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41
As already stated, and as will be seen by reference to diagram XVI., the year 1899 was characterised
by excessive prevalence of enteric fever in the latter part of the year. There was marked increase
above tho average in the 40th-46th weeks, the increase being most manifested in the 43rd, 44th and
45th weeks. Thus there was a marked increase in the number of cases notified in the 40th week
(week ending 7th October), a fall in the 41st week, and from that time a rapid rise in each successive
week, 42nd, 43rd, and 44th. The prevalence showed a trifling decline in the 45th week and a rapid
decline in the 46th week, after which the fall in each successive week (with one exception) was continuous
and rapid. This excess of prevalence was manifested over wide areas of London, both on the
north and south of the Thames, the districts on the north of the river which were most affected being
those in the east of London.
It is interesting to observe that some difference in the relative proportion of males and females
attacked is observable in the year 1899 when compared with the two preceding years. Thus, in 1899,
in the four weeks 42-45 the proportion of females attacked was greater than in the rest of the year,
in 1897 and 1898 it was less in these four weeks than in the rest of the year. The actual proportions
were as follows—
No. of females attacked, per cent, of total attacks.
Year. No. weeks, 42.45.In rest of year.
1897 43.3 45.3
1898 40.3 44.0
1899 48.1 44.2
It will be seen, therefore, that in 1897 and 1898 the proportion of females was less in the
weeks in question than in the remaining portion of the year, and that in 1899 the position was reversed.
When the proportion of females over fifteen years of age in the four weeks in question in 1899 is compared
with the proportion in the corresponding period of the two preceding years, it is found to be somewhat
smaller. Thus the number of females over 15 years of age per cent, of total females attacked was in 1897
693 per cent., in 1898 67.1 per cent., and in 1899 65*1 per cent. Again when the lists of notified
cases of infectious disease are examined it is found that secondary cases in invaded houses were
greater in 1899 than in the preceding two years. Thus the proportion of secondary to total cases in the
latter six months of each of these years was—1897, 8-7 percent.; 1898, 8-9 per cent.; 1899, 10'9 per
cent. In connection with possible causes of the behaviour of enteric fever in 1899 it is deserving of
notice that floods in the rivers did not precede the increase under consideration as in 1894, when
they preceded an increase which I believe was due to pollution of water supply. There was, however, in
the large excess of cases in the 43rd, 44th, and 45th weeks, suggestion that some undiscovered
infected food supply was contributing to the total prevalence which occurred during these weeks. As
the result of considerable enquiry in those districts in which the prevalence of the disease was most
marked, I have been unable to obtain any evidence indicative of a particular common cause of enteric
fever in the weeks mentioned. Apart from the increase in these weeks, there was, as will be seen on
reference to diagram XX. (page 50), larger autumnal prevalence of this disease than in any recent
year, and it may be stated that during the last few years there has been increasing autumnal prevalence,
probably due to natural causes. The behaviour of enteric fever in this respect may be compared
with that of scarlet fever and diphtheria by reference to diagrams XVIII. and XIX. (page 50).
Enteric fever—Age and sex distribution.
In the year 1899 the case rate, death rate, and case mortality, were greater among males than
females. The case rate of males was greater than that of females at each age period except 55 years
and upwards ; the death rate of males at ages 5- and 10- was less than that of females, but at each
subsequent age was greater except at 55 years and upwards. The case mortality of females at ages
0- 5- 10- and 15- was greater than that of males, but at each subsequent age period, except 45and
55 and upwards, was less than that of males. This will be seen from the following table—

* fee footnote (*), page 34.
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