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16
DIARRHœA AND ENTERITIS
'MORTALITY PER 1,000 LIVE BIRTHS
Enteric fevers
Notification of fevers of the enteric group numbered 48, exactly the same as in
1947. There was only one death. Fifty years ago the mortality rate was 0.14
per 1,000 (600 deaths per annum, approximately).
A large part of this reduction in the incidence of typhoid and the now too often
forgotten conquest of the once-dreaded cholera is due to the improvement in water
supplies.
Prior to 1904 the water supply within the area of the London County Council
was in the hands of eight water companies, the oldest of them dating from 1619.
The first effective method of water purification by sand filtration (as opposed to the
old ineffective method of settling in reservoirs) was applied by one company (Chelsea
Company) in 1829. This lead was followed by all except three companies until 1852,
when the Metropolis Water Act was passed making such filtration compulsory and
also making it obligatory to cover all reservoirs within five miles of St. Paul's
Cathedral (the approximate City centre).
The studies of Dr. John Snow during the eighteen-fifties which demonstrated
that cholera was spread by water and that its incidence varied directly with the
degree of faecal contamination of the water, had a powerful effect upon informed
opinion, and contributed to subsequent legislation. (See " Snow on Cholera
a reprint of two papers by Dr. John Snow, M.D.—New York. Commonwealth Fund,
1936.) By 1856 all companies had moved their intakes from the influence of the tide
(another provision of the Act) and were delivering filtered water.
From 1856 onwards the story is of gradual but steadily progressive improvement.
In 1871 the Board of Trade were given powers for water examination in London.
These powers were transferred to the Local Government Board (predecessors of the
Ministry of Health) in 1872. Routine bacteriological examination of the Metropolitan
supply commenced in 1885. In 1904 the Metropolitan Water Board (a public
authority) took over the supply of water from the private companies. The work of
Sir Alexander Houston demonstrated that pre-filtration storage assisted the reduction
in disease producing organisms. In 1923 more rapid filters were introduced to remove
particulate matter before secondary filtration, but this increase in speed made it
necessary to introduce chlorination. Chlorination was first employed in a well-supply
in 1910, for river water before filtration in 1916, and for river-derived filtered water
in 1921. In the last case taste difficulties were encountered, but these were overcome
by the introduction of chloramine treatment at Kempton Park in 1929, and by 1936
all water passing into supply was treated by the ammonia-chlorine process. In 1921
water examination powers of the Ministry of Health were abolished and replaced by
those of a Water Examination Department of the Water Board.
To sum up, real progress began with the introduction of the slow sand filter and
the removal of the intakes to points above Teddington Weir, and has proceeded
steadily until, in 1948, 99.8 per cent. of all samples representing the water pumped
into supply complied with the highest standard of bacterial purity.
What was the parallel effect upon the incidence of disease ? In the early part
of the 19th century outbreaks of cholera occurred in London at intervals of a few