AUTHOR=Liang Xiaohua , Sun Yajun , Xiao Lun , Ren YanLing , Tang Xian 

TITLE=The Positive Rate of Nucleic Acid Testing and the Epidemiological Characteristics of COVID-19 in Chongqing

JOURNAL=Frontiers in Medicine

VOLUME=Volume 8 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2021.802708

DOI=10.3389/fmed.2021.802708

ISSN=2296-858X

ABSTRACT=Objective To analyze the positive rate of novel coronavirus (SARS-CoV-2) nucleic acid tests (NATs), the suspected death cases survey and the epidemiology characteristics of COVID-19, and illustrate the high-risk population.
Methods A prospective study in Jiulongpo District of Chongqing was used to conduct continuous medical observations on the frequency of COVID-19 NATs, quarantine close contacts of cases and asymptomatic carries, and collect epidemiological data.
Results 7118 people have received 10 377 SARS-CoV-2 NATs in Jiulongpo District, and the positive rates of COVID-19 were 0.40% (18/4446) and 0.15% (4/2672) in people with once and ≥ twice NATs (P=0.06), respectively. Suspected cases (12.35%) and close contact (8%) have higher positive rates than people from Fever Clinics (0.39%) (P<0.001). The median latency of cases were 5 (2, 9) days and the median time from diagnose to rehabilitation was 22(14, 25) days. The NATs was positive in one recovery case after 28 days from rehabilitation and she was found at donating blood. Six clustered cases including one death communicator indicate persistent human-to-human transmission. One death communicator diagnosed after death infected 13 close contacts. People work in catering and other public services departments or people who are unemployed or retirees have more chance to be infected. 
Conclusion 
The total positive rate is low in the tested population, and a more effective detection ranges should be defined to increase the positive detection rate. Moreover, asymptomatic carrier, SARS-CoV-2 turned positive after rehabilitation and dead suspected cases may have serious potential threaten.