HEALTH
147
eating places and food premises, markets and hawkers. Particular attention was paid to the collection and disposal of night-soil and to sampling of night-soil for pathological examination. The inocula- tion campaign continued and a total of 3,101,766 doses of vaccine had been given by the end of the year. Detailed epidemiological investigations of each case were conducted and the results remained consistently baffling. Cases occurred sporadically over widespread areas and no relationship could be determined between them nor could any common source or agent be found. No secondary cases from clinical cases or proved carriers occurred. In general, persons aged 43 and over were most affected, 47 per cent of all cases occurring in this group which comprises only 17.4 per cent of the total population. Of the 115 cases reported only 29 had been inoculated, and the disease was mild in the majority of this group.
Routine sampling from tanker vehicles containing communal night-soil was continued nightly throughout the year. These tankers serve approximately 25 per cent of the population of the urban areas, a percentage which is slowly but surely declining as water- borne sewage systems are extended. The first positive specimen was obtained on the night of 1st July, four days after the notifica- tion of the first case. By the end of the outbreak all of the 28 collection routes in Kowloon and 31 of the 34 routes on Hong Kong Island had yielded positive cultures of cholera vibrios, the Kowloon routes being positive for cholera vibrios on 370 occasions and the Hong Kong routes positive on 700 occasions. On certain occasions it was possible to trace the infection back through the hoppers serving the tankers to latrine buckets used in tenements; in some instances it was possible to obtain rectal swabs from the residents served by these buckets and a number were found to be positive although the persons concerned showed no other evidences of the infection.
The last case of the 1963 outbreak occurred on 21st December and the Colony was subsequently declared free of infection.
Tuberculosis. In spite of continuing satisfactory progress tuber- culosis remained the principal community health problem in the Colony. Many thousands of unselected examinations carried out each year show that just under two per cent of the adult population is in need of treatment for the disease, with a smaller percentage of active tuberculosis occurring below the age of 15.