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21
1943-44 but the 1936-37 level was not attained in London. The highest weekly
mortality rates per million reached during the year were :—
London
Manchester
41.6
102.2
Birmingham
Great Towns
67.3
60.0
In the diagram the 1950-51 weekly deaths for London are shown in greater
detail. The continuous line at the top relates to deaths over 55 years of age;
the lower continuous line with the circled points relates to deaths under 55. The
broken lines denote the averages for the corresponding weeks in non-epidemic years
1945-48. Temperature, rainfall and fog are also shown.
It will be seen that most of the deaths occurred at very advanced ages.

Deaths under 55 attained a peak in spite of higher temperature and absence of
fog. Deaths over 55 peaked at minimum temperature and maximum fog. The
effect of low temperature and fog in increasing the death rate from non-specific
chronic respiratory disease has been previously noted, and it appears that many of
the deaths in this epidemic at ages over 55 were in those already suffering from
chronic respiratory infection. It is to be noted that the rise in deaths over 55 attained
a maximum somewhat later than the younger age groups; also that the incidence
of influenza in younger persons as measured by the deaths rose to five times and in
older persons to ten times the average non-epidemic level of 1945-48.
Measles
Measles became notifiable in London in 1938. Before that year records of
incidence were built up from reports of school absences, hospital admissions and
death records. Until the outbreak of the war of 1939-45 there had been biennial
epidemics of such magnitude that more than 70 per cent. of children suffered an
attack before age 15. The evacuation movements of 1939 and subsequent war years
disturbed this rhythm and since 1940 the outbreaks have been annual and of about
the same order of magnitude each year.
In 1950 there was a delayed sub-normal outbreak of measles which did not
reach peak until mid-summer. This was followed by a marked rise in cases again in
the autumn heralding a major epidemic which finally reached a peak of 3,754 cases
in the eighth week of 1951 with a sub-peak in the first week of that year (2,730
cases). The total cases notified during the year 1951 were 49,148. After the peak
was attained there was a steady fall in weekly cases and the epidemic gradually
petered out—in the twenty-sixth week the cases numbered only 229 and during the
last week of the year only 19 cases were notified. Ignoring the small outbreak in
1950, which can now be seen to be the beginning of the 1951 epidemic later
temporarily interrupted by the autumn refractory period, the interval between the
peak of the 1949 outbreak and that of 1951 was 96 weeks so it would seem that
owing to the decrease in susceptibles with the fall in the birth rate since 1947 the
rhythm of measles epidemics is now moving towards a biennial period as existed in
the pre-war period 1923-38. The attack rate of 14.64 per thousand in 1951 was
the highest incidence known since notification became compulsory in 1938.