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63
Report of the Medical Officer of Health.
as that made use of in the years 1910 and 1911 there is clear evidence that there was in the two later
years a marked diminution in the proportion of infested beds. The lessened prevalence of vermin
though affected in noteworthy degree by climatic changes, heat and cold, sunshine and rain, is without
doubt in large measure due to the increased amount of attention devoted to infested clothing and
bedding, and to the improved facilities for personal cleansing provided in the more recent years.
In the report for 1909 reference was made to the fact that the high autumnal level in the flea
and bug curves suggested comparison with the curves of diseases which have an autumnal prevalence.
Having regard to the attention which has been devoted to study of the curves of seasonal prevalence
of flies and diarrhoea, it becomes a matter of interest to examine a little more closely the rough
correspondences observed, in the case of the curves for fleas and certain diseases prevailing in the
autumn, with a view to learning whether they throw any light upon the general question of the possibility
of infection by insect carriers. The report just referred to continues :—
"In the cases of scarlet fever and diphtheria, there are certain facts which suggest the desirability
of keeping an open mind as to whether the last word has been said concerning the mode of
spread of infection. For example—the special incidence upon children, and particularly upon children
in schools; and the evidence as to fomites and the alleged clinging of infection to houses or rooms, or
in schools to particular departments or even classrooms.—Dr. Niven has referred (Annual Reports,
1897-1901) to evidence of 'the tenacity of the disease as regards particular departments.' He says,
'It may go on for a year or more in a department, attacking a case in May, another in June, another
in July, and so on.' Again, he observes, 'The history of scarlet fever in schools seems to imply a low
power of aerial transmission.'
"Furthermore, mention may be made of the fact that scarlet fever rarely spreads from an infected
to an uninfected child in the ward of a well-managed hospital, but such spread does occur ('return
cases') after children are sent back to their homes. Mr. T. W. Thompson (Vol. XV. Epidem. Soc.
Trans.), in discussing the 'return case' problem, enumerated possible causes of the differing incidence,
on one as compared with another class of household. He referred to the influence of school attendance
social circumstances, etc., but concluded, 'some more obscure factors are at work, factors perhaps closely
bound up with the natural history of scarlet lever; The possibility cannot, of course, be absolutely
excluded that a biting insect has played a part in transmitting infection from case to case in some
instances, and that in the absence of such intermediary infection has not been transmitted.''
In the year 1909 the London scarlet fever and diphtheria curves, it may be said at once,
were quite atypical. A considerable milk outbreak of scarlet fever occurred in June and July, and
disturbed the ordinary development of the rise usually observed in those months. Apparently, however,
the true autumnal maximum for scarlet fever occurred in the thirty-eighth, and that for diphtheria
in the thirty-ninth week, while the maximafor both the biting insect curves occurred in the thirtyfifth
week. There was thus an interval of three or four weeks between the attainment of the maxima
in the latter instances and in the former.'' (N.B.—The dates of ending the several weeks given in
diagram Y are those for 1911.)
In 1910 the maximum for scarlet fever occurred in the thirty-ninth week, and for diphtheria in
the forty-first week (see diagram Y), whilst the maximum for fleas occulted in the thirty-sixth week, thus
giving an interval of from four to five weeks. In 1911 the maximum for scarlet fever occurred
in the weeks ending October 14th and 21st, and that for diphtheria not until November 18th. The
maximum for fleas in this year was reached in the week ending August 19th, the interval of time
between the respective maxima being from 8 to 13 weeks, and thus was greater than in the two former
years.
In the Report of 1909 already referred to comment was made upon the interval between the
attainment of maxima in that year and it was stated that—
"In the case of flies and diarrhoea, no such interval is, as a rule, observed, the curves are practically
superimposed one upon another. The bearing of this fact upon the hypothesis of fly causation
of diarrhoea has been already considered, and it has been pointsd out that there is, in the absence of any
such interval, little, if any, time available for dissemination of infection, incubation, etc. It must
be remembered, however, in this connection, that there is no need for time for development of an
organism in the body of the fly. The suggestion has never been made that the hypothetical organism
of diarrhoea passes a phase of its existence within the fly in the manner demonstrated for the malaria
organism within the mosquito. If the fly merely acts as a carrier there is, at any rate, no question
of allowing time for such development."
"It will be interesting to learn whether or no the figures for future years confirm those of last
year, in respect of showing an interval between the time of occurrence of the maxima for fleas (or bugs)
and the maxima for scarlet fever and diphtheria. Obviously, at the present time, no more can be
said than that the subject is one deserving of further study."
It will be observed that the figures for 1910 and 1911 exhibit an interval between the time of
occurrence of the maxima for fleas and the maxima for scarlet fever and diphtheria. The interval in
1910 is, however, one week longer, and in 1911 five weeks longer than in 1909.
Water supply to tenement houses.
Sanitary authorities have increasingly used the powers provided by section 78 of the London
County Council (General Powers) Act, 1907, for requiring the provision of a water supply to the upper
floors of tenement houses.