key: cord-0738190-uded6zv6
authors: Uçkay, Ilker; Steinwender, Ludwig; Burkhard, Jan; Holy, Dominique; Strähl, Mario; Farshad, Mazda
title: Outcomes of asymptomatic hospital employees in Covid-19-post-exposition quarantine during the 2(nd) pandemic wave in Zurich
date: 2021-04-21
journal: J Hosp Infect
DOI: 10.1016/j.jhin.2021.04.010
sha: 6c969e7aa989e72233a1fb8c8182104b2b986a2d
doc_id: 738190
cord_uid: uded6zv6

nan

During this Covid-19 pandemic, the ultimate goal of prevention is subject of various, previously unknown, administrative recommendations [1, 2] . After the 1 st pandemic wave in spring 2020, health authorities started to promote Contact Tracing by imposing postexposition quarantine for all adults after a close contact to laboratory-confirmed cases; independently of the individual setting. Since then, people with permanent exposure, e.g. living in the same household, or hospital employees with a transient, unprotected contact (e.g. in the cantina) are routinely quarantined for the 5-14 days. However, there are no reallife evaluations regarding the benefit of quarantining hospital employees [3] [4] [5] [6] , while the penury of the staffing serves as an argument to strengthen the measures against the pandemic.

The Balgrist University Hospital in Zurich, Switzerland, is a tertiary center for orthopedic surgery, rheumatology, paraplegic patients and neuro-urology with 1250 employees [2] . We investigated the outcome of quarantined employees and arbitrarily limit our study period to the three most intensive months of the 2 nd pandemic wave between October, 1 st 2020 and December, 31 th 2020 in Zurich. As the primary outcome, we investigated the risk for symptomatic Covid-19 during and after the ten days of quarantine; and stratify the risks according to the nature of exposure. We distinguished between a permanent, or iterative exposure, e.g. in the same family, and a transient, single exposure. As a secondary outcome, we estimate the loss of workdays. We confirmed Covid-19 by PCR. Swiss authorities defined a "close contact" as any unprotected exposure of >15 minutes (or directly to respiratory secretions); within <1.5 meter; occurring within the last two days before the first symptoms.

All asymptomatic employees with close and unprotected contact to a confirmed Covid-19 case were send home for a ten-days' quarantine. We contacted them regularly by phone. In J o u r n a l P r e -p r o o f case of a secondary, symptomatic Covid-19 disease with a corresponding PCR results, we were informed. The Human Resources, Occupational Medicine, and Infection Control established databases that we use for this study (Ethical Committee; BASEC 2021-00119).

We investigated 376 symptomatic episodes among 337 different employees for Covid-19 (101 males; median age 37 years (range, 18-63 y); 11 immune-suppressed) and ordered quarantine for 81 asymptomatic cases. Among all these 81 asymptomatic quarantines waiting at home, only ten (12%) became symptomatic for Covid-19 disease after a median of 5 quarantine-days (range, 3-11 d). Among all 94 Covid-positive episodes (nosocomial and community-acquired; 25%) overall, the proportion of those with prior asymptomatic quarantine was 11% (10/94 cases). All post-quarantine Covid-19 cases reported a prior permanent exposure occurring during; family life (n=6), repetitive basketball matches (1), spending the evening with friends at home (1), and regular meals with colleagues at work (2) . In this subgroup of permanent exposures, the risk of symptomatic Covid-19 was high (10/22; 45%). In contrast, no employees with transient exposure reportedly developed symptoms. The quarantine led to an estimated loss of 810 full workdays within three months; or 710 working days among those who remained healthy. The majority of our employees could not work at home. Figure 1 summaries the study flowchart.

During the peak of the 2 nd pandemic wave in Zurich, our hospital employees sent for postexpositional quarantine developed a symptomatic Covid-19 infection only in 12%, while 88% of them simply waited at home. The proportion of Covid-19 episodes for which a quarantine was discussed, represented only 11% of all Covid-19 cases. We mark two types of exposure histories that should be distinguished: transient and permanent exposure. Hospital employees with permanent or iterative exposure, e.g. in the family, may have a higher risk (up to 45%). It J o u r n a l P r e -p r o o f makes sense they stay at home. In contrast, we failed to find a valuable argument in favor of quarantining employees with a unique exposure. The costs for these quarantines were high [1] , both in terms of money and the lack of work power. With our own data, we conclude that the decision for quarantine orders should base on the duration and nature of exposure.

In the literature, little is known about the objective benefit of a post-exposition Covid-19 quarantine among asymptomatic adults. To cite examples, probably only 0.4% of all voyagers returning to Switzerland from designated "quarantine countries" develop symptoms after their arrival [7]. This specific risk was 0.6% for travelers arriving to Bahrain [3] , 2% among healthcare workers (HCW) in Saudi Arabia [4] , or 16% among university students with highrisk contact in Kentucky [6] . Our practice-based evaluation study has two major limitations: i)

We renounced on testing asymptomatic persons, since a negative result did not shorten the quarantine. ii) Our study only concerns the period of the 2 nd peak wave and targets the employees of a tertiary hospital with no dedicated Covid-19 wards [1, 2] . We cannot generalize our findings. Possibly, the medical knowledge among hospital employees is higher than in the general population; allowing a more efficacious prevention.

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No Nosocomial Transmission of SARS-CoV-2 between Healthcare Workers in Surgical Departments Unexposed to Covid-19 Patients

Quarantining arriving travelers in the era of COVID-19: balancing the risk and benefits a learning experience from Bahrain

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COVID-19 Test Strategy to Guide Quarantine Interval in University Student

SARS-CoV-2 seroprevalence and transmission risk factors among high-risk close contacts: a retrospective cohort study

Time from Start of Quarantine to SARS-CoV-2 Positive Test Among Quarantined College and University Athletes -17 States

We are indebted to Mrs. Marie-Helen Suter, Ruth Schwab, Nadja Bragatto, Regula Schüpbach, Tamara Steiner, and to the entire Human Resources Department for their help.

The authors declare that they have no competing interests.

There was no funding necessary. J o u r n a l P r e -p r o o f