Post-lockdown SARS-CoV-2 nucleic acid screening in nearly
ten million residents of Wuhan, China
Results
There were 10,652,513 eligible people aged ≥6 years in Wuhan
(94.1% of the total population). The nucleic acid screening was completed in 19
days (from May 14, 2020 to Jun 1, 2020), and tested a total of 9,899,828
persons from the 10,652,513 eligible people (participation rate, 92.9%). Of the
9899,828 participants, 9,865,404 had no previous diagnosis of COVID-19, and
34,424 were recovered COVID-19 patients.
The screening of the 9,865,404 participants without a
history of COVID-19 found no newly confirmed COVID-19 cases, and identified 300
asymptomatic positive cases with a detection rate of 0.303 (95% CI
0.270–0.339)/10,000. The median age-stratified Ct-values of the asymptomatic
cases were shown in Supplementary Table 1. Of the
300 asymptomatic positive cases, two cases came from one family and another two
were from another family. There were no previously confirmed COVID-19 patients
in these two families. A total of 1174 close contacts of the asymptomatic
positive cases were traced, and they all tested negative for the COVID-19.
There were 34,424 previously recovered COVID-19 cases who participated in the
screening. Of the 34,424 participants with a history of COVID-19, 107 tested
positive again, giving a repositive rate of 0.310% (95% CI 0.423–0.574%).
Virus cultures were negative for all asymptomatic positive
and repositive cases, indicating no “viable virus” in positive cases detected
in this study.
All asymptomatic positive cases, repositive cases and their
close contacts were isolated for at least 2 weeks until the results of nucleic
acid testing were negative. None of detected positive cases or their close
contacts became symptomatic or newly confirmed with COVID-19 during the
isolation period. In this screening programme, single and mixed testing was
performed, respectively, for 76.7% and 23.3% of the collected samples. The
asymptomatic positive rates were 0.321 (95% CI 0.282–0.364)/10,000 and 0.243
(95% CI 0.183–0.315)/10,000, respectively.