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low attendance after the first week in December probably does not represent relatively many new cases
of illness. The deaths from influenza were still high at the end of the year, but practically speaking
the epidemic came to an end in London about the middle of December.
The third epidemic commenced in the latter part of January last; the influenza cases removed from
the streets in the week ended 25th January being 6 as against 1 in the week preceding. The maximum
number of removals was recorded in the week ended 22nd February, being then 32, and by the
end of March the epidemic had practically subsided. Including pneumonia the total cases removed from
the streets by the Council's ambulance in the three epidemics numbered 18, 451 and 174 respectively.
Children of school age were far less affected during the third prevalence than in the two earlier
outbreaks. While this epidemic declined more rapidly than that of the autumn, there was a slight
recrudescence in April, and for several weeks the influenza death-rate remained somewhat in excess of
that in the weeks immediately preceding the epidemic.
The severity of the epidemics may be regarded from two points of view, firstly as to the relative
number of cases and secondly as to the relative number of deaths. In regard to cases it may be observed
that in the week ended 13th July, at the height of the summer epidemic, the percentage attendance in
the Council's schools had fallen to 73.4 In the autumn in the week ended 2nd November, the attendance
fell to 70.2, this being the lowest attendance rate recorded in the autumn session. The longer duration
of the autumn incidence is well shown in the effect upon school attendance, the amount of school time
lost being about twice that lost in the summer. Among adult workers, the sickness rates
indicate a loss of working hours between two and three times greater in the autumn than in the summer.
The relative number of cases stands, however, in no relation to the severity of the type of influenza in.
the two epidemics, since in the summer the deaths in seven weeks among children aged 5-15 numbered
75, an average of about 11 per week, while in eleven weeks of the autumn epidemic there were 1,057
deaths, an average of 96 weekly. The contrast is not quite so great when deaths at all ages are compared.
It, therefore, appears from the attendance rates among school children and sickness rates among
adults, considered in relation to deaths in the two classes, that while clinical cases of influenza in the
autumn were about twice as numerous as in the summer, the deaths, registered from or attributable to
epidemic influenza were more than ten times, and the case mortality was about five times as heavy.
Figures available in respect of towns where either complete or partial notification was in force,
indicate that the deaths in the autumn were disproportionately in excess of the cases when compared
with the figures for the summer epidemic. Thus in Copenhagen the cases notified during the autumn
epidemic were about two and a half times the number in the summer, but the deaths were probably
eight times as numerous. In Stockholm, where returns are made of cases treated among the poorer
classes, the autumn cases were three times and the deaths about eight times those of the summer. In
Gothenburg the ratios were similar to those for Stockholm. In Christiania, however, while the cases in
the municipal hospital were as three to one. the deaths were only as four to one. The death-rate from
all causes in Christiania during the summer epidemic rose proportionately more than in any of the
principal capital towns for which figures are available.
The relative
severity of
the
epidemics.
The deaths in London certified to be due to influenza from the middle of June, 1918, to the 3rd May,
1919, numbered 16,520 and of these about 989 may be allocated to the Summer, 11,898 to the Autumn
and 3.633 to the Winter erridemic.
Estimate of
deaths
caused by
the three
epidemics.
The total deaths caused by the epidemics may be approximately ascertained from a comparison (
of the weekly deaths in 1917' and 1918 in the periods of epidemic prevalence. Taking the period 23rd
June to 10th August as broadly representing the limits of the summer prevalence, it will be found that
in the two weeks preceding and following this period there were about 109 deaths per week less in 1918
than in 1917. Assuming that the deaths between 23rd June and 10th August, 1918, would, in the
absence of influenza, also have averaged 109 per week less than in 1917, the total in this period would
have been 5,370. The actual deaths were 7,553. Hence 7,553 — 5,370 = 2,183 deaths would, as thus
estimated, appear to have resulted from the epidemic. Of these about 40 per cent, were among males.
The method used in estimating the total mortality due to the summer epidemic is justified by the
generally stable mortality in the summer months. In the autumn, however, the rates fluctuate widely
under the influence of changing weather conditions, and it happens that in December, 1917, exceptionally
unfavourable conditions caused high mortality. In the autumn epidemic, therefore, comparison is
limited to the 13 weeks ended 14th December, and in this period the actual excess in deaths in 1918
over 1917 amounted to 15,767 (6,755 males and 8,992 females), and this number is taken to represent
the effect of the epidemic.
The resulting estimated total deaths for the two epidemics would, therefore, amount to 7,756
males and 10,174 females, a total of 17,930 persons. The estimated mortality from the summer
epidemic given is probably rather too high ; on the other hand, deaths resulting from the autumn epidemic
occurred for some weeks after the date, 14th December, taken as marking its close, and the resulting
estimate is likely to be understated. In round figures about 18,000 deaths in all resulted from the two
epidemics, 43 per cent, of which were deaths of males.
In the third outbreak during the first quarter of this year some 5,000 deaths may probably be
referred to epidemic influenza; but in view of the wintry weather which prevailed during the early weeks
of the epidemic it is difficult to arrive at a figure representing deaths attributable directly to the influenza
epidemic alone.
The increase during the course of the epidemic in deaths classified to other causes than influenza,
chiefly pneumonia, bronchitis, diseases of the heart and phthisis, is shown in the following table, which
enables comparison to bo made of tho three epidemics in this respect. The figures given, except those
for influenza deaths, are the estimated excess in deaths from the causes mentioned during the weeks
of marked epidemic prevalence.
Increase in
other causes
of death
during the
epidemics.