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Kong Island and all eleven routes in Kowloon were found, at one time or another, to be infected with cholera vibrios. This widespread dis- semination of the organism throughout the community is evidence of a large number of symptomless carriers, and was particularly noticeable in Kowloon immediately prior to the notification of the first case from the 'Temple Street Well'. The last infection of night-soil was reported on 28th June,
17.
Rouline sampling of foodstuffs, such as shell-fish, fresh-water fish and fruits, all proved negative. However, epidemiological investiga- tions of the homes of each patient were of some interest; seventeen of the homes, exactly 50%, showed wide dissemination of the vibrio. Places most commonly found infected were latrine pans, drainage out- lets, dustbins and food chopping-blocks.
18. Incidental observations, which are being further investigated, showed a variation in the frequency of isolation of non-agglutinable vibrios (vibrios not agglutinated by cholera anti-sera) suggesting waves of infection rather than sporadic appearance of saprophytic organisms. There was also remarkable réduction in such isolations following the appearance of cholera El Tor. The significance of these findings is not clear as yet and further work is proceeding.
Amoebiasis
19.
Amoebic dysentery and its sequelae continued to occur sporadi- cally and the extent of community infection is, as elsewhere, not definitely ascertainable.
Bacillary Dysentery
20. The incidence of this disease remained high during the drought conditions in the earlier part of the year, but showed a marked decrease to below-average incidence during the last seven months following the onset of heavy rains and subsequent relaxation of the severe water restrictions. As in previous years, the organisms commonly isolated were S. flexneri and 5. sonnei.
21. During investigations of the reported cases. a total of 139 symptomless carriers was discovered and appropriate treatment ad- ministered.
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. Although somewhat disrupted by the cholera and poliomyelitis immunization campaigns of recent years, this programme continues to give encouraging results. C. diph- theriae mitis remained the predominant organism: consequently most cases presented with laryngeal symptoms and, as in previous years, approximately 75% of cases were in children under the age of ten. The case mortality rate declined significantly from 9.87% in 1963 to 5.44% ia 1964.
23. During the latter months of 1964 single cases occurred in two schools and investigations revealed a total of twelve carriers, including one teacher, amongst the immediate contacts. In all. 114 carriers were discovered amongst contacts of reported cases; each was treated and. if necessary, isolated until proved free of infection.
Enteric Fever
24. During the first half of 1964, the incidence of typhoid fever followed generally the pattern of previous years; however, subsequent to
CASES NOTIFIED
166
2
AVERAGE I
FIGUNE 4
TYPHOID MA
JAN FEB MAR APK MAY MUN JUL AUG SEP OCT NOV DEC
7