HEALTH
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wells in the urban areas and vigorous inspection of public eating places, food premises, markets and hawkers. Particular attention was paid to the collection and disposal of nightsoil and to sam- pling of nightsoil for bacteriological examination. All inoculation centres were re-opened for cholera immunization and just over one million doses of vaccine were given during the outbreak.
It was possible to conduct a detailed epidemiological investiga- tion of each case that occurred and the results were consistently baffling. Specimens of foodstuffs in the infected premises were all cultured and were all negative for cholera. Positive swabs were, however, obtained from certain of the latrine buckets, from a chopping block used for the preparation of food in one instance and in several cases from water in kitchen drains and on floors. One roof tank used for flushing a water closet yielded vibrios but the well which supplied the tank was negative.
On the night of 10th September the first specimen to give a positive culture from a tanker vehicle containing communal night- soil was obtained. This was in the course of routine random sampling and afterwards all tankers in use in the urban areas of Kowloon and Hong Kong Island were sampled nightly. Within the next 10 days positive cultures of cholera vibrios were obtained from tankers serving 12 collection routes in Kowloon and 10 districts on the Island. It was possible in three cases to trace the infection back through the hoppers serving the tankers to latrine buckets used in tenements. One bucket came from a communal latrine and further investigation was not possible. However, in the two other cases, one in a tenement and the other in a rooftop squatter community, rectal swabs were obtained from the residents. All these swabs proved negative.
On 8th October, no case having occurred since 20th September, the Colony was declared free of infection. Five days later another case of cholera was confirmed in a fishing village in the Yuen Long district in the New Territories. In view of the fact that vibrios had disappeared from communal nightsoil in the urban areas, and that this particular village community could be readily controlled from a quarantine point of view, only the district of Yuen Long was declared infected.
Epidemiological investigations again revealed a very interesting situation. The community, consisting of 410 people, were all
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