We placed close contacts under quarantine for 14 days from last exposure to the individual with confirmed COVID-19, either at home or at designated government quarantine facilities. We monitored their health status daily; people who developed symptoms were conveyed in dedicated ambulances to hospital for isolation and testing as part of active case-finding. We video-called individuals who were quarantined at home three times a day to verify their location; quarantine violators were tagged with a continuous tracking device. We placed other contacts (depending on risk stratification) on phone surveillance or advised them to self-monitor and visit a primary-care clinic if they became unwell.