key: cord-1022065-teolr1e9 authors: Ang, Alicia XY; Luhung, Irvan; Ahidjo, Bintou A.; Drautz‐Moses, Daniela I.; Tambyah, Paul A.; Mok, Chee Keng; Lau, Kenny JX; Tham, Sai Meng; Chu, Justin Jang Hann; Allen, David M.; Schuster, Stephan C. title: Airborne SARS‐CoV‐2 surveillance in hospital environment using high‐flowrate air samplers and its comparison to surface sampling date: 2021-09-14 journal: Indoor Air DOI: 10.1111/ina.12930 sha: e4138420a357e7f3d091b6c7fec0890012eda6fa doc_id: 1022065 cord_uid: teolr1e9 Reliable methods to detect the presence of SARS‐CoV‐2 at venues where people gather are essential for epidemiological surveillance to guide public policy. Communal screening of air in a highly crowded space has the potential to provide early warning on the presence and potential transmission of SARS‐CoV‐2 as suggested by studies early in the epidemic. As hospitals and public facilities apply varying degrees of restrictions and regulations, it is important to provide multiple methodological options to enable environmental SARS‐CoV‐2 surveillance under different conditions. This study assessed the feasibility of using high‐flowrate air samplers combined with RNA extraction kit designed for environmental sample to perform airborne SARS‐CoV‐2 surveillance in hospital setting, tested by RT‐qPCR. The success rate of the air samples in detecting SARS‐CoV‐2 was then compared with surface swab samples collected in the same proximity. Additionally, positive RT‐qPCR samples underwent viral culture to assess the viability of the sampled SARS‐CoV‐2. The study was performed in inpatient ward environments of a quaternary care university teaching hospital in Singapore housing active COVID‐19 patients within the period of February to May 2020. Two types of wards were tested, naturally ventilated open‐cohort ward and mechanically ventilated isolation ward. Distances between the site of air sampling and the patient cluster in the investigated wards were also recorded. No successful detection of airborne SARS‐CoV‐2 was recorded when 50 L/min air samplers were used. Upon increasing the sampling flowrate to 150 L/min, our results showed a high success rate in detecting the presence of SARS‐CoV‐2 from the air samples (72%) compared to the surface swab samples (9.6%). The positive detection rate of the air samples along with the corresponding viral load could be associated with the distance between sampling site and patient. The furthest distance from patient with PCR‐positive air samples was 5.5 m. The airborne SARS‐CoV‐2 detection was comparable between the two types of wards with 60%–87.5% success rate. High prevalence of the virus was found in toilet areas, both on surfaces and in air. Finally, no successful culture attempt was recorded from the environmental air or surface samples. Countries, regions, and cities have individually and collectively gone under varying degrees of physical distancing in a bid to control the spread of the COVID-19 pandemic. International travel has been significantly reduced, and numerous social and educational activities have been severely restricted. These measures have had an extraordinary impact on a global scale. A robust surveillance method for the presence of SARS-CoV-2 in the environment is essential to allow safe resumption of normal activities, given that it could require multiple years to achieve reasonable vaccination rate globally. 1 There is also no assurance that vaccines will eliminate the need for continued physical distancing. 2 A large-scale and accurate test regime that could detect the virus will aid in designing practical screening strategies. Currently, SARS-CoV-2 testing is performed on an individual level, which has proven to be laborious and costly. 3 To overcome these limitations, community testing using air, surface, and sewage samples are being explored. In practice, wastewater testing is currently the most ad- analysis, as approved for nasopharyngeal testing. [5] [6] [7] [8] [9] [10] Further, successful environmental surveillance through air is especially relevant as infection via SARS-CoV-2 containing aerosols is increasingly being considered as alternative route of transmission. 11 While the definition of "aerosol" varies across different practitioners, 12 there has been growing evidence that supports airborne transmission route of the virus. [13] [14] [15] Though limited in number, some studies on airborne SARS-CoV-2 have demonstrated success in culturing the virus from aerosol samples. 16, 17 Recently, human challenge studies have also been approved in the UK that seek to test airborne transmission in healthy human individuals. 18 To contribute to the existing efforts of assessing the potential of air sampling as a tool to detect the presence of SARS-CoV-2 in the environment, we undertook air and surface sampling in naturally ventilated open-cohort ward and mechanically ventilated isolation ward within a large hospital. As regulations and restrictions between hospitals and other facilities where COVID-19 patients, either symptomatic or asymptomatic, may congregate differ worldwide, it is important to provide multiple methodological options to enable environmental SARS-CoV-2 surveillance in a variety of settings. The aims of this study are threefold. First, this study assesses the feasibility of deploying high-flowrate air sampler in combination with environmental sample RNA extraction kit for the purpose of SARS-CoV-2 surveillance in hospital setting. Second, this study aims to investigate the spatial prevalence of the virus in various areas of the hospital when it was fully utilized to care for COVID-19 patients (ie, in toilets, in different wards, at hallways or at a certain distance from the patient clusters). Finally, the success rate of the tested air surveillance approach is compared to the surface swab sampling and analysis pipeline, which has been more established in our hospital. The two surveillance approaches were tested for direct detection of SARS-CoV-2 in the environment and in terms of their potential to conduct culture-based assessment. Air and surface samples were collected from one isolation ward and two open-cohort wards housing laboratory-confirmed COVID-19 patients at the National University Hospital, an academic medical center, in Singapore. The isolation ward, defined as ward 62 in this study, consists of negative pressure single rooms, each with a dedicated toilet, as previously described. 19 It is equipped with a the virus was found in toilet areas, both on surfaces and in air. Finally, no successful culture attempt was recorded from the environmental air or surface samples. communal testing, COVID-19, environmental surveillance, high-flowrate air sampling • Deploying high-flowrate air samplers was found to improve the success rate of airborne SARS-CoV-2 detection. • An opposing association was observed between airborne SARS-CoV-2 detection and the distance of air sampling site to the patients. • Our air surveillance approach produced a higher success rate of environmental SARS-CoV-2 detection than the surface sampling. • Both air and surface sampling highlighted the high prevalence of the virus in toilet areas of the hospital wards • None of the RT-qPCR-positive air or surface samples was successfully cultured. mechanical ventilation with a design Air Change per Hour (ACH) of 14. The room temperature (T) and relative humidity (RH) were strictly maintained at 23°C and 60%, respectively, during operation. The two open-cohort wards, defined as ward 42 and ward 43, are located on the same floor and have similar indoor settings. At the beginning of the pandemic in Singapore, the wards were re-purposed to exclusively care for COVID-19 patients. The wards were segregated into staff areas, designated as "clean" zones, and patient care areas, designated as "contaminated" zones. The contaminated zones consisted of five open cubicles, each housing six patients, and two smaller rooms, each housing one patient. Each room or cubicle has a dedicated toilet, and these rooms and cubicles share a common corridor. The main difference between the two wards is the distance between the designated clean and contaminated zones. As ward 42 had a slightly smaller total ward area, the distance between the The study was conducted within the period of February to May 2020. This period was within the peak of the first wave of COVID-19 cases in Singapore. Due to the large number of cases, all three wards were fully occupied by COVID-19 patients at the time of sampling (confirmed by nasopharyngeal swab (N/P) test). We were unable to obtain the exact Ct values of the N/P test for the involved patients due to logistic issues and data access restrictions from a number of clinical laboratories across Singapore. All patients involved during the study, however, could be considered as mildly symptomatic without significant hypoxia or need for oxygen, as such patients would have been admitted to the intensive care ward instead. All patients were masked with regular surgical mask whenever possible. There was no distinction between the patients housed in ward 62, 42, or 43 as they were admitted to the next available slot as they arrive in the hospital. All air sampling was conducted with filter-based SASS 3100 air samplers (Research International). The sampler collects total suspended particle (TSP) with no particle size cutoff. The filter media were the default 44 mm diameter SASS bioaerosol filter (polyester material, no electrostatic charge, Research International) with two different pore-sizes. As per the manufacturer's specification, the small poresize filter has an efficiency of 90% for particles <0.5 µm with 50 L/ min sampling flowrate, whereas the large pore-size filter has an efficiency of 50% for particles <0.5 µm with 150 L/min sampling flowrate. The air sampler, along with the selected filter media, has been well studied for their use in sampling and analyzing environmental biological 20-22 and chemical aerosols. 23 All air samples were duplicated for environmental SARS-CoV-2 test and for culturing (only for positive samples). Three sampling campaigns were conducted in ward 62 (isolation ward). For the first sampling campaign, three sets of air samplers were placed in the toilet, windowsill (closed), and cardiac table next to the patient. This arrangement corresponds to 0.9-3 m of distance to the patient (details in Table 1 ). The three sets of samplers were running simultaneously using the small pore-size filter (90% efficiency, 50 L/min flowrate) This sampling arrangement covered a range of 2.5 m to 13 m distance between sampling sites and patients (details in Table 1 ). The second campaign only interrogated ward 42 as ward 43 was not available for sampling. Three sets of samplers with large pore-size filters were placed in donning area (clean zone), patient care area and toilet (contaminated zone). In total, three air samples were The presence of SARS-CoV-2 was detected by RT-qPCR of the E- the estimated LOD of the sample will be 3.1 copies/cm 2 of surface. Culture was performed using African green monkey kidney cells As the study was conducted at the early stage of the pandemic, The first air sampling campaign of the study was conducted in the Interestingly, we also found that the differences in Ct values were higher in the air samples (3-5 Ct differences, Table 1 ) as compared to surface swab samples (1-2 Ct differences, Table 2 ). The E-gene is the envelope protein gene, whereas the N-gene is the nucleocapsid protein gene. A future study involving a more controlled laboratorybased experiment is necessary to pinpoint the exact cause. However, we suspect that these are caused by differences in assay efficiencies. It is also possible that it is an artifact of the two sampling approaches and the subsequent processing pipelines. Drawing conclusions from quantitative comparison of multiple studies must In summary, our findings continue to support the suitability of using The authors declare no conflict of interests. The peer review history for this article is available at https://publo ns.com/publo n/10.1111/ina.12930. The data that support the findings of this study are available from the corresponding author upon reasonable request. Alicia XY Ang https://orcid.org/0000-0002-6949-6994 David M. Allen https://orcid.org/0000-0001-5333-1258 Stephan C. 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