Probable Aerosol Transmission of SARS-CoV-2 through Floors and Walls of Quarantine Hotel, Taiwan, 2021

Abstract

We investigated a cluster of SARS-CoV-2 infections in a quarantine hotel in Taiwan in December 2021. The cluster involved 3 case patients who lived in nonadjacent rooms on different floors. They had no direct contact during their stay. By direct exploration of the space above the room ceilings, we found residual tunnels, wall defects, and truncated pipes between their rooms. We conducted a simplified tracer-gas experiment to assess the interconnection between rooms. Aerosol transmission through structural defects in floors and walls in this poorly ventilated hotel was the most likely route of virus transmission. This event demonstrates the high transmissibility of Omicron variants, even across rooms and floors, through structural defects. Our findings emphasize the importance of ventilation and integrity of building structure in quarantine facilities.

Keywords: COVID-19; SARS-CoV-2; Taiwan; aerosol transmission; coronavirus disease; quarantine hotel; respiratory infections; severe acute respiratory syndrome coronavirus 2; vaccine-preventable diseases; viruses.

Figure 1

Timeline for Case A, Case B, and Case C in our investigation of aerosol transmission of the SARS-CoV-2 Omicron variant between separate, nonadjacent rooms in a quarantine hotel in Taipei City, Taiwan. Blue arrows indicate the results of the first RT-PCR testing, and red arrows indicate the results of the follow-up RT-PCR testing. The field investigation began on December 31, 2021.

Figure 2

Whole-genome sequencing of SARS-CoV-2 from 3 case patients (indicated with red triangles) who contracted COVID-19 in a quarantine hotel in Taipei City, Taiwan, in December 2021 (GISAID with accession ID EPI_ISL_13535670, 13535983, 13536113). Phylogenetic trees were constructed using IQ-TREE software (http://www.iqtree.org/) by maximum likelihood. The phylogenetic analysis with sequences obtained from the United States (1988 viruses), Japan (79 viruses, blue lines), and China (1 virus, red line) sampled from the same timeframe revealed that sequences of the 3 case patients fell into a subclade close to one from the United States. Scale bar for enlarged tree section indicates substitutions per site.

Figure 3

Simulation of probable air flow (arrows), implicating how virus-laden aerosol transported from the room of the primary case to the rooms of secondary cases in a quarantine hotel in Taipei City, Taiwan, December 2021. The bubbles symbol indicates the location of the source of transmission.