key: cord-0754081-7ai5hgby
authors: Liu, Hanzhao; Ye, Chuchu; Wang, Yuanping; Zhu, Weiping; Shen, Yifeng; Xue, Caoyi; Zhang, Hong; Zhang, Yanyan; Li, Shihong; Zhao, Bing; Xu, Hongmei; Hao, Lipeng; Zhou, Yixin
title: The effectiveness of active surveillance measures for COVID‐19 cases in Pudong New Area Shanghai, China, 2020
date: 2021-02-16
journal: J Med Virol
DOI: 10.1002/jmv.26805
sha: 495a590e9138c1f8e33e8be4568024deac20d57b
doc_id: 754081
cord_uid: 7ai5hgby

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.

already arrived in the Pudong New Area. Moreover, any new arrivals from Hubei Province were screened at every city entrance, including airports, train stations, and so on. All the information of the identified PEPs at city entrances was immediately sent by a big data network to the community in which they lived. PEPs were quarantined under compulsory medical observation at home or centralized facilities for 14 days, and during that time, they were assessed for fever or respiratory symptoms by medical staff twice daily. Persons in quarantine were transferred by ambulance directly to fever clinics when they developed any related symptoms during the quarantine period, while others were released after 14 days without fever and any respiratory symptoms.

Patients transferred by ambulance from centralized facilities or their homes and people with clinical manifestations of COVID-19 who sought medical care on their own were sent to fever clinics immediately when they visited a hospital. According to the COVID-19 case definition in Shanghai, 13 suspected cases were diagnosed and sampled in fever clinics.

Within 2 h, the information of suspected cases was reported online, and specimens were sent to the Pudong Center for Disease Control and Prevention (CDC) for testing by real-time reverse transcriptionpolymerase chain reaction (RT-PCR). Moreover, patients were isolated in the hospital until COVID-19 confirmation and then transferred to a designated hospital for isolation and treatment. The other suspected cases were excluded by two consecutive negative laboratory test results of samples taken at intervals of more than 24 h.

An epidemiological investigation of all suspected cases was conducted by the Pudong CDC within 24 h to identify CCs and collect basic demographics, signs, symptoms, and exposure histories. CCs were identified through contact tracing and defined as those who lived in the same apartment, shared a meal, traveled, or socially interacted, and had close (within 1 m) and prolonged (generally ≥15 min) contact with any suspected COVID-19 patients without effective protection from 2 days before the patient's illness onset to the time of patient isolation. Detailed information of CCs was sent to their communities for further confirmation and management. Similar to PEPs, the CCs were quarantined, but only at centralized facilities for 14 days. The release was conditional on a negative RT-PCR result for the related suspected case or the absence of fever and any respiratory symptoms for 14 days if the related suspected case was confirmed. 

All confirmed COVID-19 cases reported between January 21 and CC management, PEP management, and screening of self-admitted patients in fever clinics. Important intervention dates were plotted to compare intervals from illness onset to quarantine initiation, the first medical visit, isolation, and confirmation.

All statistical analyses were performed using R 3.5.1 (R Core Team, R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria). The χ 2 test or Fisher's exact test was used for categorical variables, and the Wilcoxon rank sum test or Kruskal-Wallis test was used for continuous variables, as appropriate.

p < .05 were considered statistically significant.

Between January 21 and February 16, 2020, the Pudong CDC confirmed 108 COVID-19 cases ( 14 and peaked approximately 1 week later. The epidemic was effectively controlled within 1 month, and no additional cases were identified at the end of February (Figure 2A ).

On average, quarantine was initiated 1 day before illness onset among those with a potential exposure risk and 0.5 days before illness onset among CCs. A total of 52.17% (12/23) of the PEPs and 50.00% (11/22) of the CCs were quarantined before illness onset ( Figure 2B ).

The median intervals from illness onset to the first visit, isolation, and confirmation were 1, 2 and 4 days, respectively. Compared to those of self-admission cases, the intervals from illness onset to the first medical visit, isolation, and confirmation of cases identified from CCs and PEPs were all significantly shorter (p = .02, .00, and .00, respectively; Table 1 and Figure 3 ).

Nearly half of the confirmed COVID-19 cases in the Pudong New Area were detected through active surveillance measures, according to our study. Large proportions of the CCs and potentially exposed individuals were identified and quarantined before the development of symptoms. On average, quarantine was initiated 1 day before the onset of illness among potentially exposed individuals and 0.5 days before the onset of illness among CCs. The time interval from illness onset to isolation for patients identified by active surveillance was significantly shorter than that for self-admitted patients.

At the beginning of the intervention, all of our surveillance measures of monitoring the population with higher infected risk, such as close contacts and travelers from high-risk areas, aimed to identify and isolate them as soon as they became patients. We did not actually consider avoiding presymptomatic transmission at that time. However, with the implementation of the intervention measures, increasing evidence from related research globally had indicated the occurrence of asymptomatic and presymptomatic transmission of COVID-19, 15,16 which increase the necessity of monitoring population with high infectious risk before they became a patient. Our results also showed that a lot of cases had been quarantined before they were detected with SARS-CoV-2.

As the prodromal symptoms are mild and do not begin abruptly, early signs and symptoms of COVID-19 are difficult to recognize. 17, 18 Given the individual differences in the symptoms of this disease as well as subjective and constantly changing symptoms, most patients might not seek prompt medical care when they develop any symptom, especially at the early stage of a pandemic. A lack of timely detection of cases directly leads to an increased risk of community transmission; however, these problems can be averted by active quarantine and compulsory medical observation of the specific population. At the early stage of the COVID-19 outbreak, the proportion of persons who visited a fever clinic within 2 days of illness onset was 65.74% in Pudong New Area, Shanghai, compared with 61% in Gansu Province of China, 19 27% in Wuhan in China, 20 and 23.1% in South Korea. 21 Patients with mild symptoms promptly sought timely medical care, and detection and isolation were performed within a short period, which significantly reduced CC transmission, the risk of community transmission, and the likelihood of a patient developing severe illness. Overall, 74.07% of the patients in our study were isolated within 5 days after illness onset, which is similar to the rate of 68% in Gansu 19 and higher than the rate of 11% in Wuhan at the early stages of the disease. 7 In Singapore, the mean interval from symptom onset to hospital isolation or quarantine was 5.6 days. 22 Routine health management ensured timely case identification and confirmation, effectively protecting additional community members from infection. As a benefit from the positive control T A B L E 1 Characteristics of the confirmed COVID-19 patients in Pudong New Area, Shanghai, January-February 2020 We are currently facing a totally new, extraordinarily complex and highly damaging virus. Active surveillance of cases and management, coupled with identification and quarantine of PEPs and CCs, is an effective strategy and is significantly more effective for preventing infection than travel restrictions and exposure restrictions. 11 These active surveillance measures have been successfully implemented in several countries, including Singapore and South

Korea. Singapore maximized detection of suspected patients and legally supported home quarantine orders for patients with mild illness. 23 South Korea substantially expanded the scope of testing to detect and isolate cases as early as possible. 24 This investigation has two limitations. First, we did not calculate the actual number of cases averted by each of our strategies due to a lack of information from the limited cases. However, previous studies using epidemiological models have demonstrated that early identification of potential cases plays a substantial role in determining whether an outbreak is controllable. 10, 25, 26 Second, the intervention we conducted in

Pudong might need strong policy support from the government and need (A) (B)

COVID-19 coronavirus pandemic

National Health Commission & State Administration of Traditional Chinese Medicine. Diagnosis and treatment protocol for novel coronavirus pneumonia

Estimation of exponential growth rate and basic reproduction number of the coronavirus disease 2019 (COVID-19) in Africa

Pattern of early human-to-human transmission of Wuhan

Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study

Estimates of the reproduction number for seasonal, pandemic, and zoonotic influenza: a systematic review of the literature

Time intervals from illness onset to the first visit, isolation, and confirmation of confirmed COVID-19 cases with different detection methods in Pudong New Area

Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia

Preliminary estimation of the basic reproduction number of novel coronavirus (2019-nCoV) in China, from 2019 to 2020: a data-driven analysis in the early phase of the outbreak

First-wave COVID-19 transmissibility and severity in China outside Hubei after control measures, and second-wave scenario planning: a modelling impact assessment

Modeling the epidemic dynamics and control of COVID-19 outbreak in China

Effect of non-pharmaceutical interventions to contain COVID-19 in China

Epidemiology, causes, clinical manifestation and diagnosis, prevention and control of coronavirus disease (COVID-19) during the early outbreak period: a scoping review

Shanghai Municipal Health Commission & Shanghai Administration of Traditional Chinese Medicine. Prevention and control protocol for novel coronavirus pneumonia of Shanghai (version 4)

Wuhan Municipal People's Government. Notice of Wuhan novel coronavirus infection of lung infection prevention and control headquarters

Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing

Presymptomatic transmission of SARS-CoV-2-Singapore

Epidemiological characteristics of the first 53 laboratory-confirmed cases of COVID-19 epidemic in Hong Kong

Clinical presentation of COVID-19: case series and review of the literature

Epidemiology of coronavirus disease in Gansu Province, China, 2020

Active case finding with case management: the key to tackling the COVID-19 pandemic

Clinical course and outcomes of patients with severe acute respiratory syndrome coronavirus 2 infection: a preliminary report of the first 28 patients from the Korean cohort study on COVID-19

Evaluation of the effectiveness of surveillance and containment measures for the first 100 patients with COVID-19 in Singapore

COVID-19 in Singapore-current experience: critical global issues that require attention and action

How is COVID-19 affecting South Korea? What is our current strategy? Disaster Med Public Health Prep

Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts

How Shenzhen, China avoided widespread community transmission: a potential model for successful prevention and control of COVID-19

Strengthening public health at the community-level in China

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