Assessing impact of ventilation on airborne transmission of SARS-CoV-2: a cross-sectional analysis of naturally ventilated healthcare settings in Bangladesh

Abstract

ObjectivesTo evaluate the risk of exposure to SARS-CoV-2 in naturally ventilated hospital settings by measuring parameters of ventilation and comparing these findings with results of bioaerosol sampling.Study designCross-sectional study.Study setting and study sampleThe study sample included nine hospitals in Dhaka, Bangladesh. Ventilation characteristics and air samples were collected from 86 healthcare spaces during October 2020 to February 2021.Primary outcomeRisk of cumulative SARS-CoV-2 infection by type of healthcare area.Secondary outcomesVentilation rates by healthcare space; risk of airborne detection of SARS-CoV-2 across healthcare spaces; impact of room characteristics on absolute ventilation; SARS-CoV-2 detection by naturally ventilated versus mechanically ventilated spaces.ResultsThe majority (78.7%) of naturally ventilated patient care rooms had ventilation rates that fell short of the recommended ventilation rate of 60 L/s/p. Using a modified Wells-Riley equation and local COVID-19 case numbers, we found that over a 40-hour exposure period, outpatient departments posed the highest median risk for infection (7.7%). SARS-CoV-2 RNA was most frequently detected in air samples from non-COVID wards (50.0%) followed by outpatient departments (42.9%). Naturally ventilated spaces (22.6%) had higher rates of SARS-CoV-2 detection compared with mechanically ventilated spaces (8.3%), though the difference was not statistically significant (p=0.128). In multivariable linear regression with calculated elasticity, open door area and cross-ventilation were found to have a significant impact on ventilation.ConclusionOur findings provide evidence that naturally ventilated healthcare settings may pose a high risk for exposure to SARS-CoV-2, particularly among non-COVID-designated spaces, but improving parameters of ventilation can mitigate this risk.

Investigation on the effectiveness of ventilation dilution on mitigating COVID-19 patients’ secondary airway damage due to exposure to disinfectants

“…Compared with the IAQ parameters measured in the ICU wards of permanent hospitals worldwide [ 8 , 23 , 31 , [36] , [37] , [38] , [39] , [40] , [41] ], the temperature was lower, the RH was higher, and the CO 2 and the PM 2.5 concentrations were similar in the two ICU wards of LSS Hospital ( Fig. 7 , Fig.…”

“…ICU, intensive care unit; ASHRAE, American Society of Heating, Refrigerating and Air-Conditioning Engineers; AIIR, airborne infection isolation room . Except for this study, the temperature and relative humidity (RH) data points depicted were collected from ICU wards admitting coronavirus disease 2019 (COVID-19) patients in permanent hospitals worldwide ( Table S6 ) [ 8 , 23 , 31 , [36] , [37] , [38] , [39] , [40] , [41] ].The average temperature and RH in these permanent ICU wards were 25.1 °C and 38.1%, represented by the blue dash–dot line and the pink dash–double dot line, respectively. Most of the included studies presented the temperature and RH data as the mean ± standard deviation and thus, our results are also presented in this format.…”

“…Our data are presented as boxplots, with the whiskers representing minimum and maximum values, the box representing the range from the lower to upper quartiles, and the square symbol and the line in the box representing the mean and median values, respectively. Except for this study, the CO 2 and PM 2.5 concentration data were collected from ICU wards admitting coronavirus disease 2019 (COVID-19) patients in permanent hospitals worldwide ( Table S6 ) [ 23 , 31 , [36] , [37] , [38] , 40 , 41 ]. The average CO 2 and PM 2.5 concentrations in these permanent ICU wards were 579 ppm (ppm = 10 −6 mol/mol) and 21 μg/m 3 , represented by blue and red dashed lines, respectively.…”

“…Some studies have measured IAQ parameters, including temperature, RH, carbon dioxide (CO 2 ) and fine particulate matter (PM 2.5 ) concentrations while air sampling in ICU wards that admit COVID-19 patients [ 8 , 23 , 31 , [36] , [37] , [38] , [39] , [40] , [41] ] and have also reported the ventilation rates of these ICUs [ 8 , 23 , 31 , 40 ].These studies have helped us to gain knowledge of the IAQ to which severely ill COVID-19 patients are exposed in ICU wards. However, these studies have mainly focused on exploring the possibility of airborne transmission of SARS-CoV-2, rather than elucidating the IAQ, or discussing by-products from the widespread use of disinfectants during COVID-19 pandemic.…”

Genetic Load of SARS-CoV-2 in Aerosols Collected in Operating Theaters

“…Therefore, inhalation of virus laden aerosols, especially indoors ( 2 , 3 ), and contact with contaminated surfaces are the main routes of transmission ( 4 , 5 ). In fact, genetic traces of SARS-CoV-2 have been detected in air filters collected in hospital environments ( 6 – 10 ) and not only in spaces with COVID-19 patients ( 7 , 11 ). In fact, higher levels of SARS-CoV-2 genetic material have been detected in hospital corridors than in rooms of infected patients, which has been attributed to the ventilation systems ( 12 ).…”