Corona Virus Disease 2019 (COVID-19) originated in Wuhan, China has caused many healthcare workers (HCWs) infected. Seventy-two HCWs manifested with acute respiratory illness were retrospectively enrolled to analyze the risk factors. The high-risk department, longer duty hours, and suboptimal hand hygiene after contacting with patients were linked to COVID-19.
We conducted a retrospective cohort study among the HCWs (>18 years of age) with acute respiratory symptoms in a single-center setting, who worked at the forefront to fight against COVID-19 since it outbroke. To define the cohort, all participants were clinicians and nurses from a designated hospital. The designated Hospital is a 3300-bed grade-A tertiary hospital serving for the medical treatment in this outbreak. The case with acute respiratory symptoms was defined by any or multiple of the present symptoms like cough, fever, brachypnea, chest distress, headache, hemoptysis, others related to acute respiratory illness,and diarrhea, testing with radiologic characters and laboratory evidence. All participants were given informed consent.
HCWs in different departments were divided into two groups based on risk exposure. High-risk exposure was defined as the high-risk department (HRD) with interventional medical or surgical procedures that generate respiratory aerosols, including the respiratory department, infection department, ICU and surgical department. Other low-risk clinical departments were regarded as general groups (GD). Diagnosed cases of SARS-CoV-2 infection was identified as outcome variables. The follow-up was ended on Jan 28 because all HCWs were confirmed with COVID-19 infection or non-infection. HCWs were required to fulfill an online questionnaire giving detailed information on sociodemographic characteristics, time to symptomatic progression, contact history, medical practice, hand hygiene, and proper personal protective equipment (PPE) (Appendix 1). A total of 83 questionnaires were collected, of which 72 were valid, with an effective rate of 86.75%
The outcome variable was regarded as diagnosed COVID-19, which is defined according to “The diagnosis of COVID-19 conformed to Diagnosis and treatment of novel coronavirus pneumonia (Trial Version 3)” issued by the National Health Commission of the People’s Republic of China. All cases were diagnosed with the test by PCR nucleic acid. The novel coronavirus nucleic acid was detected by real-time fluorescence RT-PCR, and the virus gene was sequenced, which was highly homologous with the known new coronavirus.
1. Baseline of sociodemographic characteristics
Of these 72 people, 39 were classified in GD and 33 in HRD. Ages ranged from 21 to 66 years with a median (interquartile range, IQR) of 31 (28-40,12). The median (IQR) of daily work was 8 (8-10, 2) hours (Table 1). Before the cohort started, subject baseline characteristics were compared. Gender (χ2=2.243, P =0.134), types of HCWs (χ2=0.076, P =0.782), and age (35.24 versus 37.98, P =0.579) were generally well-balanced between the exposed and non-exposed group.
2. Common symptoms
Common symptoms were fever (85.71%), cough (60.71%), brachypnea (7.14%), chest distress (7.14%), headache (7.14%), diarrhea (7.14%), and hemoptysis (7.14%) among the 28 HCWs diagnosed with COVID-19.
Table 2 demonstrated that diagnosed family member (DFM), diagnosed patient (DP) and suspected patient (SP) were related to infections of HCWs, separately with the relative risk of 2.76 (95% CI = 2.02-3.77, P<0.01), 0.36 (95% CI = 0.22-0.59, P<0.01), and 0.49 (95% CI = 0.27-0.89, P<0.05).
4. Medical operation and protection
Illustrated in Table 2, the relative risks and their 95% confidence intervals of unqualified hand-washing, suboptimal hand hygiene before and after contact with patients, and improper PPE were 2.64 (95%CI = 1.04-6.71, P<0.05), 3.10 (95%CI = 1.43-6.73, P<0.01), 2.43 (95%CI = 1.34-4.39, P<0.01), and 2.82 (95%CI = 1.11-7.18, P<0.05), respectively.
5. HRD and GD
It was indicated that the HRD group had 2.13 times higher risk in developing COVID-19 compared with the GD group (crude RR =2.13, 95%CI: 1.45-3.95, P<0.05). After a stratified analysis with the Mantel-Haenszel method to adjust confounding factors, gender (RRHM= 3.08, 95%CI: 1.09-8.71, P homogeneity = 0.70), type of HCWs (RRHM= 3.56, 95%CI: 1.29-9.84, P homogeneity = 0.27), and gender * type of HCWs (RRHM= 2.85, 95%CI: 1.03-7.90, P homogeneity = 0.25) showed a homogeneity between layers.
6. Effect interaction
The interaction effect between exposure and other factors was conducted with logistic regression. It revealed that : 1) male + HRD (RR=2.45, 95%: 1.38-3.45, P<0.01) with control for HCW; 2) clinician + HRD (RR=2.00, 95%: 1.03-2.89, P<0.05) with control for gender; and 3) unclean hand after contact with patients (UHA) + HRD (RR=3.07, 95%: 1.14-5.15, P<0.01), UHA + GD (RR=2.45, 95%: 1.45-4.03, P<0.05) , and clean hand +HRD (RR=2.30, 95%: 1.30-3.77, P<0.05) with control for gender and HCW, were significant.
7. Time to event
Figure 1 is a Kaplan-Meier curve of the whole 72 participants in the cohort. It revealed that the cumulative proportion of infection-free would be decreased with daily workhour, which is more obvious in HRD (P<0.05). To be specific, all of the staff in HRD would be infected if they worked 15 hours per day.
HCWs worked in HRD and with suboptimal hand hygiene after contacting patients had a higher risk of COVID-19. Higher risk with longer duty hours was found, especially in HRD. A call to confirm these risk factors in other larger cohorts, as well as work to mitigate these, would be appropriate.
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