The effectiveness of active surveillance measures for COVID-19 cases in Pudong New Area Shanghai, China, 2020.

The aim of this study was to thoroughly document the effects of multiple intervention and control methods to mitigate the ongoing coronavirus disease 2019 (COVID-19) outbreak in Pudong New Area, Shanghai. After identification of the first confirmed case of COVID-19 in Pudong on January 21, 2020, the local Center for Disease Control and Prevention (CDC) launched a case investigation involving isolation, close-contact (CC) tracing and quarantine of persons with a potential exposure risk to prevent and control transmission. Epidemiological features of cases detected by three different strategies were compared to assess the impact of these active surveillance measures. As of February 16, 2020, a total of 108 confirmed COVID-19 cases had been identified in Pudong, Shanghai. Forty-five (41.67%) cases were identified through active surveillance measures, with 22 (20.37%) identified by CC tracing and 23 (21.30%) by quarantine of potential exposure populations (PEPs). The average interval from illness onset to the first medical visit was 1 day. Cases identified by CC tracing and PEPs were quarantined for 0.5 and 1 day before illness onset, respectively. The time intervals from illness onset to the first medical visit and isolation among actively screened cases were 2 days (p = .02) and 3 days (p = .00) shorter, respectively, than those among self-admission cases. Our study highlights the importance of active surveillance for potential COVID-19 cases, as demonstrated by shortened time intervals from illness onset to both the first medical visit and isolation. These measures contributed to the effective control of the COVID-19 outbreak in Pudong, Shanghai.