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by water. Endeavour has been made to learn the water supply of the house in each case of enteric fever,
to which the notification certificates relate. In this work difficulty has in a limited number of cases
been experienced, especially where the house invaded is situated in a street supplied by two water
companies. I am satisfied however that any error due to this cause is so small that it does not
disturb the general indication of the figures.
Inasmuch as curves have been prepared to show the behaviour of enteric fever in London and
other communities, I have thought it well that similar diagrams should be prepared to show the
behaviour of the disease in the populations supplied by the several water companies, and Diagram II.
has been prepared with this object. It must be stated that when the number of cases is small the
method of exhibiting increase and decrease, as percentage above and below a mean, is open to objection,
but the general correspondence between the curves in Diagram II. leads me to the conclusion that their
indications are sufficiently trustworthy for the purpose I have in view. They suffice to show a correspondence
in the behaviour of the disease, i.e., increase of prevalence in the three weeks under
consideration in the populations supplied by all the water companies except the East London and the
Kent Companies.
In view of this exceptional behaviour of enteric fever in the later weeks of 1894, it is necessary
to consider whether any special circumstance may have led to failure of filtration of the water
supplied to London at some time which corresponds with that at which such failure might be expected
to manifest itself by increased prevalence of enteric fever. Diagrams III. and IV. show the condition of the
Thames and Lee as to flood at Teddington Weir and Fielde's Weir respectively during three years 1892-4,
the number of gallons of water passing over these weirs in each week being stated as a percentage above
and below the mean, and it will be seen by reference to these diagrams that notable floods occurred at
a time, antecedent to the weeks of prevalence of enteric fever, at which some new factor in the dissemination
of the disease might be expected to have come into operation in London. In order to ascertain
the effects of these floods on the waters supplied to the consumers, Diagram V. has been prepared.
This diagram is based upon the reports of the chemists who analyse the water for the London water
companies, and shows the close correspondence between the condition of the rivers and the quality
of the water which is supplied after filtration as regards organic impurity.*
It is important to ascertain whether the same behaviour of the disease is observable in the
populations supplied from the Thames and Lee outside London. To follow such increase to the
population supplied by the London water companies outside the County of London is more difficult,
because, although I am favoured by the Local Government Board with a return showing the number
of cases of enteric fever notified each week in many communities, this return does not cover the whole
of the area which has to be taken into consideration. I have, therefore, to supplement the return of
the Local Government Board, sought the aid of the medical officers of health of other districts in
which there is notification of infectious diseases, and I am able, through the courtesy of those who
have responded to my request, to state that when these districts are grouped, the same exceptional
behaviour of disease in the 49th, 50th and 51st weeks is observable in the group of districts in the
neighbourhood of London supplied by the London companies drawing water from the Thames and Lee,
whereas it is wanting in the group of districts otherwise supplied, concerning which I have received
information. (See Table III.) I might mention, however, with regard to the latter districts, that
there is considerable difficulty in obtaining a population in the vicinity of London sufficiently large to
give reliable figures for comparative purposes, as, generally, the more thickly populated districts in]the
vicinity of London are more or less supplied by the London water companies drawing from the Thames
and Lee.
It is necessary to consider what other circumstances may have given rise to this increase
of enteric fever in London and the surrounding neighbourhood. In this connection the distribution
of an infected milk supply deserves reference, for the milk of a single farm may in a few days be
distributed in many districts. A hypothesis of milk infection would not suffice to explain a practically
simultaneous increase of disease over so wide an area as that involved, although the effects of distribution
of a polluted milk supply, as in the case of a polluted water supply, are otten manifested beyond
the area of distribution of the supply. More recently the possibility of dissemination of enteric fever
by oysters has excited attention. Our knowledge of this subject is as yet very small, but it does not
appear that this hypothesis would afford adequate explanation of the circumstances observed.
Subject to what has already been said as to the fewness of the number of years of notification
upon which these observations are based, the hypothesis of water-borne contagion appears better able
to afford explanation of the increase of disease in the weeks in question. The absence of the evidence
of this increase in the London population of the East London Company no doubt needs explanation,
and it is to be regretted that in the absence of information as to the operations of the water companies
I am unable now to discuss this further ; but apart from this exception there appears to be a difference
in the behaviour of the disease in the area supplied with Thames and Lee water by the London companies
and in the area otherwise supplied ; and there is further the fact that very exceptional floods occurred
in these rivers at a time which corresponds with that at which some new factor in the causation of
enteric fever might be expected to have come into operation. These circumstances, I submit, indicate
the need for watchfulness over the distribution of enteric fever in London in its relation to water supply.
SHIRLEY F. MURPHY,
Medical Officer of Health.
* The diagram does not show a curve relating to the Chelsea Company's water for the reason that the
report of the metropolitan water examiner of the 9th of August, 1894, contains a statement to the effect that
the water previously taken for the purpose of analysis of that company's Water had been drawn, through error,
from a standpipe supplied from the New River Company's main.