as well as sampling of seawater, well water and foodstuffs liable to be involved in the transmission of the vibrio. All such samples were negative. Routine investigation on the frequency of isolation of non- agglutinable vibrios was continued, but there was no notable variation in the pattern of non-agglutinable vibrios isolated at the time the case occurred. A mass immunization campaign against cholera started in April and was repeated in November. By the end of the year a total of 1,467,271 inoculations had been given.
17. There was no apparent link between the cholera case at Kowloon and the positive nightsoil findings at Hong Kong Island. No further case was reported and the Colony was declared free from infection on 5th December.
Amoebiasis
18. 220 cases were notified in 1966 compared with 173 in 1965. The disease continued to occur sporadically and the extent of community infection is, as elsewhere, not definitely ascertainable.
Bacillary Dysentery
19. The number of notifications increased from 537 in 1965 to 766 in 1966, giving an incidence, as measured by notification, of 20.7 per 100,000 population; 43.8% of the cases occurred in the age group of under 5 years. As in previous years, Shigella flexneri and Shigella sonnei remained the predominant organisms isolated.
20. During investigations of the reported cases, a total of 231 symptomless carriers was discovered and appropriate treatment ad- ministered.
Chickenpox
21. A reduction in the number of notifications of this disease was recorded in 1966, and 72% of the cases occurred in children below the age of 5 years. During the first 3 months of 1967 there was an increase in the incidence of the disease.
Diphtheria
22. As demonstrated in Figure 3, diphtheria incidence has shown a continuous decline since the commencement of an intensive and year- round immunization campaign in 1959. The incidence of the disease was 8.3 per 100,000 population in 1966 as compared with 73.0 per 100,000 in 1959. Although somewhat disrupted by the cholera and poliomyelitis
immunization campaigns of recent years, this programme continues to give encouraging results. Corynebacterium diphtheriae mitis remained the predominant organism; consequently most cases presented with laryngeal symptoms. Approximately 79% of cases occurred in children under the age of ten. The case fatality ratio in 1966 was 8.8 per cent. partly due to the fact that a number of cases do not seek immediate medical treatment, and patients admitted into Government hospitals often give a history of having been treated by herbalists in the first instance.
23. A total of 39 carriers was discovered amongst contacts of reported cases; cach was treated and, if necessary, isolated until proved free of infection.
Enteric Fever
24. Typhoid fever incidence remained at about the same level com- pared with last year. This disease in Hong Kong is generally associated with neglect in personal and community hygiene and its decrease in recent years is probably connected with improvements in water supply. As elsewhere the peak incidence occurred in children of school age and young adolescents. Free inoculation is offered and the usual control measures are enforced with special attention to the detection of carriers among food handlers.
Malaria
25. The incidence of malaria continued to decline, the disease being restricted mainly to certain parts of the uncontrolled rural areas in the New Territories. The majority of the cases reported during the year were from the Tai Po District situated on the shores of Tolo Harbour. The reduction in incidence in Sai Kung District in recent years is probably due to development taking place in the area with resulting reduction in cultivated land thus reducing the breeding places of malaria vectors. The malaria incidence on outlying islands at the mouth of Tolo Channel often fluctuates which might be due to the introduction of new sources of infection through fishing junks. Of the six fresh cases appear- ing in the controlled urban areas, one was an imported case while in the other five the infection was most probably contracted in the New Territories where the affected persons had been recently employed. Plasmodium vivax remained the predominant parasite responsible for the infection.
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