M 55
It will be noticed that the total cases of these diseases is the highest recorded for the last ten years, namely 302 cases; the next highest figure being 249 in the year 1918.
The estimated population (excluding that of the New Territories) for 1918 was 468,100, while for 1923 it was 597,300.
The factor of increase of population for 1923 on that of 1918 is thus 1.27. The factor of increase of the Typhoid and Paratyphoid cases for the same year is less, namely 1.21.
There are many ways in which infection of these diseases may be acquired. In the first place, it is noteworthy that the water-flush system of disposal of night soil is adopted in few buildings in the Colony. There are thousands of privies and commodes in the Colony in which night soil is exposed and which may be visited by flies. Fortunately, flies are not in this Colony so plentiful as in some Eastern cities, but they may undoubtedly be a factor in the contamination of food by typhoid bacilli.
The Chinese method of manuring vegetables with human excreta is also a possible source of infection.
To what extent carriers of typhoid exist here is unknown.
An attempt was made several years ago to estimate the number of probable carriers by the examination of a few hundred Chinese employed in the preparation and handling of food, but by the time somewhat less than one hundred preliminary blood tests had been made, the passive resistance of these employees caused the experiment to be abandoned.
Some few decades ago, there prevailed in this Colony an opinion that Chinese, at any rate those of this Colony and the near Province of China, were generally immune to Typhoid.
It is probable, therefore, that many cases of this disease and of Paratyphoid were not diagnosed as such.
With the introduction of more careful pathological and bacteriological methods, this opinion has been greatly modified.
The great increase of Chinese medical men trained in Western medicine has also probably been a factor in bringing to light the existence of much more Typhoid amongst the Chinese than was formerly supposed.
Immunity is not absolute but relative, and it may be that the Chinese do have generally a somewhat higher degree of immunity to Typhoid than do Europeans.