Ventilation and detection of airborne SARS-CoV-2: elucidating high-risk spaces in naturally ventilated healthcare settings (preprint)

Background: In healthcare settings in low- and middle-income countries, which frequently rely upon natural ventilation, the risk of aerosol transmission of SARS-CoV-2 remains poorly understood. We aimed to 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. Methods: We measured outdoor and room CO2 to estimate absolute ventilation (liters per second [L/s]) from 9 hospitals in Bangladesh during October 2020 - February 2021. We estimated infectious risk across different spaces using a modified Wells-Riley equation. We collected air samples from these same spaces at 12.5 L/min over 30 minutes and performed RT-qPCR to detect SARS-CoV-2 N-gene. We used multivariable linear regression and calculated elasticity to identify characteristics associated with ventilation. Results: Based on ventilation of 86 patient care areas and COVID-19 case numbers, we found that over a 40-hour exposure period, outpatient departments posed the highest median risk for infection (5.4%), followed by COVID intensive care units (1.8%). We detected SARS-CoV-2 RNA in 18.6% (16/86) of air samples. Ceiling height and total open area of doors and windows were found to have the greatest impact on ventilation. Conclusion: Our 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.

Physical integrity of medical exam gloves with repeated applications of disinfecting agents: evidence for extended use (preprint)

Background: The COVID-19 pandemic has created global shortages of personal protective equipment (PPE) such as medical exam gloves, forcing healthcare workers to either forgo or reuse PPE to keep themselves and patients safe from infection. In severely resource-constrained situations, limited cycles of disinfection and extended use of gloves is recommended by the U.S. Centers for Disease Control and Prevention (CDC) to conserve supplies. However, these guidelines are based on limited evidence. Methods: Serial cycles of hand hygiene were performed on gloved hands using alcohol-based hand rub (ABHR) (six and ten cycles), 0.1% sodium hypochlorite (bleach) solution (ten cycles), or soap and water (ten cycles) on three types of latex and three types of nitrile medical exam gloves, purchased in the United States and India. A modified FDA-approved water-leak test was performed to evaluate glove integrity after repeated applications of these disinfecting agents. 80 gloves per disinfectant-glove type combination were tested. Within each glove type the proportion of gloves that failed the water-leak test for each disinfectant was compared to that of the control using a non-inferiority design with a non-inferiority margin of five percentage points. Results were also aggregated by glove material, and combined for overall results. Findings: When aggregated by glove material, the dilute bleach exposure demonstrated the lowest difference in proportion failed between treatment and control arms: -2.5 percentage points (95% CI: -5.3 to 0.3) for nitrile, 0.6 percentage points (95% CI: -2.6 to 3.8) for non-powdered latex. For US-purchased gloves tested with six and ten applications of ABHR, the mean difference in failure risk between treatment and control gloves was within the prespecified non-inferiority margin of five percentage points or less, though some findings were inconclusive because confidence intervals extended beyond the non-inferiority margin. The aggregated difference in failure risk between treatment and control gloves was 3.5 percentage points (0.6 to 6.4) for soap and water, and 2.3 percentage points (-0.5 to 5.0) and 5.0 percentage points (1.8 to 8.2) for 10 and 6 applications of ABHR, respectively. The majority of leaks occurred in the interdigital webs (35%) and on the fingers (34%). Conclusion: Current guidelines do not recommend extended use of a single-use PPE under normal supply conditions. However, our findings indicate that some combinations of glove types and disinfection methods may allow for extended use under crisis conditions. We found that ten applications of dilute bleach solution have the least impact on glove integrity, compared to repeated applications of ABHR and soap and water. However, the majority of glove and exposure combinations were inconclusive with respect to non-inferiority with a 5 percentage point non-inferiority margin. Testing specific glove and disinfectant combinations may be worthwhile for settings facing glove shortages during which extended use is necessary. The modified water-leak testing method used here is a low-resource method that could easily be reproduced in different contexts.