Detection of Air and Surface Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Hospital Rooms of Infected Patients

Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies. We aimed to detect SARS-CoV-2 surface and air contamination and study associated patient-level factors. 245 surface samples were collected from 30 airborne infection isolation rooms of COVID-19 patients, and air sampling was conducted in 3 rooms. Air sampling detected SARS-CoV-2 PCR-positive particles of sizes >4 μm and 1-4 μm in two rooms, which warrants further study of the airborne transmission potential of SARS-CoV-2. 56.7% of rooms had at least one environmental surface contaminated. High touch surface contamination was shown in ten (66.7%) out of 15 patients in the first week of illness, and three (20%) beyond the first week of illness (p = 0.01).

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The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi. org/10.1101org/10. /2020 In the room of Patient 1, three NIOSH samplers were attached to each of two tripod stands 1 0 7 and situated at different heights from the ground (1.2m, 0.9m, and 0.7m) near the air exhaust 1 0 8 to capture particles from the unidirectional airflow in the room. Throughout the four-hour 1 0 9 sampling period, Patient 1 was intermittently facing the NIOSH samplers while seated one 1 1 0 meter from the first tripod and 2.1 meters from the second tripod. Four SKC 37mm PTFE 1 1 1 filter (0.3μm pore size) cassettes were also distributed throughout the room and connected to 1 1 2 SKC Universal air sampling pumps set at a flow-rate of 5 L/min, each collecting an  In the rooms of Patients 2 and 3, three NIOSH samplers were attached to each of two tripod 1 1 5 stands and situated at different heights from the ground (1.2m, 0.9m, and 0.7m). Throughout  The 6 NIOSH samples from each room were pooled prior to analysis, but the particle size 1 2 1 fractions remained separated. Each sample pool was representative of 5,040 L air. general ward rooms (Supplemental Figure 1). In ICU rooms, the ventilator and infusion (Supplemental Figure 2). Air exhaust outlets and glass window surfaces were sampled in five 1 3 0 All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10. 1101/2020 rooms, including the three rooms in which air sampling was performed. Toilet seat and 1 3 1 automatic flush button (one combined swab) were sampled in AIIR rooms in the general All samples were immediately stored at 4°C in the hospital prior to transfer to a BSL-3 1 3 5 laboratory where samples were immediately processed and stored at -80°C unless directly analyzed. Prior to RNA extraction, NIOSH aerosol sample tubes and filters were processed as 1 3 7 previously described (7), with slight modification due to the pooling of samples. The QIAamp viral RNA mini kit (Qiagen Hilden, Germany) was used for sample RNA 1 4 0 extraction. Real-time PCR assays targeting the envelope (E) genes (8) and an in house orf1ab 1 4 1 assay were used to detect SARS-CoV-2 in the samples (9). All samples were run in duplicate 1 4 2 and with both assays. Positive detection was recorded as long as amplification was observed  We analyzed the factors associated with environmental contamination using the Student t- depending on their distribution. The χ 2 or Fisher exact test was used to compare categorical 1 5 3 All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10. 1101/2020 variables. We plotted the best fit curve by least-square method to study the environmental 1 5 4 contamination distribution across various the days of illness and clinical Ct value. symptoms, and three patients (10%) had fever or myalgia only (Supplemental Table 1).

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There were no baseline differences between patients with environmental surface  (Table 1).

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Of the rooms with environmental contamination, the floor was most likely to be contaminated 1 6 8 (65%), followed by the bed rail (59%), and bedside locker (42%) (Figure 1). Contamination sampling. We did not detect surface contamination in any of the three ICU rooms.  (Table 1). In a subgroup analysis, the presence and extent of high-touch surface 1 7 6 contamination were significantly higher in rooms of patients in their first week of illness 1 7 7 All rights reserved. No reuse allowed without permission.
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The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10. 1101/2020 ( Figure 2). The best fit curve with the least-squares fit (Figure 3) showed that the extent of 1 7 8 high-touch surface contamination declined with increasing duration of illness and Ct values. Air samples from two (66.7%) of three AIIRs tested positive for SARS-CoV-2, in particle 1 8 2 sizes >4 µm and 1-4 µm in diameter (Table 1). Total SARS-CoV-2 concentrations in air 1 8 3 ranged from 1.84x10 3 to 3.38x10 3 RNA copies per m 3 air sampled. Rooms with viral 1 8 4 particles detected in the air also had surface contamination detected.   Additionally, a recent laboratory study demonstrated the ability of SARS-CoV-2 to remain 1 9 7 viable in aerosols for up to 3 hours (11). While limited in subject numbers, our study 1 9 8 examined this issue at the individual patient-level, thus enabling correlation of particle size author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi. org/10.1101org/10. /2020 of our current findings being iatrogenic in nature. Larger individual patient-level studies   Our study was limited in that it did not determine the ability of SARS-CoV-2 to be cultured and efforts to design a culture method to isolate virus from our samples is underway. Second, 2 2 0 sampling in an AIIR environment may not be representative of community settings and 2 2 1 further work is needed to generalize our current findings. Third, we sampled each room at a 2 2 2 single timepoint during the course of illness and did not track environmental contamination hours of environmental testing, it is plausible that during the day of testing, viral load was 2 2 5 actually low or negligible, hence limiting environmental contamination.

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All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https: //doi.org/10.1101//doi.org/10. /2020 Current epidemiologic evidence does not seem to point to aerosolization as the key route of 2 2 7 transmission of SARS-CoV-2 (16). Detailed epidemiologic studies of outbreaks, in both 2 2 8 healthcare and non-healthcare settings, should be carried out to determine the relative 2 2 9 contribution of various routes of transmission and their correlation with patient-level factors. In conclusion, in a limited number of AIIR environments, our current study involving  author/funder, who has granted medRxiv a license to display the preprint in perpetuity. for their roles in the study. team and clinical diagnostics team for BSL3 sample processing and analysis as well as the 2 5 0 logistics and repository team for transport of biohazard material, inventory and safekeeping 2 5 1 of received items. None reported. 19 Research Fund (COVID19RF-001) and internal funds from DSO National Laboratories.

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Ng OT is supported by NMRC Clinician Scientist Award (MOH-000276). K Marimuthu is  author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10. 1101/2020 The funders had no role in the design and conduct of the study; collection, management, 2 6 5 analysis and interpretation of the data; preparation, review or approval of the manuscript; and 2 6 6 decision to submit the manuscript for publication.

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All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10. 1101/2020