key: cord-351022-8y43jhmu
authors: Schwartz, Carmela; Oster, Yonatan; Slama, Carole; Benenson, Shmuel
title: A dynamic response to exposures of healthcare workers to newly diagnosed COVID-19 patients or hospital personnel, in order to minimize cross transmission and need for suspension from work during the outbreak
date: 2020-09-01
journal: Open Forum Infect Dis
DOI: 10.1093/ofid/ofaa384
sha: 
doc_id: 351022
cord_uid: 8y43jhmu

BACKGROUND: During the corona virus disease (COVID-19) epidemic, many healthcare workers (HCWs) were exposed to infected persons, leading to suspension from work. We describe a dynamic response to exposures of HCWs at the Hadassah Hospital, Jerusalem, to minimize the need for suspension from work. METHODS: We performed an epidemiological investigation following each exposure to a newly diagnosed COVID-19 patient or HCW; close contacts were suspended from work. During the course of the epidemic, we adjusted our isolation criteria according to the timing of exposure related to symptoms onset, use of personal protective equipment and duration of exposure. In parallel, we introduced universal masking and performed periodic SARS-CoV-2 screening for all hospital personnel. We analyzed the number of HCWs suspended weekly from work and those who subsequently acquired infection. RESULTS: In the 51 investigations conducted during March-May 2020, we interviewed 1095 HCWs and suspended 400 (37%) from work, most of them, 251 (63%), during the first two weeks of the outbreak. The median duration of exposure was 30 minutes (IQR, 15-120). Only 5/400 (1.3%) developed infection, all in the first two weeks of the epidemic. After introduction of universal masking and despite loosening the isolation criteria, none of the exposed HCWs developed COVID-19. CONCLUSIONS: Relatively short exposures of HCWs, even if only either the worker or the patient wore a mask, probably poses a very low risk for infection. This allows us to perform strict follow-up of exposed HCWs in these exposures, combined with repeated testing, instead of suspension from work.

As of May 2020, Israel has experienced more than 19,000 cases of coronavirus disease (COVID-19) (1777 cases/million) and more than 300 deaths (33 deaths/million) (1) .

Jerusalem and its surroundings is the area with the highest prevalence of COVID-19 patients in Israel (2) .Health care workers (HCWs) are at increased risk of exposure to infected persons (3) , and concern aroused early in the course of the epidemic that a substantial number of HCWs might need to be suspended from work. This could seriously affect the functioning work force available at the hospital (4) (5) .

Understanding of the mode of transmission of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), and strict guidelines for personal protective equipment (PPE) during direct patient contact and any interactions between HCWs in the hospital, are essential for ensuring staff protection and safety (6) . Furthermore, immediate epidemiological investigation and, if needed, early suspension from work of exposed HCWs is needed in order to limit the spread of infection to and between HCWs and patients (7) (8) .

In this research, we describe the outcomes of our dynamic response to exposures of HCWs to newly diagnosed positive patients or personnel, aimed at minimizing infection of HCWs and cross transmission during the COVID-19 outbreak. (Supplementary table) . Especially at the beginning of the epidemic, in the second week of March, many health care workers (HCWs) were exposed to COVID-19 patients, in the hospital or outside. Immediate epidemiological investigations of exposed HCWs were initiated, in order to break the chain of cross-transmission between HCWs as well as avoiding transmission from HCWs to patients, thus keeping maximal work force available.

A c c e p t e d M a n u s c r i p t 7

The IPC team got a notice of any positive COVID-19 HCW or patient in the hospital, either from the Ministry of Health (in a few hours after positive test results) or automatically from the hospital laboratory through the computerized information system (immediately upon verification of a positive test). In order to identify every possibly exposed HCW, a thorough epidemiological investigation was initiated immediately, even during evening shifts and weekends. The IPC team interviewed every such HCW and recorded the exact circumstances and duration of the encounter.

We defined close contact as exposure of at least 15 minutes, in proximity of less than two meters, to a positive COVID-19 person (9) . In case of a contact of less than one meter, we considered even five minutes of exposure as a close contact. According to the Centers for Disease Control (CDC) guidelines (10), wearing of PPE by the index case and/or the exposed HCW should be taken into consideration when deciding upon the need for home isolation of the exposed HCW. If both the index case and the HCW wore a facemask (surgical mask or N95 respirator), there was no need for isolation. The same decision was applied if the index case did not wear a facemask but the HCW wore a facemask and a face shield (Table 1) .

During the course of the epidemic and the evolving understanding of the infectivity and transmission of SARS-CoV-2, we adjusted our criteria for home isolation of exposed HCWs (Supplementary table) . During the first two weeks of the epidemic in Israel, all exposed HCWs meeting the criteria for close contact were suspended from work for 14 days. After two weeks (on March 20), during which over 250 HCWs were sustained from work, the need A c c e p t e d M a n u s c r i p t 8 for home isolation was redefined according to the following principles: 1) if the index case was symptomatic at the time of exposure (e.g., fever or chills, respiratory symptoms, loss of smell or taste), all close contacts were sent to home isolation for 14 days following exposure date.

2) If the exposure occurred more than four days before the index case developed symptoms, since most patients are only infective within four days prior to symptoms (11), isolation was not required. 3) If the exposure occurred four days or less before the index case developed symptoms (if the index case never had symptoms, than within four days before the positive SARS-CoV-2 test), isolation was required for ten days since the last exposure and return to work was approved after a negative nasopharyngeal PCR test on day ten (12) . These principles are summarized in Table 2 . We asked every exposed HCW to inform us immediately in case of any evolving symptoms. Needless to say that every exposed employee who developed any suspicious symptoms was tested for the presence of SARS-CoV-2, and suspended from work while the results were pending. After relieve of symptoms and a negative test result, the employee was allowed back to work.

In the beginning of the epidemic in Israel (March 2020), we recommended the use of PPE for direct contact with suspected or positive COVID-19 patients, according to the CDC and Israeli ministry of Health guidelines at that time (13-14). COVID-19 positive patients were isolated in the designated wards and all HCWs entering the area wore full airborne isolation PPE, e.g. waterproof gown, gloves, N95 respirator, face shield and head cover. Patients with suspected COVID-19, according to symptoms or because of exposure to a positive person, were put in isolation rooms and HCWs entered the room while wearing surgical mask, face A c c e p t e d M a n u s c r i p t 9 shield, disposable gown and gloves. In these patients, in case of severe respiratory symptoms or aerosol producing procedures, PPE was upgraded to full airborne protection as described above. In the light of many exposed HCWs, during the last week of March 2020, the IPC team required the use of surgical masks by hospital personnel during every patient contact. In addition, staff meetings were restricted to ten attendees and allowed only while adhering to rules of social distancing, and interaction between staff during shifts was kept to a minimum. In parallel, a routine periodic screening program for SARS-CoV-2 of all HCWs was introduced at the hospital (15) . This included summoning all employees for PCR testing for SARS-CoV-2 performed on nasopharyngeal swabs. The employees were asked to undergo a second test after five days. Periodic screening of all HCWs is continues at the hospital until these days. On April 7, we changed our policy to universal masking of HCWs and visitors at all times and of patients during any contact with a HCW.

We used descriptive statistics for all investigations performed on HCWs who were exposed to a COVID-19 patient or colleague and their outcomes. Categorical variables are presented with percentages and continuous variables are presented with median and inter-quartile range (IQR). We describe the number of HCWs suspended weekly from work and those subsequently acquiring infection over the course of the epidemic. Additionally, we examined the input of the changing strategies of PPE and criteria for suspension from work on these outcomes. We used Extended Mantel-Haenszel test to compare the rates of HCWs that we sent to home isolation in each investigation, before and after the demand for A c c e p t e d M a n u s c r i p t 01 masking of HCWs (WinPepi version 11.60). Significance was two tailed and determined at p<0.05.

Between March 8 and May 23 (11 weeks), we performed 51 exposure investigations. In 23/51 (45%) the index case was a HCW and in 28/51 (55%) a patient (emergency department, 8 (29%); delivery room, 7 (25%); medical, 8 (29%); surgical, 3 (11%); outpatient clinics, 2 (7%)). In five out of these exposure investigations (10%), the index case was asymptomatic throughout the course of his disease. Altogether, we interviewed 1095 HCWs (Table 3) . Out of these, 400 (37%) HCWs had close contact as defined by the CDC (10). Most of these were relatively short exposures (median 30 min, IQR, 15-120). In most of these exposures, either the HCW and/or the index case were not fully protected as defined by the CDC guidelines (both without a mask, 360 (90%); only one with a mask, 36 (9%); both masked but exposure greater than three hours, 4 (1%)). These workers were suspended from work and sent to home isolation. The vast majority of HCWs, 251/400 (63%) were sent to home isolation during the first two weeks of the outbreak. Of all HCWs sent to home isolation following these investigations, only 5/400 (1.3%) developed infection with COVID-19 during the period of isolation, all at the very beginning of the epidemic (Graph). None of the HCWs investigated because of potential exposure, but not sent to isolation, had developed COVID-19.

Since our hospital performed routine screening for SARS-COV-2 on all HCWs, we were able to check and ascertain that we did not miss any positive HCW whom we might not have March 22, no HCW who was exposed after this change was infected until the end of the study period (Graph).

Healthcare workers are at increased risk of acquiring COVID-19 from unrecognized patients or colleagues during work (16) (17) . At the very beginning of the epidemic in Israel, the IPC team of our hospital started epidemiological investigations of every exposure to a newly diagnosed SARS-CoV-2 positive patient or HCW. The first investigations resulted in the need to suspend a large number of HCWs from work, requiring home isolation. Serious concern aroused that departments would need to be totally shut down, threatening the ability of the hospital to keep functioning over time. As soon as we learned in mid-March 2020 from the CDC guidelines at that time, that wearing PPE (facemask with or without face shield) could reduce the need for excluding exposed HCWs from work (14), we updated our rules of protection. We introduced universal masking for hospital personnel, patients and visitors and social distancing between HCWs. Later on, this approach was suggested also in the literature (6) . Since then, the number of HCWs whom we needed to suspend from work decreased significantly. As shown in the graph, this decline happened while the epidemic in Israel was still on the rise. A single report from Minnesota department of Health, USA, also showed a reduction in HCWs infections in the Hospital following the introduction of universal masking (18) . In addition, and according to new accumulating knowledge, we redefined the criteria for suspension from work and duration of isolation required (14) . We differentiated between exposures to symptomatic or asymptomatic index cases and reduced the duration of home isolation needed after exposure to an asymptomatic index case. Since 95% of exposed people who become infected, do so within 10 days from exposure, we performed SARS-CoV-2 nasopharyngeal test on day 10 for isolated workers, prior to allowing them to return to work (12) . By that, we further reduced the number of HCWs excluded from work at a given time.

During 51 epidemiological investigations performed, out of 1095 potentially exposed HCWs whom we thoroughly interviewed, we defined 400 as close contacts, prompting suspension from work. Out of these, only five developed clinical signs of infection with SARS-CoV-2, all in the early phase of the COVID-19 outbreak. Although we narrowed the criteria for isolation, none of the HCWs investigated, but not isolated, developed clinical signs of infection with COVID-19. Owing to the periodic universal screening of all HCWs performed at our hospital, we were assured that there were no eventual asymptomatic HCWs among those investigated or isolated. Additionally, the proactive screening allowed us to assume that we probably did not miss any close contact during our investigation process, who potentially could become positive.

Furthermore, the results of this study raises the question whether the criteria for isolation were still too rigorous, since, after the initial phase, none of the HCWs excluded from work developed COVID-19. In the light of these findings, and in the presence of universal masking and social distancing, it might be worth to consider substitution of suspension from work of exposed HCWs by rigorous follow-up of symptoms together with repeated testing on days A c c e p t e d M a n u s c r i p t 03 five and ten after exposure. This approach was recently studied in a mathematical model performed by .

There are some limitations to this study: Due to the retrospective nature of epidemiological investigations, there is a recall bias and hence, in some cases it was not trivial to define each contact unequivocally. Our criteria for home isolation after exposure may need further specification. Accumulating knowledge on the infectivity of asymptomatic or presymptomatic patients might shed light on this issue (20) . In addition, despite periodic screening of all HCWs, since we did not test them every day, we still might have missed asymptomatic positive personnel; however, we assume that the chance for that is negligible. Our experience might be valid in hospitals with dedicated COVID-19 departments and universal masking, and we assume that this by now is the standard of care in most countries.

In conclusion, after introducing universal masking for HCWs, patients and visitors, and social distancing, none of the exposed HCWs developed COVID-19. Based on the results of our study, we assume that relative short exposures of HCWs, even if only either the worker or the patient wore a mask, probably poses a very low risk for infection. This allows us to consider performing strict follow-up of exposed HCWs for symptoms, together with repeated PCR testing, instead of suspending them from work. A c c e p t e d M a n u s c r i p t Figure 1 

About: Israeli Government: Ministry of Health

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All authors report no conflict of interest.

Our study does not include factors necessitating patient consent.

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