View report page

128
Annual Report of the London County Council, 1911.
rates being half those of Great Britain. National characteristics evidently make a great factor in
this prevalence. These diseases vary secularly with time. Fig. 7 shows the death rates from the
three chief school zymotics year by year for the past 25 years in London. It will be seen that these
diseases show a diminished prevalence in recent years, although in measles this is least marked. As
regards diphtheria especially, this may be due to the unknown causes hidden under the term "epidemic
constitution," but probably is mainly due to increased spread of knowledge and care for the sick. The
dotted part of the measles line gave an estimate in November of the 1911 measles death rate which
actually was 570 as shown in the figure.
There is very imperfect knowledge of the number of measles cases occurring, the ages of incidence,
and the fatality rate. One attack gives great protection against future attacks. Of 24,256
cases compulsorily notified in Aberdeen in 1893-1902, only 2.46 per cent, were supposed to be second,
and 0.05 per cent, third attacks. In attempting to set forth the incidence of cases at different ages,
the relative protection of previous attacks has almost always been neglected. Many writers have
fallen into errors and concluded that there is a lessened liability to attack at higher ages, a conclusion
which is not justified by the experience of isolated communities, and only possible by neglecting the
immunity already existing in the population.
In London information as to the number of cases existing is frequently derived for public health
purposes from second or third-hand reports furnished by school teachers, attendance officers, and others
to the education and sanitary authorities. Another source of information is in the mortality returns.
Unless a school child lives in a family where a case of measles develops, or a death from the disease
occurs, there is little probability of the occurrence of cases of measles being known. Careful studies,
inaguratcd by our Woolwich Enquiry of 1902-1906, have shown that at different seasons from one-third
to three-quarters of the children entering school have suffered from the complaint. This proportion
will vary from year to year and to very great extent. The following table shows the percentage case
mortality (Aberdeen, 1893-1902) in Aberdeen, where notification was compulsory,

These mortality case rates for measles are taken over a large number of cases spread through
several years, and whilst they are probably fair averages (3.3 per cent.) will err in excess rather than
deficit, owing to the mild cases which are non-fatal and escape notification. The total mortality (3.3
per cent.) is justly comparable with the average of 3.5 per cent, found in Edinburgh, where notification
existed from 1880 to 1901, and where there were 2,882 deaths among 82,544 cases known by
notification. Taking the mortality returns given by the Registrar-General for London for 1909, an
estimate,

It must be remembered that these figures are merely an estimate which shows the probable
ratios, but which as actual numbers may be liable to an error of 5 per cent, or 10 per cent. There
is reason, however, to suppose that they understate the case for London at school ages.
This gives 77,000 to 78,000 as a low estimate for the probable number of cases in London during
1909, but only 20,100 cases were notified through the schools. In 1910 there were 1,980 deaths, and
25,677 cases notified. The crude death rate was 440 per million living. In 1911 there were 2,570 deaths
and 31,905 cases notified, corresponding to a crude death rate of 571 per million, a trifle below the mean
annual rate for the sixty years 1841-1900. The number of cases coming to notice through notifications
does not seem to be more than about one-third, even when followed almost hourly as in the recent
outbreak. These facts are only partly explained by second or third cases in a family failing to be notified.
This estimate is borne out by a very careful study of measles at St. Helen's by Dr. Paterson.
He found that of 1,367 cases known through notification, 41 cases died, exactly 3.3 per cent, as in the
Aberdeen returns. There were actually 170 cases of deaths from measles registered, which, at the
Aberdeen case rates, would indicate the probable cases at 4,038. From this he deduced that only
33.8 per cent, of cases came to light by the school returns in St. Helen's.
Figure 9 has been constructed on the basis of the returns at Aberdeen, Edinburgh and St.
Helen's, to show the distribution of cases probably occurring during 1909, and the amount of actual
knowledge of them obtained from the school returns in London.
Mortality is discussed rather than case incidence, because for practical purposes this last, if a
thorough knowledge of the cases could be got, would vary with the birth rate and the child population