Abstract
ObjectiveThe purpose of this study is to analyze the positive rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid testing (NAT), cases of and deaths due to SARS-CoV-2, and the epidemiological characteristics of SARS-CoV-2 to identify high-risk populations.MethodsA retrospective study in Jiulongpo district of Chongqing was conducted by performing continuous observations of the frequency of SARS-CoV-2 NAT, analyzing the data of close contacts of patients and asymptomatic carriers, and collecting epidemiological data. Data were collected from January 20, 2020, when the first case of SARS-CoV-2 infection was reported, to March 26, 2020. Descriptive statistical analysis and Cochrane–Mantel–Haenszel analysis were used to compare the positive detection rates and positive diagnostic rates of different exposure groups.ResultsA total of 7,118 people received 10,377 SARS-CoV-2 nucleic acid tests in one district, and the SARS-CoV-2 positive rates were 0.40% (18/4446) and 0.15% (4/2672) in people receiving one and ≥ two nucleic acid tests (p = 0.06), respectively. Those with suspected cases (12.35%) and close contacts (8%) had higher positive rates than people tested at fever clinics (0.39%) (p < 0.001). The median latency (range) of cases was 5 (2, 9) days, and the median time from diagnosis to recovery was 22 (14, 25) days. One recovered patient received a positive test result at 28 days after recovery when she attempted to donate blood. Six clustered cases, including one patient who died, indicated persistent human-to-human transmission. One patient who was diagnosed after death was found to have infected 13 close contacts. People working in catering and other public service departments (36.36%) and people who are unemployed and retirees (45.45%) have an increased risk of infection compared with technical staff (9.09%) and farmers (9.09%).ConclusionThe total positive rate was low in the tested population, and more effective detection ranges should be defined to improve precise and differentiated epidemic control strategies. Moreover, in asymptomatic carriers, SARS-CoV-2 tests were positive after recovery, and patients with suspected SARS-CoV-2 infection who die may pose serious potential transmission threats.
Highlights
In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China
There were enough residents and cases in the target district; 1.2 million people permanently resided in the surveyed district and over 20 cases of COVID-19 were diagnosed
This study found that the positive rates of NAT were different among different high-risk populations
Summary
In December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China. With the spread of SARS-CoV-2, causing the coronavirus disease 2019 (COVID-19) epidemic, cases were identified in other locations in China and many other countries worldwide. As of March 26, 2020, there were 82,034 confirmed cases and a total of 3,293 deaths nationwide in China; 50,006 cases were from Wuhan, according to the official website of the National Health Commission of the People’s Republic of China (http://www.nhc.gov.cn/). At the end of February, the SARS-CoV-2 epidemic was successfully contained through public health interventions such as case detection, isolation, and movement restrictions [4]; new cases have not been reported since February 26, 2020, according to the statistics of the Chongqing Municipal Health Commission (http://wsjkw.cq.gov.cn/). After the start of the pandemic, the Chinese government released pandemic control policies under a “unanimous nationwide system” to joint defense and control by multiple departments [6]
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