Transmission of Omicron (B.1.1.529) - SARS-CoV-2 Variant of Concern in a designated quarantine hotel for travelers: a challenge of elimination strategy of COVID-19

Abstract

With the global evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), for almost 2 years, various control strategies have been utilized around the world. While most of the western countries gradually lifted the border control and quarantine measures, elimination strategy aiming at “zero COVID-19” remains in place in Western Pacific Region such as mainland China and Hong Kong, where inbound travelers are required to undergo quarantine in designated quarantine hotels (DQHs) for up to 21 days. However, not designed for the purpose of quarantine, especially for infectious diseases with potential airborne spread, DQHs may be potential venues for COVID-19 transmission.1Dinoi A Feltracco M Chirizzi D Trabucco S Conte M Gregoris E et al.A review on measurements of SARS-CoV-2 genetic material in air in outdoor and indoor environments: Implication for airborne transmission.Sci Total Environ. 2021; 151137Crossref PubMed Scopus (1) Google Scholar We recently reported an incident of community outbreak of imported SARS-CoV-2 beta variant due to possible intra-hotel transmission in a DQH.2Cheng VC Siu GK Wong SC Au AK Ng CS Chen H et al.Complementation of contact tracing by mass testing for successful containment of beta COVID-19 variant (SARS-CoV-2 VOC B.1.351) epidemic in Hong Kong.Lancet Reg Health West Pac. 2021; 17100281Summary Full Text Full Text PDF PubMed Google Scholar Smoke tests in DQHs demonstrated that aerosols could leak out from guest rooms to the corridors, and guests in neighboring rooms may inhale the infectious aerosols when the doors were opened.3Wong SC Chen H Lung DC Ho PL Yuen KY Cheng VC. To prevent SARS-CoV-2 transmission in designated quarantine hotel for travelers: Is the ventilation system a concern?.Indoor Air. 2021; 31: 1295-1297Crossref PubMed Scopus (2) Google Scholar We also conducted a serological survey of the hotel staff members in the implicated DQHs, which showed no serological evidence of guest-to-staff-to-guest transmission of COVID-19.4Li X Chen H Lu L Chen LL Chan BP Wong SC et al.High compliance to infection control measures prevented guest-to-staff transmission in COVID-19 quarantine hotels.J Infect. 2021; (S0163-4453(21)00533-8)Summary Full Text Full Text PDF Google Scholar This provides reassurance that our infection control training of hotel staff members, which was similar to the training of healthcare workers in hospitals and community treatment facilities, was effective at preventing intra-hotel transmission to staff.5Wong SC Leung M Tong DW Lee LL Leung WL Chan FW et al.Infection control challenges in setting up community isolation and treatment facilities for patients with coronavirus disease 2019 (COVID-19): Implementation of directly observed environmental disinfection.Infect Control Hosp Epidemiol. 2021; 42: 1037-1045Crossref PubMed Scopus (6) Google Scholar After this incident, portable air purifiers with high-efficiency particulate air filters were installed in the corridors of DQHs. Residents are required to wear surgical mask for the purpose of mutual protection while opening the doors. Despite these additional measures, another incident of SARS-CoV-2 transmission inside a DQH was reported.6Gu H Krishnan P Ng DYM Chang LDJ Liu GYZ Cheng SSM et al.Probable Transmission of SARS-CoV-2 Omicron Variant in Quarantine Hotel, Hong Kong, China, November 2021.Emerg Infect Dis. 2021 Dec 3; 28https://doi.org/10.3201/eid2802.212422Crossref PubMed Google Scholar The asymptomatic index case (M/36), who had completed two doses of BNT162b2 mRNA COVID-19 vaccine (BioNTech) in June 2021, had anti-spike protein receptor-binding domain (anti-RBD) of 1142 AU/ml (14 November 2021). The secondary case (M/62) also completed two doses of BioNTech in May 2021. He developed respiratory symptoms on day 8 after arrival and clinically stable after hospitalization, with anti-RBD of 250 AU/ml (19 November 2021). Both cases had no chronic illness. Whole genome sequences of specimens collected from the two cases were different by only 1 nucleotide and belonged to the Omicron variant (B.1.1.529 lineage).6Gu H Krishnan P Ng DYM Chang LDJ Liu GYZ Cheng SSM et al.Probable Transmission of SARS-CoV-2 Omicron Variant in Quarantine Hotel, Hong Kong, China, November 2021.Emerg Infect Dis. 2021 Dec 3; 28https://doi.org/10.3201/eid2802.212422Crossref PubMed Google Scholar To understand the mechanism of transmission, we performed smoke test during our on-site investigation on 22 November 2021. Smoke test demonstrated stagnant air in the corridor (width: 1.5 m; height: 2 m) adjoining the two rooms (index case: room A; secondary case: room B), and there was brief outward movement of air when the doors of the guest rooms were opened abruptly. Therefore, the virus-laden aerosol may escape into the guest room of the secondary case when the door was opened, either slightly or widely (Figure 1a and 1b). In fact, the index case did not wear mask or just wore cloth mask when opening the door to fetch food or discard garbage bags upon our direct questioning. We also assess the extent of environmental contamination. Environmental swabs were taken from room B using methods described previously.7Cheng VC Wong SC Chan VW So SY Chen JH Yip CC et al.Air and environmental sampling for SARS-CoV-2 around hospitalized patients with coronavirus disease 2019 (COVID-19).Infect Control Hosp Epidemiol. 2020; 41: 1258-1265Crossref PubMed Scopus (79) Google Scholar One of 8 (12.5%) specimens collected from high-level non-reachable surfaces (wall or ceiling: 50 × 20 cm in size) on 22 November 2021 (3 days after transfer-out of the case) tested positive for SARS-CoV-2 by RT-PCR (cycle threshold value: 39). Partial spike gene sequence of this environmental swab had a nucleotide identity of 100% with those from the cases, suggestive of air dispersal of Omicron variant. Furthermore, 21 of 39 (53.8%) commonly touched surfaces were positive in room B, with positive rate 8 times higher than the contamination rate in quarantine rooms reported previously.8Liu J Liu J He Z Yang Z Yuan J Wu H et al.Duration of SARS-CoV-2 positive in quarantine room environments: A perspective analysis.Int J Infect Dis. 2021; 105: 68-74Summary Full Text Full Text PDF PubMed Scopus (6) Google Scholar SARS-CoV-2 B.1.1.529 was first identified in a specimen collected on 9 November 2021 and was reported to the World Health Organization on 24 November 2021. Its emergence was associated with a steep increase of COVID-19 infections in South Africa.9Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern. World Health Organization (published 26th November 2021). Available at https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern. Accessed on 27th November 2021.Google Scholar Potential air dispersal, extensive environmental contamination, and airborne transmission of Omicron variant have been demonstrated in this incident, which likely will pose a greater challenge to the “zero COVID” strategy in Hong Kong. Nosocomial transmission of COVID-19 can be prevented by the utilization of airborne infection isolation facilities in hospitals.10Wong SC Yuen LL Chan VW Chen JH To KK Yuen KY et al.Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): What is the implication of hospital infection control?.Infect Control Hosp Epidemiol. 2021 Jul 12; : 1-2https://doi.org/10.1017/ice.2021.318Crossref Scopus (2) Google Scholar For the DQHs. we may maximize the flow rate of air exhaust in guest rooms, further increase fresh air supply, and supplement with air purifiers in corridors, in addition to enhanced training of environment disinfection and use of personal protective equipment. Alternatively, quarantine camp with individual isolation unit and natural ventilation in the open area or more frequent testing may be considered for persons returning from high-risk areas with Omicron transmission. All authors declare no conflict of interest. We thank Electrical and Mechanical Services Department, Buildings Department, and Public Health Laboratory Services Branch of Centre for Health Protection, HKSAR Government to provide technical support in this investigation. We gratefully acknowledge the originating and submitting laboratories who contributed sequences to GISAID (Supplementary Table S1). S-CW and VC-CC had roles in study design, data analysis, and writing up of the manuscript. S-CW, AK-WA, CH, DCL, K-YY, and VC-CC had roles in outbreak investigation. KK-WT and DCL had roles in whole genome sequencing and phylogenetic analysis. LX, AW-HC, JDI, W-MC, and H-WT had roles in laboratory work. S-CW, AK-WA, and LL-HY had roles in collection of environmental and clinical specimens. All authors reviewed and approved the final version of the manuscript. This study was partially supported by the Health and Medical Research Fund (HMRF) Commissioned Research on Control of Infectious Disease (Phase IV), CID-HKU1-2 and CID-HKU1-16, Food and Health Bureau, and Theme-Based Research Scheme T11-709/21-N, Hong Kong SAR Government.

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