key: cord-0917625-8ybembn2
authors: Kolodziej, L.M.; Hordijk, S.; Koopsen, J.; Maas, J.J.; Thung, H.T.; Spijkerman, I.J.B.; Jonges, M.; Bomers, M.K.; Sikkens, J.J.; Jong, de; Zonneveld, R.; Schinkel, J.
title: SARS-CoV-2 transmission risk upon return to work in RNA-positive healthcare workers
date: 2022-03-12
journal: J Hosp Infect
DOI: 10.1016/j.jhin.2022.02.024
sha: f72ad56dfdf92767decaaccb0fe794c4b2b7d98f
doc_id: 917625
cord_uid: 8ybembn2

BACKGROUND: Healthcare workers (HCWs) are at risk for coronavirus disease 2019 (COVID-19) and for spreading Severe Acute Respiratory Syndrome Virus 2 (SARS-CoV-2) amongst colleagues and patients. AIM: We aimed to study presence of SARS-CoV-2 RNA and possible onward transmission by HCWs upon return to work after COVID-19, and association with disease severity and development of antibodies over time. METHODS: Unvaccinated HCWs with positive SARS-CoV-2 RT-PCR were prospectively recruited. Data on symptoms was collected via telephone questionnaires on day 2, 7, 14 and 21 after positive test. Upon return to work, repeat SARS-CoV-2 RT-PCR was performed and serum was collected. Repeat sera were collected at week 4, 8, 12 and 16 to determine antibody dynamics over time. Phylogenetic analysis was conducted to investigate possible transmission events originating from HCW with a positive repeat RT-PCR. FINDINGS: Sixty-one (84.7%) participants with mild-moderate COVID-19 had a repeat SARS-CoV-2 PCR performed upon return to work (median 13 days post symptom onset), of which 30 (49.1%) were positive with a median cycle threshold (Ct) value of 29.2 (IQR 3.0). All HCWs developed antibodies against SARS-CoV-2. No significant differences in symptomatology and presence of antibodies were found between repeat RT-PCR-positive and -negative HCWs. Eleven direct colleagues of six participants with a repeat RT-PCR Ct-value <30 tested positive after the HCW returned to work. Phylogenetic and epidemiologic analysis did not indicate onward transmission through HCW who were SARS-CoV-2 RNA positive upon return to work. CONCLUSIONS: HCWs regularly return to work with sub stantial SARS-CoV-2 RNA loads. However, we found no evidence for subsequent in-hospital transmission.

Healthcare workers (HCWs) play a critical role in the response against the ongoing coronavirus disease 2019 pandemic. Multiple studies show higher infection rates 59 in HCWs compared to the general population, suggesting an occupational risk. [1] [2] [3] As for all 60 confirmed cases, COVID-19 in HCWs requires measures to prevent transmission including 61 quarantine. Hereby, (long) periods of absence can increase the strain on the healthcare system.

During this study, hospital guidelines prescribed that HCWs with confirmed COVID-19 could 63 return to work 24 hours post symptom resolution. National and international guidelines 64 generally recommend a minimal duration of isolation of 7 to 10 days after onset of symptoms and 24 hours to 5 days after improvement or resolution of symptoms. [4] [5] [6] [7] Some 66 guidelines mention the option of re-testing before returning to work for specific occasions 67 (e.g., for HCWs with severe immune deficiencies), [5, 6, 8] but standard re-testing before 68 returning to work is not recommended by any of the other guidelines since the assumed risk 69 of transmission is considered negligible after these time periods. [9, 10] 70 On the other hand, Severe Acute Respiratory Syndrome Virus 2 (SARS-CoV-2) RNA be valuable in determining the risk of transmission upon return to work and subsequent re-85 infection in this population with an increased occupational risk.

The aim of this prospective observational study is to assess the presence of SARS-CoV-2 87 RNA and corresponding cycle threshold (Ct) values upon resolution of symptoms in SARS-

CoV-2 infected HCWs and its relation to disease severity, antibody dynamics and the risk of Hereby the presence of 14 predefined symptoms (coughing, pharyngitis, dyspnoea, rhinitis, 103 abdominal pain, diarrhoea, nausea, vomiting, anorexia, fever, myalgia, headache, fatigue and anosmia or dysgeusia) was determined. Follow-up symptomatology questionnaires were 105 conducted at day 7, 14 and 21, as long as participants reported to experience symptoms.

Repeat nasopharyngeal and oropharyngeal swabs and initial serum were collected when 107 HCWs returned to work. Hospital guidelines for returning to work required that all respiratory 108 symptoms had to be resolved > 24 hours. Anosmia, dysgeusia and fatigue were not required 109 to be resolved upon return to work. Repeat sera were collected at week 4, 8, 12 and 16 after 110 the initial positive RT-PCR. All sera were stored at -20 o C until serological tests were 111 performed.

The nasopharyngeal and oropharyngeal swabs were collected in E-swab or UTM viral 113 transport medium (COPAN Diagnostics, Murrieta, CA, USA). defined as contacts within the same department that tested positive for SARS-CoV-2 within 7 126 days after study participants with a repeat RT-PCR Ct-value <30 returned to work.

The median time between disease onset and time of initial RT-PCR was 1 day (range 1-7).

The median duration of symptoms was 10 days (range 0-41). Symptoms decreased over time 165 (Table II) . Fever and dyspnoea were not frequently reported. At disease onset, rhinitis, 

Risk of COVID-19 among front-line FIGURE LEGENDS Figure 1. Maximum likelihood phylogeny of SARS-CoV-2 sequences with identified potential transmission clusters

A condensed maximum-likelihood phylogeny of SARS-CoV-2 sequences that were collected (marked with tip shapes) and a random sample of contemporaneous reference sequences (no tips) circulating within the Netherlands. Tip shapes are coloured according to the wards the HCWs (circle and square tips) and their within-department-contacts (diamond tips) were working on