rumours it was decided to take precautionary measures in Hong Kong and over the ensuing week-end the production of additional supplies of cholera vaccine was started, working on a shift basis. Cholera inocula- tion centres were designated, to open on Monday the 14th August, hospital and other staff most at risk were inoculated, and plans made to open cholera treatment centres and to intensify all necessary measures of environmental sanitation,
86. On Monday, the 14th August, a case of cholera was confirmed in Macau and Hong Kong imposed quarantine restrictions on Macau and the Kwangtung Province of China. Inoculation Centres were opened op on that day, the chlorination of unprotected well water supplies started in the urban areas, food inspections intensified, treatment centres prepared and a quarantine centre designated. Through the radio and the press the public was informed of the preparations made, the measures being taken and co-operation sought regarding the inoculation cam- paign and the practice of hygiene in the home.
87. Two suspected cases of cholera were reported on the 16th of August, one a gravely ill child with typical symptoms of cholera who was brought into a hospital in the New Territories from an isolated village on the shores of Deep Bay. The other was an elderly woman brought in dead to the Kowloon Public Mortuary from a junk anchored off Cheung Sha Wan. Bacteriological confirmation of the presence of vibrio cholerae of the Ogawa group was available by mid-day on August 17th and Hong Kong declared itself infected with cholera and put into full operation the plans to deal with an epidemic,
88. A detailed report is given in the White Paper on the Outbreak of Cholera in Hong Kong which was laid before Legislative Council on the 13th December, 1961. (White Paper, December 1961). Therefore this report will deal mainly with the epidemiological features considered to be of interest.
89. Epidemiological action was based on the fact that cholera vibrios of the Ogawa group had again appeared in Hong Kong after an absence of 15 years. Early on, it was suspected that these virbrios were of the El Tor type and the haemolysis tests in the laboratory, although in conclusive and not clear cut, supported this. However, this differentia- tion is of no importance as far as the treatment of patients and the control of the outbreak is concerned'. (Pollizter 1959). The densely overcrowded foreshores, the aggregations of squatter and roof top dwellings and the inadequately sanitated old tenement areas in the
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urban areas all presented a very grave risk of an explosive epidemic. Accordingly, the disease was notified to World Health Organization as cholera and appropriate action taken.
90. The outbreak lasted until the 23rd of September when the last but one confirmed case was admitted to hospital. There was then an interval of just over six weeks when one further confirmed infection came to light on routine investigation of a case of moderately severe gastro-enteritis admitted to hospital on the 8th of November. Since that time, routine sub-culture of all specimens sent to the laboratory from cases of gastro-enteritis has been continued, so far with entirely negative findings.
91. The total of proved vibrio cholerae infections was 130 of which 70 were admitted to hospital with clinical symptoms and a further 7 were brought in dead to the Public Mortuaries. The other 53 proved infections, all in persons without symptoms. were found amongst the 731 contacts of clinical cases who were isolated at the Chatham Road Quarantine Centre. Of the 70 patients treated in hospital & died, making a total of 15 deaths during the outbreak.
92. All of the clinical cases encountered were sporadic, were in persons of the Chinese race, and none of these clinical cases could be traced to either a previous clinical case, a known carrier or a clearly defined common source of infection. The contact carriers were all directly related to the respective clinical cuses, being either members of the family or common habitation dwellers. The highest attack rate was in the boat people which accounted for 30% of the proved infec- tions in a group which constitutes only 4.42% of the total population, The contact carrier rate was 25% amongst the hoat people but only 3% amongst those living on land. This is not surprising as the families living in sampans and junks use the boats as permanent dwellings, are of a low socio-economic group and live under very simple and primitive conditions.
93. The greatest number of clinical cases admitted on any one day between the 16th August and the 23rd September was eight, with fifty- two cases occurring during the first twelve days. From the 28th August onwards, there was a gradual decrease, 19 cases occurring over the next twelve days and only five between the 10th and the 23rd of September. Thirty-two cases were notified in Kowloon, 24 in the New Territories and 20 on Hong Kong Island,
94. Of the clinical cases 35% of those treated on Hong Kong Istand presented symptoms and signs indistinguishable from classical cholera;