Are the Current Guidelines Sufficient to Establish Infection Control Strategies for COVID-19 Related Issues in Hospitals?

Wooyoung Jang; Bongyoung Kim; Eu Suk Kim; Kyoung-Ho Song; Song Mi Moon; Myung Jin Lee; Ji Young Park; Ji-Yeon Kim; Myoung Jin Shin; Hyunju Lee; Hong Bin Kim

doi:10.3346/jkms.2021.36.e343

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Jang, Kim, Kim, Song, Moon, Lee, Park, Kim, Shin, Lee, and Kim: Are the Current Guidelines Sufficient to Establish Infection Control Strategies for COVID-19 Related Issues in Hospitals?

Original Article

Medicine General & Policy

Journal of Korean Medical Science 2021; 36(50): e343.

Published online: 7 December 2021

DOI: https://doi.org/10.3346/jkms.2021.36.e343

Are the Current Guidelines Sufficient to Establish Infection Control Strategies for COVID-19 Related Issues in Hospitals?

Wooyoung Jang^1,^*,^†

, Bongyoung Kim^2,^*

, Eu Suk Kim³

, Kyoung-Ho Song³

, Song Mi Moon⁴

, Myung Jin Lee⁵

, Ji Young Park⁶

, Ji-Yeon Kim⁷

, Myoung Jin Shin⁸

, Hyunju Lee⁹

, Hong Bin Kim³

¹Hanyang University College of Medicine, Seoul, Korea.

²Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Korea.

³Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.

⁴Division of Infectious Diseases, Department of Internal Medicine, Hallym University Sacred Heart Hospital, Anyang, Korea.

⁵Department of Internal Medicine, Inje University Sanggye Paik Hospital, Seoul, Korea.

⁶Department of Pediatrics, Chung-Ang University Hospital, Seoul, Korea.

⁷Department of Infectious Diseases, Seongnam Citizens Medical Center, Seongnam, Korea.

⁸Infection Control Office, Seoul National University Bundang Hospital, Seongnam, Korea.

⁹Department of Pediatrics, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.

Address for Correspondence: Hong Bin Kim, MD, PhD. Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82, Gumi-ro 173beon-gil, Bundang-gu, Seongnam 13620, Republic of Korea. hbkimmd@snu.ac.kr

Equal contributor:

^*Wooyoung Jang and Bongyoung Kim contributed equally to this work.

^†Present status: Senior student of Hanyang University College of Medicine.

Received 8 November 2021 Accepted 3 December 2021

The Korean Academy of Medical Sciences

https://creativecommons.org/licenses/by-nc/4.0/

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

As hospitals cater to elderly and vulnerable patients, a high mortality rate is expected if a coronavirus disease 2019 (COVID-19) outbreak occurs. Consequently, policies to prevent the spread of COVID-19 in hospital settings are essential. This study was conducted to investigate how effectively national and international guidelines provide recommendations for infection control issues in hospitals. After selecting important issues in infection control, we performed a systematic review and analysis of recommendations and guidelines for preventing COVID-19 transmission within medical institutions at national and international levels. We analyzed guidelines from the World Health Organization, Centers for Disease Control and Prevention, European Centre for Disease Prevention and Control, and Korea Disease Control and Prevention Agency. Recent guidelines do not provide specific solutions to infection control issues. Therefore, efforts need to be made to devise consistent advice and guidelines for COVID-19 control.

Graphical Abstract

Keywords: Coronavirus Disease 2019, Hospital, Infection Control, Guidelines

INTRODUCTION

As hospitals are where elderly patients and those with underlying comorbidities are mainly cared for, a high mortality rate is expected if a coronavirus disease 2019 (COVID-19) outbreak occurs in hospitals. Therefore, strict measures to prevent the spread of COVID-19 in hospital settings are crucial.

There are some guidelines to prevent the spread of COVID-19 in hospitals at the national and international levels.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 This study aimed to review whether national and international guidelines provide detailed recommendations to tackle issues with infection control and prevent the spread of COVID-19 in hospitals.

METHODS

We performed a systematic search for controversial issues regarding infection control during the management of patients with COVID-19 in the hospital. Controversial issues and key questions were selected based on discussions with four infectious diseases specialists (B.K., E.S.K., K.H.S., and H.B.K.). The selected issues and subordinate questions are listed in Supplementary Table 1. For the review of domestic and international guidelines, official websites of the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), European Centre for Disease Prevention and Control (ECDC), and Korea Disease Control and Prevention Agency (KDCA) were screened. Guidelines issued between January 1, 2020, and September 30, 2020, were investigated independently by two researchers (W.J. and B.K.), and contents relevant to the selected issues and subordinate questions were extracted (Supplementary Fig. 1). The reviewed guidelines and their official websites are presented in Supplementary Table 2. The contents were rephrased based on consensus among investigators (W.J. B.K., E.S.K., K.H.S., and H.B.K.).

Ethics statement

The study protocol was approved by the Institutional Review Board of the Seoul National University Bundang Hospital (B-2101/660-303). All methods were performed in accordance with these guidelines and regulations.

RESULTS

Infection control measures for the management of COVID-19 patients

As for screening and selective treatment policies, most organizations recommended that patients with COVID-19 symptoms should be treated at a screening clinic. However, no organization provided recommendations for the type of screening that should be used to identify patients who need to visit a screening clinic, nor did any organization specify criteria for permission to enter the general outpatient clinic for patients with fever and/or respiratory symptoms. All organizations suggested educating patients and caregivers about wearing masks in the hospital.

WHO, CDC, and KDCA recommended a single isolated room for preemptive isolation; however, no organization provided recommendations for determining a specific ward for preemptive isolation. Each organization suggested different criteria for removing preemptive isolation; the disappearance of symptoms was recommended by WHO, a single negative polymerase chain reaction (PCR) result was recommended by CDC, and there was no recommendation by KDCA.

As for an isolation policy for patients with confirmed COVID-19, ECDC and KDCA recommended room requirements for isolation, while WHO and CDC had no recommendations. ECDC and KDCA recommended a single negative pressure room, but they recommended organizing a cohort isolation ward for COVID-19 patients in the case of a shortage of negative pressure rooms. All organizations recommended implementing the symptom-based criteria for removing confirmed COVID-19 patients from isolation.

PCR tests, even for patients without symptoms of COVID-19, were recommended by CDC, while other organizations had no recommendations regarding diagnostic testing. In the case of emergency procedures or operations for patients with suspected COVID-19, CDC and KDCA recommended rapid PCR tests for determining the possibility of COVID-19.

On the strategy for hospital care for healthy individuals who come in close contact with an individual in self-quarantine, only CDC suggested providing a preemptive isolation room for such persons. No organization had recommendations for patients who are released from isolation based on the improvement of symptoms but have consistently positive results from the PCR test (Table 1).

Table 1

Infection control measures for the management of COVID-19 patients

Controversial issues and subordinate questions		WHO	CDC	ECDC	KDCA
Screening and selective treatment policy to prevent COVID-19 patients from entering the hospital
	1. System to prevent patients with COVID-19 symptoms from visiting places where other patients	Telemedicine screening	Telemedicine screening	Telemedicine screening	Screening symptoms using online-based survey
	2. Criteria of patients treated at the screening clinic	COVID-19 symptoms	COVID-19 symptoms, epidemiologically relevant	-	COVID-19 symptoms, epidemiologically relevant, recent overseas travel
	3. Screening measure for selecting of patients who need to visit the screening clinic	-	-	-	-
	4. Criteria for permission of entrance to the general outpatient clinic for patients with fever and/or respiratory symptoms	-	-	-	-
	5. Location of the screening clinic	-	Separated area from hospital building	Separated area from hospital building	Separated area from hospital building
	6. Location of the sampling area	-	Separated area from hospital building	Separated area from hospital building, Areas for drive-through sampling	Separated area from hospital building, Areas for drive-through sampling
	7. Isolation rooms in the emergency department for suspected or confirmed patients with COVID-19	-	-	Recommend	Recommend
	8. Education concerning wearing of masks for patients and caregivers in the hospital	Recommend	Recommend	Recommend	Recommend
	9. Regular monitoring of fever and respiratory symptoms of caregivers	-	Recommend	-	-
	10. Other measures to prevent the influx of COVID-19 into the hospital through caregivers and family/acquaintances	Mandate to wear of masks	Restrict visiting and recommend video call	Keeping hand/respiratory hygiene, physical distancing, restrict visiting and recommend video call	Mandate to wear of masks
Preemptive isolation policy for patients with suspected COVID-19
	1. Patients recommended for preemptive isolation	COVID-19 symptoms	COVID-19 symptoms, epidemiologically relevant	-	COVID-19 symptoms, epidemiologically relevant
	2. Room for preemptive isolation	Single isolated room	Single isolated room	-	Single isolated room
	3. Ward for preemptive isolation	-	-	-	-
	4. Preemptive isolation strategy if the number of suspected patients exceeds the hospital's capacity	Grouping patients by symptoms in the same place (with keeping physical distance each other)	Isolate in general ward (with keeping physical distance each other)	-	-
	5. Criteria for removing preemptive isolation	Disappearance of symptoms (regardless of PCR results)	Single negative PCR result	-	-
	6. Measures for close family members and caregivers of suspected patients during preemptive isolation	-	Restrict entering hospital	-	Restrict entering hospital
Isolation policy for patients with confirmed COVID-19
	1. Room for isolation of patients with COVID-19	-	-	Single room with negative pressure	Single room with negative pressure
	2. Existence of separate isolation ward for patients with COVID-19	-	-	Organize cohort isolation ward if the number of patients exceeds the capacity	Organize cohort isolation ward if the number of patients exceeds the capacity
	3. Type of isolation room in the case of shortage of negative pressure room due to the increase of patients with COVID-19	-	-	Single room without negative pressure	Single room without negative pressure
	4. Designated routes that minimize contact with suspected or confirmed COVID-19 patients	-	Recommend	-	Recommend
	5. Criteria for removing the isolation for confirmed COVID-19 patients	Symptom-based criteria^a	Symptom-based criteria^a	Symptom-based criteria^a	Symptom-based criteria^a
PCR test for patients without symptoms of COVID-19
	1. Range of performing PCR test for patients without symptoms and/or epidemiologically relevance of COVID-19	-	Prior to admission or surgical procedure in closed facility	-	-
Strategy for procedures or operations for patients with suspected or confirmed COVID-19
	1. Policy for detecting cases of COVID-19 infection before emergent procedures or operations	-	Recommend rapid PCR test	-	Recommend rapid PCR test
	2. Decision-making process for operations or procedures in patients suspected of COVID-19 in an emergent situation	-	-	-	-
	3. Infection control policy in the operating room during the treatment of confirmed or suspected COVID-19 patients	Perform procedures in an adequately ventilated room	Avoid AGP	Environmental disinfection using sodium hypochlorite after procedures	Perform procedures in an adequately ventilated room, environmental disinfection using sodium hypochlorite after procedures
Strategy for hospital care for close contacts during self-quarantine period
	1. Allocation of rooms in case of hospitalization	-	Preemptive isolation room	-	-
	2. Elective procedures or operations policy	Perform procedure after the self-quarantine period, but perform it wearing proper PPE in emergent situation	Perform procedure after the self-quarantine period, but perform it wearing proper PPE in emergent situation	Perform procedure after the self-quarantine period, but perform it wearing proper PPE in emergent situation	Perform procedure after the self-quarantine period, but perform it wearing proper PPE in emergent situation
Strategy for hospital care for patients whose symptoms have improved and released from isolation but COVID-19 PCR results are still positive
	1. Allocation of rooms in case of hospitalization	-	-	-	-
	2. Elective procedures or operations policy	-	-	-	-

COVID-19 = coronavirus disease 2019, WHO = World Health Organization, CDC = Centers for Disease Control and Prevention, ECDC = European Centre for Disease Prevention and Control, KDCA = Korea Disease Control and Prevention Agency, PPE = personal protective equipment, PCR = polymerase chain reaction, AGP = aerosol-generating procedure.

^aSymptom-based criteria for discontinuing transmission-based precautions; - Patients with mild to moderate illness who are not severely immunocompromised: (1) At least 10 days have passed since symptoms first appeared, (2) At least 24 hours have passed since last fever without the use of fever-reducing medications, and (3) Symptoms (e.g., cough, shortness of breath) have improved. - Patients with severe to critical illness or who are severely immunocompromised: (1) At least 10 days and up to 20 days have passed since symptoms first appeared, (2) At least 24 hours have passed since last fever without the use of fever-reducing medications, (3) Symptoms (e.g., cough, shortness of breath) have improved, and (4) Consider consultation with infection control experts. - Patients who were asymptomatic throughout their infection and are not severely immunocompromised: (1) At least 10 days have passed since the date of their first positive viral diagnostic test.

Infection control measures for healthcare workers in hospitals

All four organizations recommended an equivalent level of personal protective equipment (PPE) to treat patients suspected or confirmed with COVID-19: N95/high-level respirator, gown, gloves, and eye protector. Only WHO and ECDC recommended using PPE for the disposal of items from patients with confirmed COVID-19. All guidelines did not consistently recommend disinfection or sterilization of N95/KF94 for reuse. CDC and KDCA provided guidance for disinfection or sterilization of powered air-purifying respirator hoods for reuse.

No organization provided guidance for separating healthcare workers who participate in the care of patients with COVID-19 from those who care for general patients. There were also no recommendations for regular monitoring with PCR tests or chest X-rays or a limit on working hours to prevent excessive workloads for healthcare workers who treat patients with COVID-19. Daily screening using the COVID-19 checklist was recommended in all guidelines.

As for work restriction policies, only CDC provided recommendations for work restriction or PCR tests for healthcare workers who have been in contact with COVID-19 patients or had a fever or respiratory symptoms. The criterion for returning to work for healthcare workers with fever or respiratory symptoms was a single negative PCR test in the CDC guideline.

As for the recommendation for activities outside the hospital for healthcare workers, CDC and ECDC provided some guidance, while WHO and KDCA had no guidance (Table 2).

Table 2

Infection control measures for the healthcare workers in the hospital

Controversial issues and subordinate questions			WHO	CDC	ECDC	KDCA
PPE for healthcare workers providing care for COVID-19 patients
	1. PPE for the treatment of patients confirmed with COVID-19		N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector
	2. PPE for the treatment of patients suspected or confirmed with COVID-19: aerosol-producing procedures		N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector
	3. PPE for the treatment and collection of samples from patients suspected of COVID-19		N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector	N95/high-level respirator, gown, gloves, eye protector
	4. PPE for the treatment of patients requiring hospitalization during self-quarantine period		N95/high-level respirator, gown, gloves, eye protection	N95/high-level respirator, gown, gloves, eye protection	N95/high-level respirator, gown, gloves, eye protection	N95/high-level respirator, gown, gloves, eye protection
	5. PPE for the treatment of patients whose symptoms have improved and released from isolation but COVID-19 PCR results are still positive		Not recommend	Not recommend	Not recommend	Not recommend
	6. PPE for disposal of items from COVID-19 confirmed patients		Medical mask, gown, heavy duty gloves, eye protector	-	N95/high-level respirator, gown, gloves, eye protector	-
	7. Education concerning wearing and removing PPE in the hospital		Recommend	Recommend	Recommend	Recommend
Measures to prevent a shortage of PPE
	1. Disinfection or sterilization of N95/KF94 for reuse		Not recommend	Not recommend	Reuse as a last resort	Not recommend
	2. Disinfection or sterilization of PAPR hoods for reuse		-	Disinfect according to the manufacturer’s reuse guidelines	-	Disinfect according to the manufacturer’s reuse guidelines
	3. Replaceable PPE strategy in the case of shortage of PPE for medical staff		Use respirators for an extended time	Use medical masks instead of respirators	Use medical masks instead of respirators	-
	4. Other preventive measures for excessive use of PPE		Recommend telemedicine for mild symptom-patients, use physical barriers to prevent direct contact with patients, minimize number of HCW for treating isolated patients	-	Minimize the use of PPE in cohort isolation wards if the number of patients exceeds the capacity, perform the procedures at once and minimize contact	-
Measures for healthcare workers participating in the care of COVID-19 patients
	1. Separate them from the care of general patients		-	-	-	-
	2. Regular monitoring with PCR tests or CXR		-	-	-	-
	3. Limit working hours to prevent excessive workloads		-	-	-	-
	4. Screen with the COVID-19 checklist		Recommend	Recommend	Recommend	Recommend
Work restriction Policy for healthcare workers
	1. Work restriction and/or performing PCR tests on healthcare workers who have visited high-risk areas of COVID-19 but have no clear epidemiological relations		-	-	-	-
	2. Work restriction and/or performing PCR tests on healthcare workers who have been in contact with COVID-19 patients prior to confirmation		-	Recommend both if they did not use proper PPE	-	-
	3. Existence of plans for the lack of healthcare workers due to the quarantine within the hospital		-	Recommend for establishment of plans	-	-
	4. Work restriction and/or performing PCR tests on healthcare workers who have fever or respiratory symptoms		-	Recommend both	-	-
		- When to perform PCR test	-	As soon as symptoms are recognized	-	-
		- The conditions for returning to work	(Confirmed COVID-19)	Single negative PCR result	-	-
		- The conditions for returning to work	10 days after isolation or 3 days after being asymptomatic	Single negative PCR result	-	-
		- Active surveillance policy after returning to work	-	Self-monitoring after returning to work, wearing mask	-	-
Recommendation for activities outside the hospital for healthcare workers
	1. Existence of restrictions on certain activities outside the hospital		-	Keep social distancing, avoid visiting high-risk areas	Keep social distancing, use own car to commute, use separate room at home if they perform high-risk group care	-

COVID-19 = coronavirus disease 2019, WHO = World Health Organization, CDC = Centers for Disease Control and Prevention, ECDC = European Centre for Disease Prevention and Control, KDCA = Korea Disease Control and Prevention Agency, PPE = personal protective equipment, HCW = health care worker, PAPR = powered air-purifying respirator, PCR = polymerase chain reaction, CXR = chest X-ray.

DISCUSSION

As for the screening and selective treatment policy, there were no guidelines on the criteria for permission to enter a general outpatient clinic. Since the COVID-19 pandemic began, many hospitals have been operating outdoor screening clinics for managing patients with suspected COVID-19 symptoms, such as fever and respiratory symptoms.18 However, screening clinics are equipped with minimal facilities and a workforce that can only provide a minimal examination. Therefore, many hospitals often care for patients with fever and respiratory symptoms who are unlikely to have COVID-19 in the general outpatient clinic because screening clinics have difficulty providing careful evaluation and management. There might be differences among hospitals regarding criteria for permission to enter general outpatient clinics due to the lack of clear guidance on this issue.

A single-center study conducted in South Korea found that 350 suspected COVID-19 cases, defined by symptom and epidemiological associations, were preemptively isolated, and none of them were confirmed with COVID-19.19 Based on the result of this study, both WHO and CDC guidelines, which suggested that isolation can be discontinued if there are no symptoms or if the PCR test is negative, seem appropriate. After all, both WHO and CDC guidelines might be used only in the low possibility of confirmation, such as no close contact with COVID-19 patients.

CDC recommended PCR tests for screening of COVID-19 even for hospitalized patients without COVID-19-related symptoms. The proportion of asymptomatic patients among COVID-19 cases was about 20–30%, and viral shedding also occurred in such patients; there have been concerns about spreading COVID-19 by asymptomatic patients.20 21 22 According to the Infectious Diseases Society of America, the prevalence of COVID-19 among asymptomatic individuals is < 1 to 10%, and considering results of missing a diagnosis of COVID-19 and the sensitivity of the PCR tests, screening for asymptomatic patients is expected to be effective in regions with more than 2% prevalence.23 A study conducted in long-term care facilities in the United States showed that the prevalence of COVID-19 in facilities that performed broad preemptive PCR tests on inpatients was 0.5%, which was significantly lower than 28.0% in facilities that did not perform them.24 This result supports the effectiveness of PCR screening on asymptomatic inpatients.

There were no guidelines for patients who were released from isolation despite a positive PCR test. Although the probability of the existence of infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is very low after 10 days from the onset of COVID-19 symptoms in most cases, patients who are severely ill or immunocompromised could transmit infectious virus particles even after 10 days.25 26 27 28 29 Therefore, there have been concerns about the possibility of spreading COVID-19 from hospitalized patients who were released from isolation despite a positive PCR test, especially those who need aerosol-generating procedures.28 30 31 32 Given that the cut-off values for quantitative RT-PCR and quantitative immunoassays tend to be correlated with infectivity of COVID-19, some researchers have suggested that certain cut-off values could be used as a surrogate marker for the decision to release hospitalized patients from isolation.28 33 34 Further research is needed to determine clear test-based criteria that can guarantee the lack of infectivity of the virus.

Regarding strategies for healthcare workers, there were many recommendations on PPE, but few guidelines for the management of healthcare workers. More specific recommendations are required for patients and healthcare workers because outbreaks in medical institutions could also be spread by medical personnel.35 In addition, there are various reports that healthcare workers in charge of managing patients with COVID-19 are complaining of psychological distress and being exposed to the risk of infection; thus, recommendations to prevent burnout are also needed.36 37

There were some potential limitations to this study. Recommendations on key topics might have been updated since then. First, guidelines from only four organizations were reviewed due to linguistic limitations. Second, we reviewed WHO, CDC, ECDC, and KDCA guidelines in September 2020. Even though there have been no critical changes of recommendations on key topics, some significant newly introduced recommendations have been found in revised guidelines until November 2021 (Supplementary Table 3). Given that the average incubation period of COVID-19 is 4 to 5 days after exposure to SARS-CoV-2, CDC currently recommends performing a second PCR test to remove preemptive isolation and return to work for the persons with a higher level of suspicion for COVID-19.38 Moreover, since mRNA vaccines against COVID-19 showed significant efficacy, CDC currently suggests preemptive isolation and PCR tests only for unvaccinated patients if they have no symptoms.39 However, as it has been confirmed that the effectiveness of the vaccine decreases over time, further consideration of the validity period of the vaccine is needed.40

In conclusion, the current guidelines are not yet concrete and uniform enough to be applied to hospital settings, and there is a lack of clear guidelines on controversial vital topics that need to be considered in real medical situations. Therefore, it is necessary to develop recommendations that can be applied to hospital settings after an analysis based on clinical experiences and discussion with experts.

ACKNOWLEDGMENTS

We would like to thank Kurt B. Stevenson for his inestimable and generous contribution.

Notes

Funding: This work was supported under the framework of the international cooperation program managed by the National Research Foundation of Korea (2020K2A9A1A0109507911).

Disclosure: The authors have no potential conflicts of interest to disclose.

Author Contributions:

Conceptualization: Kim B, Kim ES, Song KH, Kim HB.
Data curation: Jang W, Kim B.
Formal analysis: Jang W, Kim B.
Funding acquisition: Kim HB.
Investigation: Jang W, Kim B.
Methodology: Jang W, Kim B, Kim ES, Song KH, Kim HB.
Project administration: Kim B, Kim ES, Song KH, Kim HB.
Resources: Kim B, Kim ES, Song KH, Moon SM, Lee MJ, Park JY, Kim JY, Shin MJ, Lee H, Kim HB.
Software: Jang W, Kim B.
Supervision: Kim HB.
Validation: Kim B, Kim ES, Song KH, Kim HB.
Visualization: Jang W, Kim B.
Writing - original draft: Jang W.
Writing - review & editing: Kim B.

References

1. World Health Organization (WHO). Advice on the use of masks in the context of COVID-19: interim guidance. Updated 2020. Accessed May 14, 2021. https://apps.who.int/iris/handle/10665/332293 .

2. World Health Organization (WHO). Rational use of personal protective equipment for coronavirus disease 2019 (COVID-19): interim guidance. Updated 2020. Accessed May 14, 2021. https://apps.who.int/iris/handle/10665/331215 .

3. World Health Organization (WHO). Infection prevention and control during health care when novel coronavirus (nCoV) infection is suspected: interim guidance. Updated 2020. Accessed May 14, 2021. https://www.who.int/publications/i/item/10665-331495 .

4. World Health Organization (WHO). Clinical management of COVID-19: interim guidance. Updated 2020. Accessed May 14, 2021. https://apps.who.int/iris/handle/10665/332196 .

5. World Health Organization (WHO). Criteria for releasing COVID-19 patients from isolation: scientific brief. Updated 2020. Accessed May 14, 2021. https://apps.who.int/iris/handle/10665/332451 .

6. Centers for Disease Control and Prevention (CDC). Interim infection prevention and control recommendations for healthcare personnel during the coronavirus disease 2019 (COVID-19) pandemic. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control-recommendations.html .

7. Centers for Disease Control and Prevention (CDC). Return to work criteria for healthcare personnel with SARS-CoV-2 infection (interim guidance). Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/return-to-work.html .

8. Centers for Disease Control and Prevention (CDC). Interim U.S. Guidance for risk assessment and work restrictions for healthcare personnel with potential exposure to SARS-CoV-2. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/guidance-risk-assesment-hcp.html .

9. Centers for Disease Control and Prevention (CDC). Framework for healthcare systems providing non-COVID-19 clinical care during the COVID-19 pandemic. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/framework-non-COVID-care.html .

10. Centers for Disease Control and Prevention (CDC). Performing broad-based testing for SARS-CoV-2 in congregate correctional, detention, and homeless service settings. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/broad-based-testing.html .

11. Centers for Disease Control and Prevention (CDC). Interim guidance on testing healthcare personnel for SARS-CoV-2. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/testing-healthcare-personnel.html .

12. Centers for Disease Control and Prevention (CDC). Responding to SARS-CoV-2 infections in acute care facilities. Updated 2020. Accessed May 14, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/responding-acute-care-facilities.html .

13. European Centre for Disease Prevention and Control. Infection prevention and control and preparedness for COVID-19 in healthcare settings. Updated 2020. Accessed May 14, 2021. https://www.ecdc.europa.eu/en/publications-data/infection-prevention-and-control-and-preparedness-covid-19-healthcare-settings .

14. Korea Disease Control and Prevention Agency (KDCA). Guidelines for the management of medical institutions with confirmed coronavirus infections-19 (for local government). Updated 2020. Accessed May 14, 2021. https://www.kdca.go.kr/board/board.es?mid=a20507020000&bid=0019 .

15. Korea Disease Control and Prevention Agency (KDCA). Coronavirus infectious disease-19 response guidelines (for medical institutions). Updated 2020. Accessed May 14, 2021. https://www.kdca.go.kr/board/board.es?mid=a20507020000&bid=0019 .

16. Korea Disease Control and Prevention Agency (KDCA). Guidance on the operation of a screening clinic for coronavirus infections. Updated 2020. Accessed May 14, 2021. https://www.kdca.go.kr/board/board.es?mid=a20507020000&bid=0019 .

17. Korea Disease Control and Prevention Agency (KDCA). Coronavirus infections-19 prevention and control of infections in medical institutions (for hospital-level medical institutions). Updated 2020. Accessed May 14, 2021. https://www.kdca.go.kr/board/board.es?mid=a20507020000&bid=0019 .

18. Kim JE, Lee JH, Lee H, Moon SJ, Nam EW. COVID-19 screening center models in South Korea. J Public Health Policy. 2021; 42(1):15–26. PMID: 33087849.

19. Shi HJ, Lee JB, Choi MK, Jang YR, Cho YK, Eom JS. Protection and response of a tertiary hospital in South Korea to the COVID-19 outbreak. Disaster Med Public Health Prep. 2021; 15(1):e1–e5.

20. Buitrago-Garcia D, Egli-Gany D, Counotte MJ, Hossmann S, Imeri H, Ipekci AM, et al. Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: a living systematic review and meta-analysis. PLoS Med. 2020; 17(9):e1003346. PMID: 32960881.

21. Bai Y, Yao L, Wei T, Tian F, Jin DY, Chen L, et al. Presumed asymptomatic carrier transmission of COVID-19. JAMA. 2020; 323(14):1406–1407. PMID: 32083643.

22. Kim SE, Jeong HS, Yu Y, Shin SU, Kim S, Oh TH, et al. Viral kinetics of SARS-CoV-2 in asymptomatic carriers and presymptomatic patients. Int J Infect Dis. 2020; 95:441–443. PMID: 32376309.

23. Hanson KE, Caliendo AM, Arias CA, Hayden MK, Englund JA, Lee MJ, et al. Infectious diseases society of America guidelines on the diagnosis of COVID-19: molecular diagnostic testing. Updated 2020. Accessed September 27, 2021. https://www.idsociety.org/practice-guideline/covid-19-guideline-diagnostics/ .

24. Telford CT, Onwubiko U, Holland DP, Turner K, Prieto J, Smith S, et al. Preventing COVID-19 outbreaks in long-term care facilities through preemptive testing of residents and staff members - Fulton County, Georgia, March–May 2020. MMWR Morb Mortal Wkly Rep. 2020; 69(37):1296–1299. PMID: 32941413.

25. Centers for Disease Control and Prevention (CDC). Ending isolation and precautions for people with COVID-19: interim guidance. Updated 2021. Accessed September 27, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/duration-isolation.html .

26. Cheng HY, Jian SW, Liu DP, Ng TC, Huang WT, Lin HH, et al. Contact tracing assessment of COVID-19 transmission dynamics in Taiwan and risk at different exposure periods before and after symptom onset. JAMA Intern Med. 2020; 180(9):1156–1163. PMID: 32356867.

27. Wölfel R, Corman VM, Guggemos W, Seilmaier M, Zange S, Müller MA, et al. Virological assessment of hospitalized patients with COVID-2019. Nature. 2020; 581(7809):465–469. PMID: 32235945.

28. Bullard J, Dust K, Funk D, Strong JE, Alexander D, Garnett L, et al. Predicting infectious severe acute respiratory syndrome coronavirus 2 from diagnostic samples. Clin Infect Dis. 2020; 71(10):2663–2666. PMID: 32442256.

29. Arons MM, Hatfield KM, Reddy SC, Kimball A, James A, Jacobs JR, et al. Presymptomatic SARS-CoV-2 infections and transmission in a skilled nursing facility. N Engl J Med. 2020; 382(22):2081–2090. PMID: 32329971.

30. Liu WD, Chang SY, Wang JT, Tsai MJ, Hung CC, Hsu CL, et al. Prolonged virus shedding even after seroconversion in a patient with COVID-19. J Infect. 2020; 81(2):318–356.

31. Korea Centers for Disease Control & Prevention Division of Risk Assessment and International Cooperation. Findings from investigation and analysis of re-positive cases. Updated 2020. Accessed September 27, 2021. https://www.cdc.go.kr/board/board.es?mid=a30402000000&bid=0030 .

32. National Center for Infectious Diseases. Chapter of infectious disease physicians of the Academy of Medicine of Singapore. Period of infectivity to inform strategies for de-isolation for COVID-19 patients. Updated 2020. Accessed September 27, 2021. https://www.ams.edu.sg/view-pdf.aspx?file=media%5c5556_fi_331.pdf&ofile=Period+of+Infectivity+Position+Statement+(final)+23-5-20+(logos).pdf .

33. La Scola B, Le Bideau M, Andreani J, Hoang VT, Grimaldier C, Colson P, et al. Viral RNA load as determined by cell culture as a management tool for discharge of SARS-CoV-2 patients from infectious disease wards. Eur J Clin Microbiol Infect Dis. 2020; 39(6):1059–1061. PMID: 32342252.

34. Krupp K, Madhivanan P, Perez-Velez CM. Should qualitative RT-PCR be used to determine release from isolation of COVID-19 patients? J Infect. 2020; 81(3):452–482.

35. Lan FY, Wei CF, Hsu YT, Christiani DC, Kales SN. Work-related COVID-19 transmission in six Asian countries/areas: a follow-up study. PLoS One. 2020; 15(5):e0233588. PMID: 32428031.

36. Shreffler J, Petrey J, Huecker M. The impact of COVID-19 on healthcare worker wellness: a scoping review. West J Emerg Med. 2020; 21(5):1059–1066. PMID: 32970555.

37. Park SY, Kim B, Jung DS, Jung SI, Oh WS, Kim SW, et al. Psychological distress among infectious disease physicians during the response to the COVID-19 outbreak in the Republic of Korea. BMC Public Health. 2020; 20(1):1811. PMID: 33246426.

38. Xin H, Li Y, Wu P, Li Z, Lau EHY, Qin Y, et al. Estimating the latent period of coronavirus disease 2019 (COVID-19). Clin Infect Dis. Forthcoming. 2021; DOI: 10.1093/cid/ciab746.

39. Polack FP, Thomas SJ, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine. N Engl J Med. 2020; 383(27):2603–2615. PMID: 33301246.

40. Thomas SJ, Moreira ED Jr, Kitchin N, Absalon J, Gurtman A, Lockhart S, et al. Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine through 6 months. N Engl J Med. 2021; 385(19):1761–1773. PMID: 34525277.