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22
An important feature is the reduction in the case mortality in measles. The
figures are:—
Years Estimated cases* Deaths Crude case mortality per cent.
1921-25 271,500 3,868 1.43
1926-30 321,000 3,885 1.21
1931-35 208,000 1,912 0.92
1936-40 170,750 876 0.51
1941-45 84,925 170 0.20
1946 22,846 21 0.09
1947 17,486 23 0.13
1948 30,608 26 0.085
1949 28,816 16 0.056
1950 22,282 4 0.018
1951 49,148 25 0.051
*Actual notifications since 1939.
Most measles deaths are due to respiratory complications and the more recent
reduction in mortality can largely be attributed to the use of the sulphonamides and
anti-biotics in the prophylaxis and treatment of the respiratory complications. A
steady decrease in mortality was however in progress long before the more recent
accelerated fall.
Ophthalmia
neonatorum
The incidence of ophthalmia neonatorum which since 1921 has remained fairly
constant between 8 and 10 new cases per thousand live births commenced to fall
slightly towards the end of the period 1931-40 and in recent years has fallen to below
5 per thousand live births. There were 93 cases in 1951 (1.8 per thousand live
births) full details of which are shown below.

Pneumonia
Notified cases of pneumonia in 1951 numbered 2,409 or 0.717 per thousand,
compared with 0.499 per thousand in 1950. This disease is considerably undernotified
particularly at ages over 65 and it is believed that over the whole age-range
only about one-quarter to one-third of the total cases are notified. There is, however,
no reason to believe that this fraction varies from year to year so that the notifications
may still be used as a relative index of incidence. It will be seen from Table 9 that
the 1951 notification rate is lower than either war-time or pre-war rates. See page
12 for comment on the death-rate.
Poliomyelitis
and polioencephalitis
During the year 112 cases of poliomyelitis occurred according to corrected
notifications and there were 2 deaths giving a crude case mortality of 1.8 per cent.
In the 1950 outbreak there were 430 cases and 36 deaths so that the 1951 incidence
was much lower than that of the previous year. In 1951 24.1 per cent. of the cases
were infants under 5 years of age compared with 34.9 per cent. in 1950.
The variations in age distribution are interesting. Before 1947 the percentage
of cases under 5 had been falling since 1930 and the proportion of adult cases had
been rising as will be seen in the following table. The rise and subsequent fall in
this percentage from 1947 onwards will be noted.