PUBLIC HEALTH
129
disease which tends to be somewhat reglected by parents, is all too often followed by serious complications and death.
Scarlet fever. Following the unusual outbreak in May 1955, this disease again appears to have virtually disappeared from the Colony.
Malaria. 'Protected' areas, in which control methods are applied, now comprise the whole of the Island, the urban areas of Kowloon and certain selected parts of the remainder of the Colony. In order to avoid as far as possible the danger of developing resistance amongst anopheline mosquitoes to insecticides by combining the use of chlorinated hydrocarbon insecticides simultaneously as larvicides and as adulticides, it has been considered advisable to discontinue D.D.T. residual spraying in the villages on the perimeter of the larval controlled areas as from the beginning of 1957.
80 per cent of all cases notified originate from unprotected areas. The apparent increase in the incidence follows a tight- ening up on notification after it had come to light that a large number of cases occurring in certain rural areas, where there is a tendency to regard the disease as 'normal', were not being reported. Malaria surveys of young children have been conducted in the unprotected areas, and the result in- dicated considerable variation between different localities. Spleen rates and parasite rates, however, were found to be gratifyingly low, and the disease does not present a major problem in this Colony.
The cost of the present malaria control measures is approxi- mately 34 cents per head of population per annum, and this small expenditure includes also the control of nuisance mos- quitoes in certain areas.
Poliomyelitis. During the year 31 cases of poliomyelitis occurred sporadically in various parts of the Colony. The incidence was highest in the third quarter of the year (21 cases), infants and young children being mainly affected. The risk of infection appears to be distinctly greater among