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Evaluation of the Effectiveness of Surveillance and Containment Measures for the First 100 Patients with COVID-19 in Singapore — January 2–February 29, 2020

Our take —

In Singapore, implementing aggressive surveillance and containment measures (e.g., compulsory quarantine for all asymptomatic close contacts) for SARS-CoV-2 was associated with a steep drop in the time between symptom onset and case isolation between the beginning of January and the end of February. The results are compelling, but may not be applicable where SARS-CoV-2 is already much more prevalent and where public health institutions are not as robust, as these measures are highly labor-intensive.

Study design


Study population and setting

This study reports on Singapore’s first 100 cases of SARS-nCov-2 between January 1 and February 29, 2020. The majority (72%) of patients were aged 30–59 years (mean age: 42.5 years), and 60% of patients were male. Twenty-four cases were imported, and the rest resulted from local transmission.

Summary of Main Findings

Singapore employed extremely aggressive contact tracing and isolation measures, building on a strong surveillance and testing infrastructure that included routine testing of multiple high-risk patient categories. The containment measures included compulsory quarantine for asymptomatic close contacts, active daily monitoring of all contacts via telephone, and immediate hospitalization of any contact experiencing symptoms. Over half (53%) of confirmed COVID-19 cases were detected via contact tracing. The seven-day moving average of the interval from symptom onset to isolation in hospital or quarantine declined significantly (p<0.001) from the beginning of January to the end of February for both imported (9.0 to 0.9 days) and local (18.0 to 3.1 days) cases.

Study Strengths

Authors used all available clinical reports of confirmed COVID-19 cases. The interval from symptom onset to isolation is a meaningful indicator of the impact of public health interventions to control disease transmission.


Results have limited generalizability, as Singapore’s ability to implement these measures may exceed that which is possible in other countries. The epidemic in Singapore had not yet manifested in institutional clusters (e.g., long-term care facilities or health facilities).

Value added

This analysis is one of the first to demonstrate the benefits of aggressively implemented “traditional” epidemiologic methods to trace contacts and detect cases.