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90. Though paddy swamps on the open plains are factors of little importance in the spread of malaria, the same cannot be said of the irrigated terraces which form the rice fields of the hilly country. These have been shown by the Malaria Bureau to be, under certain conditions, prolific breeding places for that powerful carrier A. jeyporiensis. The irrigation ditches leading to and from the rice fields harbour both A. jeyporiensis and A. minimus.
91. Here, as in Malaya, disturbances of the soil often result in the formation of small collections of water which, for reasons unknown, attract the malaria mosquito and in which they deposit their eggs. The breaking of the soil is not a direct cause of malaria but a predisposing factor in a chain of events which favour the spread of the disease.
92. The most malarious areas are, therefore, those in or near the hills. Unless carefully watched and carefully controlled, works in the vicinity of the hills which involve disturbance of the soil, such as roads, railways, or waterworks, are nearly always attended by high sickness and death rates among the labour forces employed. In Malaya, this was especially the case when the soil was of granite formation, and the same applies in Hong Kong.
93. Malaria not being a notifiable disease, few figures are available to measure the actual extent of incidence throughout the Colony and New Territories.
94. On the hospital returns and on the returns furnished by certain government departments, such as the Police, it is possible to base a guess as to whether the disease is on the increase or decrease generally, but that is all.
95. The cases admitted to Government Hospitals numbered 475, of which 8 or 1.68 per cent died. In the Chinese Hospitals, there were 925 admissions, of which 208 or 21.40 per cent died.
Among those admitted to the Government Hospitals, there were 195 tertian, 159 aestivo-autumnal, and 12 quartan infections.
96. The cases admitted to the Government Hospitals during the last nine years are as follows:
1925 1,142 1926 970 1927 670 1928 485 1929 653 1930 535 1931 585 1932 465 1933 475