16. Routine sampling of nightsoil was carried out throughout the year as part of Hong Kong's anti-cholera surveillance programme. This measure now provides very useful epidemiological information about the presence or absence of infection in Hong Kong, the locality likely to be infected and the possible extent of infection. Apart from nightsoil sampling other public health preventive measures include routine bac- teriological investigation of specimens sent to the Government labora- tories of cases of gastro-enteritis as well as sampling of well water and foodstuff liable to be involved in the transmission of the vibrio. No positive samples were obtained from these investigations. The routine investigation on the frequency of isolation of non-agglutinable vibrios was continued during the year. As with previous years a mass immuai- zation campaign against cholera was started in April and by the end of the year a total of 1,318,991 inoculations were given.
Amoebiasis
17. The disease continued to remain endemic, particularly in the overcrowded areas. A total of 154 cases were notified and the disease remained predominant among adult males.
Bacillary Dysentery
18. A slight increase in the number of notifications was recorded. The disease occurs at all ages, but 44.8% of the notifications were in children under the age of 5 years. Shigella flexneri and Shigella sonnei remained the predominant organisms isolated.
19. Transmission of infection among families and in institutions is a feature of the disease and very often a number of symptomless carriers are detected from members of the same family or from inmates of the same institution. In all a total of 392 carriers were discovered during investigations of reported cases. They were all given appropriate
treatment.
Chickenpox
20. This is a very common disease amongst children. 97.2% of the cases reported were under 15 years. As with measles the seasonal prevalence of the disease is in winter and spring and hence the carlier part of the year saw an increase in the number of notifications.
Diphtheria
21. As a result of annual immunization campaign which has been in progress since 1959, the incidence of the disease has shown a con- tinuous and steady decline falling from 73.0 per 100,000 population in 1959 to 5.8 in 1967. The disease affects largely children and 77.8% of the cases were under the age of 10 years. The case fatality ratio în 1967 was 7.9% and death occurred primarily among the unimmunized children. Corynebacterium diphtheriae muitis remained the predominant organism isolated in clinical cases.
22. A total of 46 carriers were discovered amongst contacts of reported cases; each was treated and, if necessary, isolated until proved free of infection.
Enteric Fever
23. Typhoid fever showed a slight increase in incidence in August and September. The disease in Hong Kong is generally mild and the case fatality ratio is less than 2%. Transmission of infection is frequently associated with neglect in personal and food hygiene. As elsewhere the peak incidence occurred in children of school age and young adoles- cents. Free inoculation is offered and the usual preventive measures are enforced with special attention to environmental and food hygiene and the control of food premises.
Malaria
24. The incidence of malaria showed a notable reduction during the year, the disease being restricted mainly to certain parts of the rural areas in the New Territories. The majority of the cases were reported from the shores of Tolo Harbour and from the outlying islands at the mouth of the Tolo Channel. Of the three fresh cases reported from the urban area of Kowloon, one was due to blood transfusion while in the other two the infection was probably contracted in the New Territories where the affected persons had recently stayed. Plasmodium vivax remained the predominant parasite responsible for infection.
Measles
25. As shown in Figure 4, measles in Hong Kong has shown a distinct biennial pattern with exacerbation of the disease every alternate winter and spring. The last epidemic occurred in the winter months of
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