Risk of coronavirus disease 2019 transmission in an emergency department with multiple open beds

To the Editor

Hospital emergency departments (EDs) have been on the frontline of coronavirus disease 2019 (COVID-19) care. Screening and triage strategies have been established [1] and isolation zones for patients with suspected COVID-19 have been implemented in EDs. However, real data are limited regarding the risk of transmission of COVID-19 from infected patients in the ED, especially EDs in multiple open beds. Therefore, we evaluated the risk of COVID-19 transmission to healthcare workers (HCWs) and patients or guardians in the ED from patients with COVID-19.

This study was performed in a 2700-bed tertiary-care hospital in Seoul, South Korea; the hospital implemented universal personal protective equipment (PPE) for HCWs in the ED and required all patients and guardians to wear a mask: a surgical or KF94 mask (filtering facepiece 2-equivalent respirator). From January 2020 to March 2021, we conducted contact tracing for patients with confirmed COVID-19 who visited our ED, and we performed whole-genome sequencing (WGS) for suspected transmission cases in the ED. Detailed infection control measures, definition of contact, and method of WGS are shown in the Supplementary Material.

We included 35 patients with COVID-19 in this study, and two of those visited the paediatric ED. The characteristics of the 35 patients are shown in Table 1 . The median number of days from symptom onset to ED visit was 4 days (interquartile range (IQR) 1–7). Twenty-nine patients stayed in open beds or multi-patient rooms, with stays of a median 4.5 hours (IQR 2.75–6). The median lowest cycle threshold (Ct) value among E, RdRp, N genes at diagnosis was 26 cycles. A total of 99 HCWs (16 close and 83 casual contacts) and 242 patients and guardians (42 close and 200 casual contacts) were identified as contacts in the adult ED, and none were identified as contacts in the paediatric ED. The median numbers of close and casual contacts were 0 (0–2) and 3 (0–10).

Table 1.

Patient characteristics (n = 35)

Characteristics	Value
Male	13 (37)
Age (years)	67 (48–73)
Waves in which patients were diagnosed:a
Between 1st and 2nd wave in Korea (From 5th May to 11th August, 2020)	3 (9)
During 2nd wave (from 12th August to 12th November 2020)	6 (17)
During 3rd wave (from 13th November 2020 to now)	26 (74)
Median days from symptom onset to ED visit	4 (1–7)
Staying in an open bed or multi-patient room	29 (83)
Median hours staying in an open bed or multi-patient room	4.5 (2.75–6)
Aerosol-generating procedureb	5 (14)
Unmasked during ED stayc	8 (23)
Positive SARS-CoV-2 PCR of accompanying guardian	10 (29)
Median lowest Ct value among E, RdRp, N gene from nasopharyngeal swab	26.01 (19.82–28.99)
Number of individuals with Ct value > 32	5 (14)
Total number of close contacts	58
Healthcare worker	16
Patient	26
Guardians	16
Median number of close contacts:	0 (0–2)
Healthcare worker	0 (0–0)
Patient	0 (0–1)
Guardians	0 (0–1)
Total number of casual contacts:	283
Healthcare worker	83
Patient	112
Guardians	88
Median number of casual contacts:	3 (0–10)
Healthcare worker	1 (0–2)
Patient	1 (0–5)
Guardians	0 (0–4)

Data are presented as the number (%) of patients or median with interquartile range (IQR). ED, emergency department; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; PCR, polymerase chain reaction.

^aWaves in Korea are defined as follows: the first wave was from 18th February to 5th May 2020, the second wave was from 12th August to 12th November 2020, and the third wave was from 13th November 2020 to now (https://www.mohw.go.kr/react/al/sal0301vw.jsp?PAR_MENU_ID=04&MENU_ID=0403&page=1&CONT_SEQ=362807).

^bAerosol-generating procedure was defined as open suctioning of airways, sputum induction, cardiopulmonary resuscitation, endotracheal intubation/extubation, non-invasive ventilation (e.g. bilevel positive airway pressure (BiPAP), continuous positive airway pressure (CPAP)), bronchoscopy, manual ventilation, nebulizer administration, and high-flow O₂ delivery (https://www.cdc.gov/coronavirus/2019-ncov/hcp/faq.html).

^cThey were unmasked due to high-flow O₂ therapy or non-compliance for masking.

Among the total of 341 contacts, only one patient (0.29%, 95%CI 0.05–1.64%) showed a positive polymerase chain reaction (PCR) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 2 days after contact with the index patient. The index patient (patient A) presented to the ED with a 1-day history of fever, nausea, and vomiting on February 2021 (third wave). The PCR test results obtained from a nasopharyngeal swab were positive (Ct value for E gene 10.64 cycles). Of the 13 contacts, one patient (patient B, initially classified as a casual contact) tested positive by PCR performed 2 days after contact because of fever (Supplementary Material). Patient B had entered the changing room 4 seconds after the index patient (patient A) had left, entered the negative-pressure room for PCR testing 13 minutes after the index patient had left, and finally stayed with the index patient in open beds located 2 meters apart for a total of 4 hours in zone 3 (Supplementary Material Fig. S1). Patients A and B stated that they had worn masks in the changing room. The changing room was not well ventilated and was a closed space. The air change rate in the negative-pressure room in which the PCR tests were performed was 25 per hour. To clarify the transmission route, we performed WGS of stored viral samples from these two cases (patients A and B) as well as another epidemiologically unrelated case (patient C). The viral genomes from patients A and B were 100% identical, while that from patient C showed a 12-nucleotide difference from those from patients A and B. All three genomes grouped phylogenetically with clade GH.

During the study period, we observed one transmission case from an infected patient with low Ct value to a patient in an ED that had implemented universal masking for patients and guardians and universal PPE for HCWs. Our previous study revealed the low risk of SARS-CoV-2 transmission in an outpatient clinic setting [2]. As expected, the transmission risk in the ED was relatively low but not negligible. However, there is a possibility of misclassification of contacts, and the transmission rate may be underestimated, especially in discharged patients and guardians. Our experience provides insight into the necessity for more isolation facilities and rapid test strategies, which may reduce the exposure time in the ED with limited isolation rooms.

As patient A had a low Ct value, the risk of transmission may be high [3]. The WGS result supported the transmission from patient A (index) to B. We later found that the changing room had no ventilation system or window, with a high risk of transmission. Infection control practitioners should thoroughly examine enclosed spaces and ventilation systems in the hospital.

In conclusion, one COVID-19 transmission case among a total of 341 contacts in the ED confirmed the preventative effects of PPE for HCWs and surgical masks for patients. However, prolonged stays in multiple open beds or using closed spaces may be risk factors for transmission.

Research ethics

This study was approved by the Institutional Review Board of our hospital, which waived the requirement for patient consent (2021-0545).

Author contributions

HC and JJ drafted the manuscript. MSP gave technical support. MNK and WYK critically reviewed the manuscript. JJ, SHK, and MSP contributed to conception and design. All authors read and approved the final version.

Transparency declaration

The authors declare no potential conflicts of interest. No financial support was received for this study.

Editor: L. Leibovici

Appendix A. Supplementary data

The following is the Supplementary data to this article: