Cholera case investigation and the detection and treatment of cholera carriers in Hong Kong.

Between 1961 and 1966 cholera cases occurred in Hong Kong in each year except 1965. During this period each case was extensively investigated in order to detect carriers among the contacts.In 1961 investigations were confined to the home of the patient but it was found that a much more extensive investigation was required to get epidemiological information of real value. From 1962 onwards the investigations were extended to include the patient's place of employment or school and any eating-place visited by the patient in the 7 days before the onset of disease.Detection of carriers has been a relatively simple procedure in Hong Kong as it has been the policy to isolate all contacts of a cholera case in a quarantine centre. In 1961 three rectal swabs were taken to detect carriers; this was increased to 5 in 1962 and now 7 consecutive daily swabs are considered necessary. Oral streptomycin is regarded as the best treatment for carriers because it is relatively cheap, it produces no side-effects, treatment can be completed in one day and vibrio resistance to the drug is unlikely.As detailed case investigation is expensive, however, it should be undertaken only if the object is to determine the source of the infection. This object was achieved in Hong Kong on only 6 occasions during the period under review. Isolation of the contacts was of little value in comparison with the disruption of family life and the expense involved. Although regular nightsoil sampling was a good indicator of the presence of the disease, the back-tracing of positive samples occupied facilities and staff which could have been better used in case investigation.