London's Pulse: Medical Officer of Health reports 1848-1972

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Deptford 1911

Annual report on the health of the Metropolitan Borough of Deptford

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37
number of flies has not been as great as usual in London. It
is recognised by some that with rows of houses crowded as they
are into narrow streets, comparatively few flies are sufficient to
carry infection from one house to another. Although in 1911
we had only thousands of flies instead of tens of thousands,
there were quite sufficient to account, if necessary, for all the
cases of infantile diarrhoea which occurred.
Of course it is obvious that there are other sources of
infection, but we may take it that flies are the principal agents
in the spread of summer diarrhœa in young children. We are
absolutely dependent on outside sources for the supply of milk,
and it is readily conceivable that flies contaminate some of the
milk even before it arrives here, and this fly-infected milk may
then give rise to infantile diarrhœa in a district which itself is
comparatively free from flies. If warm weather conditions
prevail the growth of the bacteria in milk is favoured, and the
greater number there are of flies the greater likelihood there is
that unprotected milk will be contaminated. Luckily we have
taken special pains to do away with collections of manure and
house refuse which are the favourite breeding grounds of the
house fly.
If flies are present in noticeable numbers in a crowded
district it only needs the ignorance and carelessness of one
mother whose child has summer diarrhoea to cause a rapid
spread in the number of cases; the flies acting as carriers of
germs from the infective excreta, and infecting houses where
there is a free access of food.
Flies may therefore be a nuisance and injurious to health
by their mere numbers, or may also be a specific and dangerous
nuisance by being capable of carrying all sorts of disease germs.
A consumptive for instance who has not been instructed may
expectorate on to the ground or into an open vessel, flies settle
on it, ignest some of the tubercle bacilli, and then may