ENG-1963 — Page 193

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HEALTH

cases. The important carriers of malaria are Anopheles minimus found breeding in certain hill streams, seepages and irrigation ditches, and A. Jeyporiensis var. candidiensis which breeds in rice cultivation, fallow rice fields, pools in rice stubble and water flow- ing through grass. Other anopheline species found in the Colony play little or no part in malaria transmission. Plasmodium vivax is the predominant parasite responsible for the infection.

Malaria control in the urban areas is based chiefly on anti-larval measures consisting of draining and clean-weeding streams, ditch- ing and oiling. Anti-malaria oil continued to be employed as the main larvicide, malathion, diazinon or BHC being also used on a limited scale in areas where the application of oil is not suitable. These anti-larval operations against anopheline breeding afford protection from the infection to over 80 per cent of the 2,500,000 or more persons estimated at mid-year to be living within the urban areas of Hong Kong, Kowloon and New Kowloon and in certain circumscribed zones in the New Territories. None of the few cases appearing in the urban areas during the year could be attributed to breakdown of these control measures. In the re- mainder of the New Territories, the background of which is essentially rural, the adoption of either anti-larval or anti-adult measures is not feasible at present. Therefore chemoprophylaxis remains the main protection against malaria for disciplined groups stationed there.

Diphtheria. Due to the rapidly increasing number of young children and the poor response to the facilities for immunization, there has been little significant decline in the incidence of diph- theria during recent years. The main foci are in the densely populated tenement areas of the Colony, overall incidence being evenly spread throughout all areas. Over 79.5 per cent of the cases were in children under the age of 10, with more than 58.5 per cent under the age of five. The case fatality rate from diphtheria has not shown a continuing decline during recent years, being 9.9 per cent during 1963 compared with 10.5 per cent in 1956.

As in recent years, the diphtheria immunization campaign was continued throughout 1963, with emphasis on inoculation facilities being made available as near as possible to the home. However, interruptions of the effort, due to the anti-poliomyelitis and the