key: cord-0797990-woyycghi
authors: Basso, Trude; Nordbø, Svein Arne; Sundqvist, Erik; Martinsen, Tom Christian; Witsø, Eivind; Wik, Tina S.
title: Transmission of infection from non-isolated patients with COVID-19 to health care workers
date: 2020-08-20
journal: J Hosp Infect
DOI: 10.1016/j.jhin.2020.08.015
sha: 8373545164c8ed4f1726bd27c4d09a925504913a
doc_id: 797990
cord_uid: woyycghi

Insufficiently protected health care workers (HCWs) defined as high-risk contacts of patients with COVID-19 are routinely quarantined. This study evaluated transmission of infection from a symptomatic patient with COVID-19 to 60 HCWs exposed ≤2 m for ≥15 minutes, or during aerosol generating procedures. Following ≥106 unique high-risk contacts, none of the HCWs tested positive for SARS-CoV-2 RNA or had developed antibodies. The HCWs reported adherence to basic infection control procedures. These results were in accordance with other reports and should reassure HCWs and further stimulate a broader evaluation of the foundation for the current practice of home-quarantine of non-symptomatic HCWs.

During the Coronavirus Disease-19 (COVID-19) pandemic, the proportion of health care workers (HCWs) amongst verified, infected individuals, has been reported somewhere between 10 and 20 % [1, 2] . In addition, a considerable proportion of HCWs with COVID-19 self-report to have been infected at work [1, 3] . An objective evaluation of the risk for HCWs contracting the new coronavirus (SARS-CoV-2) compared to the general population is difficult since test criteria for HCWs differ from that of the general population.

An increasing number of reports indicate low rates of SARS-CoV-2-transmission from non-isolated patients to HCWs [4] [5] [6] [7] [8] [9] . It is interesting that the incidence of asymptomatic cases amongst HCWs in a hospital showed the same trend of virus transmission as the general community and dropped following social distancing despite the hospital remaining full of patients with COVID-19 [10] .

Our level 1 trauma center received transfer of a middle-aged patient with a pelvic injury from a hospital in a region with a low prevalence of COVID-19. The patient had mild hypoxia (satO 2 96 % on 3 L O 2 ), but no obvious airway symptoms. The patient was placed in a single occupancy room in a regular ward. The patient was not isolated, but social distancing measures were enforced due to the ongoing pandemic. Hence, mingling with other patients, such as during meals, was prohibited. The room had fresh-air ventilation with three air changes per hour, a hand sink with soap and disinfectants on both sides of the door and once daily cleaning including disinfection of all contact surfaces. The hospital provides clothing which is changed at least once a day for all HCWs. HCWs or patients in our hospital did not, and still at time of writing, do not wear masks on a general basis.

From the day of admittance, the patient experienced intermittent fever and diarrhoea in addition to mild hypoxia (Table I) . On day four the fever increased, and the patient developed a cough with purulent sputum. The patient was isolated the following morning, and two consecutive tests showed high viral loads (Ct values 27.3 and 23.3) of SARS-CoV-2. By then, the patient had undergone two operations under combined general-and epidural anesthesia in an operating theatre with laminar air flow and 50 air-changes per hour. 60 HCWs were quarantined for two weeks due to participation in aerosol-generating procedures (AGPs) with insufficient personal protective equipment (PPE), or close-contact viral exposure defined as ≤2 meters for ≥15 minutes.

The transmission-risk of SARS-CoV-2 from patients to HCWs is a highly relevant issue. It affects not only HCWs, but also how hospitals plan health care services during this pandemic. The aim of this study was to evaluate the extent of SARS-CoV-2 transmission from a symptomatic, non-isolated patient to HCWs in a hospital with adequate capacity.

The study was approved by the Regional Committee for Medical and Health Research Ethics in Mid-Norway (REK 2020/6073). Quarantined HCWs were invited to participate under informed written consent.

The participants were tested for SARS-CoV-2 RNA approximately two weeks after virus exposure. Samples were taken from the retro-tonsillar pharynx according to procedure in a specialized COVID-19 outpatient clinic for hospital employees. RNA was extracted from the samples using an easyMag extractor (bioMérieux) and analyzed with in-house real-time RT-PCR assay targeting the E-gene of SARS-CoV-2 [11] .

To evaluate if any of the exposed HCWs had undergone COVID-19 infection, sera were collected approximately three weeks following exposure for the detection of antibodies against SARS-CoV-2. EDI Novel Coronavirus COVID-19 lgG and IgM ELISA (Epitope Diagnostics, Inc.) was used for initial testing, and supplemented with tests from DiaSorin (LIAISON® SARS-CoV-2 S1/S2 IgG test), Abbott (Alinity i SARS-CoV-2 IgG), Roche (Elecsys Anti-SARS-CoV-2) and Wantai (WANTAI SARS-CoV-2 Ab ELISA).

All participants completed a questionnaire to map the type and extent of virus exposure, symptoms while in quarantine, and self-evaluation of adherence to procedures on hand hygiene. This included hand wash with soap and water or disinfectant, prior to and following procedures in a patient room and direct or indirect contact with a patient.

Fifty-eight out of 60-quarantined HCWs consented to participate in the study. Two HCWs could not be reached in time for testing. One HCW withdrew from the study following the throat swab and all data was excluded, leaving 57 participants for analyses. Fifty-seven HCWs completed an RNA-test, antibody testing and answered the questionnaire.

All participants tested negative for SARS-CoV-2 RNA and SARS-CoV-2 IgM. In addition, all of them tested negative for IgG and total antibodies with tests from 3 out of 5 manufacturers. Discrepant test results are presented in table II. These discrepant, positive, results were reproducible. Twenty-two HCWs (39 %) experienced some airway symptoms during the quarantine, of which a sore throat was most frequently reported (n=12). None of the responders experienced loss of taste and smell. Fifteen HCWs had already been tested during their quarantine because of symptoms, and all tested negative at both test points.

There were ≥106 unique contacts of ≥ 15 minutes of ≤ 2 m, or during AGPs, between HCWs and the nonisolated COVID-19 patient. 19 nurses on the ward had ≥ 46 unique close contacts that also included oral hygiene. Twelve HCWs had been exposed during AGPs: 7 during in-and/ or extubation at ≤ 2 meters from the patient's head, and another five at > 2 meters. 11 HCWs were present during open surgery involving power drilling, electrocautery and pulsed lavage.

Half of the affected HCWs (n=30) had not used any kind of PPE while exposed. Surgical masks were used by 16/57, and by 0/19 of the nurses on the ward. Disposable gloves were used by 35/57 and visor / glasses by 5/57. One HCW reported close contact with the patient during extubation without wearing a surgical mask. The majority (n=40, 70%) were certain they had adhered to the hand hygiene procedure and 16 were quite certain (total 98 %). One HCW reported that it was unlikely that he / she had performed proper hand hygiene.

In this study we found that ≥106 unique close contact exposures, including 12 contacts during AGPs with a nonisolated patient with COVID-19, resulted in no SARS-CoV-2 transmissions from patient to HCWs. With one exception, all included HCWs were certain or quite certain that their adherence to the hand hygiene procedure had been proper at the time of exposure.

Ideally, and according to common practice, samples for PCR-testing should have been collected on day seven and repeated at day 14 following exposure. However, since this study required ethical approval and written J o u r n a l P r e -p r o o f consent it was not possible to organize the study in time for testing during the first week. Nevertheless, this study is, to our knowledge, the first to complement throat swabs with antibody-testing in a prospective study of symptomatic and non-symptomatic HCWs. It must be stressed, however, that even antibody-tests do not seem to reveal all individuals who have been previously infected with COVID-19. Our test results illustrate that antibody tests may give false-positive reactions in a low-prevalence setting and retesting with alternative assays may be required to draw a conclusion.

To our knowledge, six other reports on disease transmission from non-isolated COVID-19 patients to HCWs have been published (table III) . Out of a total of 330 HCWs, five HCWs tested positive for SARS-CoV-2 RNA. Two out of 64 HCWs (3%) that had been exposed during AGPs without wearing a particulate respirator, contracted COVID-19. All these seven reports were from hospitals with seemingly good infection prevention practices.

There were suboptimal COVID-19 screenings both before transfer and upon admission of our patient. The procedure for patient transfer between hospitals was consequently changed from per phone oral clarification, to strict documentation by written questionnaires. The affected ward normally serves as a unit for revision arthroplasties and spinal surgery. At the time of the incident, elective surgeries had been reduced to a minimum and the ward then hosted a broad range of orthopedic patients. Abrupt changes in established means of organizing care of patients, must be considered a risk factor for impaired patient safety. It is likely that the reorganization for the COVID-19 pandemic contributed to the delay in diagnosing this very disease and sending 60 HCW into quarantine.

There is seemingly a low risk of virus transmission from non-isolated COVID-19 patients to HCWs in hospitals with adequate capacity and with HCWs who adhere to basic measures to prevent infectious disease transmission. Our results should reassure HCWs and further stimulate a broader evaluation of the foundation for the current practice of home-quarantine of non-symptomatic HCWs.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-forprofit sectors.

The study was approved by the Regional Committee for Medical and Health Research Ethics in Mid-Norway (REK 2020/6073). 

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