Tracing Asymptomatic SARS-CoV-2 Carriers Among 3674 Hospital Staff

Background: Asymptomatic carriers were positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) without developing symptoms, which might be a potential source of infection outbreak. Now factories and enterprises in Wuhan are gradually resuming production. The asymptomatic infected population should be paid more attention to reduce the possibility of novel coronavirus disease (COVID-19) second outbreak. Methods: In our hospital, 3674 hospital staff have received throat swab RT-PCR test, plasma COVID-19 IgM/IgG antibodies test and chest CT examination. We analyzed the correlation between infection rates and gender, age, job position, work place and COVID-19 knowledge training of the staff. After that, all asymptomatic staff were re-examined weekly for 3 weeks. Findings: In this single-center case series involving 126 hospital staff with abnormal findings, the proportion of asymptomatic infection accounted for 0.76% (28/3674). IgM antibody was detected in 26 cases, and IgG antibody in 73 cases. The lung CT images showed typical findings with ground-glass in 40 cases. Of all staff with abnormal findings, the older they are, the more likely they are to be the staff with abnormal results, regardless of their gender. Of 3674 hospital staff, the positive rate of labor staff is obviously higher than that of health care workers (HCWs) and administrative staff (P 0.05). The positive rate of HCWs who participated in the COVID-19 knowledge training was lower than those did not participate in early training (P 0.05). During 3 weeks follow-up, all asymptomatic patients did not present the development of clinical symptoms or radiographic abnormalities after active intervention in isolation point. Interpretation: To ensure the safety of resumption of work, institutions should conduct COVID-19 prevention training for staff and screening for asymptomatic patients, and take quarantine measures as soon as possible in areas with high density of population. Funding Statement: This work was supported by the Key Project for Anti-2019 novel Coronavirus Pneumonia from the Ministry of Science and Technology, China (grant number 2020YFC0845500), and Wuhan Emergency Technology Project of COVID-19 epidemic, China (grant number 2020020201010013). Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study was approved by the institutional ethics board at Zhongnan Hospital of Wuhan University (No. 2020074) and all participants signed their consent.