The first period presented groups of cases, but inquiry was not
made as to these when they occurred, and difficulty was experienced in following the matter up
after an interval of time. The third period, in which the increase (as, indeed, was the increase
in the first period) was quite small, did not present marked grouping of cases.
The abnormal incidence of enteric fever in the intermediate period examined was in part
accounted for by the Holborn and Southwark groups already mentioned, and by groups in Stepney
and Poplar, but an important contribution to the increase was furnished by South-West London
as a whole, though more particularly by the portion of that area supplied by the Southwark and
Vauxhall Water Company. In the absence of other explanation it has, therefore, been necessary
to consider alternative hypotheses—one of water-borne infection, the other of infection by fish,
as accounting for the exceptional incidence of the disease.
Dr. Hamer discusses the topographical distribution of the cases and the time relations
between the occurrence of flood in the river Thames and the exceptional prevalence of enteric
fever in South-West London, and he points out that there are difficulties in the way of accepting
the first hypothesis. An infected fish hypothesis, on the other hand, he finds, is consistent with
the known facts as to exceptional prevalence of enteric fever in various parts of London in the
intermediate period (43rd-49th weeks) of 1903, and no other adequate explanation of this prevalence
is forthcoming. If this hypothesis be well founded it becomes a matter of interest to ascertain
whether there is reason for suspecting infected fish has produced mischief in the past, for it
is clear that if this cause were widely operative at the close of 1903, when indications of its
existence were so little apparent save in two localities (Holborn and Southwark), it may readily
have been a source of infection on numerous previous occasions without exciting notice.
The three outbreaks attributed to consumption of fish in 1900 and in less degree those of
1903, were characterised by two features, both frequently met with in outbreaks due to food, to
which Dr. Hamer directs special attention—the occurrence of multiple attacks in houses, and
abnormality of age-incidence of the disease, persons at the ages 3-25 inclusive being attacked with
special frequency. Examination of the notifications of enteric fever in the areas involved in these
outbreaks showed that there were not wanting indications suggestive of the existence of the
characteristic features in question at other times during the years 1896-1903 in these areas. This
has led Dr. Hamer to examine spot-maps showing the distribution of cases of enteric fever in 1899
and 1900, a period in which there was excess of enteric fever in London beyond the average of
recent years, and more particularly to study the notification records of further areas which enteric
fever especially affected in those years, and he finds that the cases in these areas also present in
greater or less degree the features above referred to, not only in 1899 and 1900, but also in other
years. A number of charts have thus been examined, and it transpired in each instance in which
these appearances were manifested that the further areas in question were occupied by poor persons
by whom fried fish was largely consumed. The secondary cases occurring in these areas were in each
instance distinguished (so far as it was possible to do this on the notification data which were for
this purpose alone available), and the evidence pointed less to communication of the disease from
person to person than to a common source of origin. The simultaneity of occurrence of an
abnormal number of cases in widely separated areas also suggests some food supply as being at
fault; while the abnormality of age-incidence, although possibly explicable on the ground of
character of the populations invaded, was specially marked, in particular instances examined,
at the times of the exceptional prevalences—a fact which is consistent with the food hypothesis.
It should be noted, moreover, that so far as there is information on the subject, the cases now in
question were not attributed at the time of their occurrence to any of the foods ordinarily credited
with ability to produce enteric fever.
The phenomena commonly met with in food outbreaks (occurrence of multiple cases and
abnormal age-incidence) were found by Dr. Hamer, in his inquiry, always associated with the
two conditions—poverty and fried fish eating, and it was impracticable, in the absence of precise
inquiry at the time, to demonstrate in the case of these further areas that this article of food as
apart from poverty stood in causal relationship with excessive fever prevalence; it was indeed
found impossible to discover an area in London in which the one set of circumstances existed apart
from the other. The appearances exhibited on the charts are sufficiently striking, however, to
make it desirable that the future behaviour of enteric fever in the particular areas should be
studied, and that henceforth attention should be directed to the possibility of fish acting from
time to time as an infecting agent.
Shirley F. Murphy,
Medical Officer of Health.