key: cord-0814273-nyr5b7up
authors: Li, Guozhen; Hu, Caiying; He, Qiong; Liu, Jing; Xiong, Nian; Wang, Haizhou
title: Apparent and occult infections of medical staff in a COVID-19 designated hospital
date: 2020-07-14
journal: J Infect Public Health
DOI: 10.1016/j.jiph.2020.07.005
sha: ae4c83f549408949046cecd7d1b95fde25c2c24d
doc_id: 814273
cord_uid: nyr5b7up

Since the outbreak of novel coronavirus (SARS-CoV-2)-infected pneumonia (COVID-19), numerous medical staff are fighting on the frontline. However, the possibility of occult infection in medical staff is ignored in many recent studies. Herein, we collected data in a COVID-19 designated hospital from January 22, 2020 to March 10, 2020. A total of 33 medical staff had at least one nucleic acid test of throat swab, immunoglobulin G (IgG) or IgM serum antibody test, and chest computed tomography (CT), were enrolled. Finally, we identified 25 cases (75.8%) were isolated for hospitalized treatment after positive virus detection. In addition, 4 cases who were all negative for nucleic acid test detection with no clinical symptoms, and none of their chest CT were abnormal. However, the results of serum IgG or IgM antibody test in these 4 cases were positive, suggesting the presence of occult infection. In conclusion, data from our single center indicated that SARS-CoV-2 had a high medical infection rate (29/33 = 87.9%) and might have a potential risk of occult infection.

Since December 2020, novel coronavirus (SARS-CoV-2)-infected pneumonia (COVID-19) occurred in Wuhan, and rapidly spread throughout China [1, 2] . Recently studies mainly focused on infections in patients, while little attention has been paid to the apparent and occult infections in medical staff.

Since the outbreak of COVID-19, Wuhan Red Cross Hospital was designated as the hospital for fever and COVID-19 on January 22, 2020. As of March 10, 2020, 33 staff had at least one nucleic acid test of throat swab for SARS-CoV-2, IgG-IgM combined serum antibody test for SARS-CoV-2, and chest computed tomography (CT) to screen potential infections.

The swab virus nucleic acid was detected by the RT-PCR assay method according to the manufacturer's protocol (Shanghai BioGerm Medical Technology Co.,Ltd) [3] . The blood antibody was detected by the point-of-care lateral flow immunoassay method according to the manufacturer's protocol (Shenzhen Yahuilong Biological Technology Co.,Ltd) [4] . The antibody test was reported with a reliable sensitivity of 88.66% and specificity of 90.63% [4] .

This study was approved by the ethics committee of Wuhan Red Cross Hospital, and written informed consents were obtained. Table 1 showed the basic information of the included subjects. In brief, all medical staff worked in different departments, whereas they shared the same access to and from work. The 33 medical staff had an average age of 38.1 years (range: 25~56) and an average work duration of 13.9 days (range: 1~40) in the isolation ward ( Fig. 1) .

Among these staff, 25 people (75.8%) were isolated for hospitalized treatment after positive virus detection.

Among the 8 staff with negative virus detection, 4 subjects were hospitalized for fever or respiratory symptoms. Other 4 subjects were asymptomatic, and chest CT scan showed no abnormalities.

The 4 medical staff are still working in the frontline because they do not meet the present diagnostic criteria [5] . As of March 10, they all had 48 days' work experience in the isolation ward. Case 1 was a 34-year-old nurse who had a positive detection for IgG, whereas a negative detection for IgM. Case 2 was a 45-year-old doctor. Case 3 was a 39-year-old doctor. Case 4 was a 48-year-old support staff. These 3 cases had a positive detection for IgM, whereas a negative detection for IgG. In this study, although all cases undergo protection training before taking up their posts, our data indicate that COVID-19 is a highly contagious disease. There may be two reasons. First, due to a lack of understanding of the epidemiology of SARS-CoV-2 in January, several medical staff might be infected due to insufficient protection and in an incubation period before the hospital was converted into the COVID-19 designated hospital. Second, the hospital itself was a comprehensive hospital, and its transformation into a designated hospital might not completely meet the requirements of hospital for infectious disease. Therefore, even with strictly protective 

In summary, data from our single center indicated that SARS-CoV-2 had a high medical infection rate (29/33 = 87.9%) and might have a potential risk of occult infection.

Funding: This work was supported by grants 2016YFC1306600 (to NX) and 2018YFC1314700 (to NX) from the National Key R&D Program of China, grants 81873782 (to NX) from the National Natural Science Foundation of China.

GZL, CYH, JL and QH collected the data. GZL, NX and HZW prepared and revised the manuscript. GZL, NX and HZW were responsible for summarizing all data related to this study. 

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Similarity in Case Fatality Rates (CFR) of COVID-19/SARS-COV-2 in Italy and China

Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in Wuhan

Development and Clinical Application of a Rapid IgM-IgG Combined Antibody Test for SARS-CoV-2 Infection Diagnosis

National Health Commission of the People's Republic of China. Diagnosis and treatment protocols of the novel coronavirus pneumonia

Chest CT for Typical 2019-nCoV Pneumonia: Relationship to Negative RT-PCR Testing

Occult infection of SARS was found in Heyuan, Guangdong

Covert infection of severe acute respiratory syndrome in health-care professionals and its relation to the workload and the type of work