Alberta Health Services: COVID-19 Scientific Advisory Group Rapid Evidence Report, June 5, 2020 Transmission from HVAC Systems • 5 and isolation rooms in relation to spread of infectious diseases via the airborne route. Many of the epidemiological studies did not include adequate airflow studies (Y. Li et al., 2007). Luongo et al. (2016) systematic review assessed epidemiologic studies published after 2000 and investigating the association of at least one HVAC-related parameter with an infectious disease-related outcome in buildings. The authors indicate that the data implies that HVAC system factors in buildings have a role in airborne pathogen transmission, but more robust, interventional studies are needed (Luongo et al., 2016). SARS-CoV-2 & HVAC Systems in Healthcare Settings Liu et al. (2020) investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the COVID-19 outbreak in February and March 2020 (Liu et al., 2020). They collected thirty-five aerosol samples of three different types (total suspended particles, size- segregated, and deposition aerosol) in Patient Areas (PAA) and Medical Staff Areas (MSA) of Renmin Hospital of Wuhan University (Renmin) and Wuchang Fangcang Field Hospital (Fangcang), and Public Areas (PUA) in Wuhan, China during the outbreak. The ICU, CCU and general patient rooms inside Renmin, patient hall inside Fangcang had undetectable or low airborne SARS-CoV-2 concentration but deposition samples inside ICU and air sample in Fangcang patient mobile toilet room tested positive. The toilet room was a temporary single toilet room of approximately 1m2 in area without ventilation and had the highest viral load detected (19 copies/m2). The airborne SARS-CoV-2 in Fangcang MSA had bimodal distribution with higher concentrations than those in Renmin during the outbreak but were negative after number of patients were reduced and rigorous sanitization was implemented. Public areas had undetectable airborne SARS-CoV-2 concentration but obviously increased with accumulating crowd flow. The authors interpreted this to suggest overall low risks in the well ventilated or open public venues. The authors also concluded that room ventilation, open space, proper use and disinfection of toilets can effectively limit aerosol transmission of SARS-CoV-2. For example, the negative pressure ventilation and high air exchange rate inside ICU, CCU and ward room of Renmin Hospital were effective in minimizing airborne SARS-CoV-2. The authors further concluded that transmission within crowds via airborne transmission is possible. The virus aerosol deposition on protective apparel or floor surface and their subsequent resuspension is a potential transmission pathway and effective sanitization is critical in minimizing aerosol transmission of SARS- CoV-2 (Liu et al., 2020). Ong et al. (2020) collected surface environmental samples at 26 sites from three airborne infection isolation rooms (12 air exchanges per hour) with anterooms and bathrooms in the dedicated SARS-CoV-2 outbreak center in Singapore between January 24 and February 4, 2020. Note: viral culture was not done to demonstrate viability. There was extensive environmental contamination by one SARS-CoV-2 patient with mild upper respiratory tract involvement. Toilet bowl and sink samples were positive, suggesting that viral shedding in stool5 could be a potential route of transmission. Post-cleaning samples were negative, suggesting that current decontamination measures are sufficient. Air samples were negative despite the extent of environmental contamination. Two of the three swabs taken from the air exhaust outlets tested positive, suggesting that small virus-laden droplets may be displaced by airflows and deposited on equipment such as vents. The authors conclude the environment is a potential medium of transmission and supports the need for strict adherence to environmental and hand hygiene. Guo et al. (2020) tested surface and air (including air outlets) samples for SARS-CoV-2 using real-time PCR from an ICU and a general COVID-19 ward at Huoshenshan Hospital in Wuhan, China (Guo et al., 2020). Thirty-five percent (14/40) of the samples collected from the ICU and 12.5% (2/16) of the general ward samples were positive. Air outlet swab samples also yielded positive test results, with positive rates of 66.7% (8/12) of ICUs and 8.3% (1/12) for general wards. Rates of positivity differed by air sampling site with 44.4% (8/18) samples in patients’ rooms, 35.7% (5/14) near air outlets and 12.5% (1/8) in the doctors’ office area. The authors indicate that virus-laden aerosols were mainly concentrated near and downstream from the patients, with a maximum transmission distance of 4m. The air sampling sites in the general ward were distributed in different regions around the patient, under the air inlet, and in the patient corridor. Only air samples around the patient were positive. One of their conclusions was that SARS-CoV-2 was widely distributed in the air and on surfaces but did not associate this with HVAC systems (Guo et al., 2020). Both this and the Liu et al. (2020) study noted above are limited by the lack of viable virus testing. It is unclear whether environmental contamination with viral RNA contributes to clinical infection. 11.206
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