COVID-19 exposure in SARS-CoV-2-seropositive hospital staff members during the first pandemic wave at Strasbourg University Hospital, France

Abstract

Objectives: Strasbourg University Hospital faced an important COVID-19 first wave from early March 2020. We performed a longitudinal prospective cohort study to describe clinical and virological data, exposure history to COVID-19, and adherence to strict hygiene standards during the first pandemic wave in 1497 workers undergoing a SARS-CoV-2 serological test at our hospital, with a follow up of serology result three months later.

Patients and methods: A total of 1497 patients were enrolled from April 6 to May 7, 2020. Antibody response to SARS-CoV-2 was measured, and COVID-19 exposure routes were analyzed according to SARS-CoV-2 serological status.

Results: A total of 515 patients (34.4%) were seropositive, mainly medical students (13.2%) and assistant nurses (12.0%). A history of COVID-19 exposure in a professional and/or private setting was mentioned by 83.1% of seropositive subjects (P<0.05; odds ratio [OR]: 2.5; 95% confidence interval [CI]: 1.8-3.4). COVID-19 exposure factors associated with seropositive status were non-professional exposure (OR: 1.9, 95% CI: 1.3-2.7), especially outside the immediate family circle (OR: 2.2, 95% CI: 1.2-3.9) and contact with a COVID-19 patient (OR: 1.6; 95% CI: 1.1-2.2). Among professionally exposed workers, systematic adherence to strict hygiene standards was well observed, except for the use of a surgical mask (P<0.05, OR: 1.9, 95% CI: 1.3-2.8). Of those who reported occasionally or never wearing a surgical mask, nurses (25.7%), assistant nurses (16.2%), and medical students (11.7%) were predominant.

Conclusion: Infection of staff members during the first pandemic wave in our hospital occurred after both professional and private COVID-19 exposure, underlining the importance of continuous training in strict hygiene standards.

Keywords: COVID-19 exposure; Healthcare workers; Humoral response; Personal protective equipment; SARS-CoV-2.

Fig. 1

Flow chart of survey recruitment and serum sampling among staff members at Strasbourg University Hospital. Serological screening was performed using two commercial assays: the Biosynex® (COVID-19 BSS IgG/IgM) Lateral Flow Assay (LFA) detecting anti-Spike (S) antibodies and the EDI™ Novel coronavirus COVID-19 IgG ELISA assay detecting the anti-Nucleocapsid protein (N) IgG. Serological testing was first performed between April 6 and May 7, 2020 (V0) and then 3 months later (V1). Anti-S: anti-spike protein; Anti-N: anti-nucleocapsid protein; ELISA: Enzyme-linked immunosorbent assay; HCW: Healthcare workers; LFA: Lateral flow assay.

Fig. 2

Distribution of COVID-19-associated symptoms according to serological status at V0 and SARS-CoV-2 RT-PCR status (positive, negative, or untested). Percentage of subjects of each category reporting each COVID-19-associated symptom. Seropositive and seronegative subjects at V0 are represented by red bars and blue bars, respectively. Within those workers seropositive at V0, individual percentages for those who were SARS-CoV-2-positive, negative by RT-PCR or untested are shown as differing shades of red.

Fig. 3

Associations between prior COVID-19 symptoms and SARS-CoV-2 serological status. Odds ratio of seropositivity for individually reported symptoms. Data are depicted as odds ratios (black circle) and 95% confidence intervals (bars either side). A total of 1227 participants reported COVID-19 symptoms. Among them, 493 were seropositive at V0, while 734 were seronegative at V0. Symptoms included in the survey were: myalgia, shortness of breath or difficulty breathing, fever, asthenia, rhinitis/pharyngitis, cough, headache, anosmia/dysgeusia, diarrhea, other.

Fig. 4

COVID-19 exposure data collection. Among the 1497 workers enrolled in the study, 1224 subjects answered to at least one COVID-19 exposure route (overall exposure). Among them, 1101 subjects answered for each exposure route: COVID-19 professional exposure only (patients or colleagues), COVID-19 non-professional exposure only (family or other exposure in the private sphere), and COVID-19 mixed exposure (both professional and non-professional exposure).

Fig. 5

Associations between COVID-19 exposure and SARS-CoV-2 serological status. Odds ratio of seropositivity following COVID-19 exposure, according to the type of exposure (professional, patient, colleague, non-professional, family, other non-professional exposures), compared to no COVID-19 exposure. Data are depicted as odds ratios (black point) and 95% confidence intervals (bars either side).