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Scarlet Fever lias shown a succession of shallow waves o
incidence with a distinct trend towards an aggregate increase. The
periods of maximum intensity have been in 1924, June and July;
1925, March, April and May; 1926, May, June and July; 1927.
April, May and June; 1928, January and February, with another
in November and December. 1929, a gradual increase throughout
the year without any intermissions. During 1930 the incidence has
been relatively constant, with a slight decline in the number oi
cases in August and September. The weekly average of cases has
been 15.
Diphtheria.—During 1924 there was a small but steady incidence
throughout the year; in 1925 a trough occurred in the curve
and very few cases were notified, but towards the end of the year
the notifications began to increase steadily, the curve reaching its
apex in November and December, 1926 ; the curve then declined
through 1927 until the last quarter, when the trend became upwards
once more, reaching its apex in January, 1928, this was followed
by a slight fall, followed by a slight rise until December, 1928,
when another fall commenced, reaching its minimum in July, 1929,
from when the curve rose steadily to its maximum in November.
In 1930 Diphtheria was not troublesome, though there was a small
rise in the number of cases in October, reaching a maximum of 22
during the week ending October 18th. The weekly average was 7.
Whooping Cough, from being inconspicuous in 1924. the
curve rose gradually to a maximum in May, June and July, 1925.
then fell rapidly to a minimum in November and December, then
rose very gradually to a lower maximum in September, 1926; once
again the curve fell abruptly to a minimum in January, 1927, rose
in June and July, and fell again gradually to a minimum in November
and December, then rose steadily to the highest level of the
period under review in January, 1929, from when it fell steadily
to the end of the year. Throughout 1930 it remained quite inconspicuous,
until December when there were indications of the commencement
of a wave of increased incidence. Until December the
average number of cases brought to our knowledge was two weekly.
Measles was very prevalent in April and May, 1924, thee
dropped suddenly, but showed a small rebound during September.
October and November, after when it died away until a sudden rise
in May, June and July, 1925, was followed, after a fall, by a
further and more prolonged rise from October, 1925, to May, 1926During
1927 there was very little Measles in Croydon; a small rise