Stability of SARS-CoV-2 in different environmental conditions, SARS-CoV-2 in wastewater, and guidance on repurposing anaesthesia machines as ventilators
By Denise Baez
NEW YORK -- April 3, 2020 -- Today’s DG Alert covers stability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in different environmental conditions, the potential risk of SARS-CoV-2 in wastewater, and repurposing anaesthesia machines as intensive care unit (ICU) ventilators.
According to a study published in The Lancet Microbe, SARS-CoV-2 can be highly stable in a favourable environment, but it is also susceptible to standard disinfection methods.
Alex W. H. Chin, MD, University of Hong Kong, Hong Kong, China, and colleagues conducted various experiments to test the stability of SARS-CoV-2 at different temperatures, on various surfaces, and its susceptibility to disinfection methods.
First, the researcher measured the stability of SARS-CoV-2 at different temperatures. SARS-CoV-2 in virus transport medium (final concentration ∼6.8 log unit of 50% tissue culture infectious dose [TCID50] per mL) was incubated for up to 14 days and then tested for its infectivity.
Results showed that SARS-CoV-2 is highly stable at 4 degrees Celsius, but sensitive to heat. At 4 degrees Celsius, there was only around a 0.7 log-unit reduction of infectious titre on day 14. When the incubation temperature increased to 70 degrees Celsius, the time for virus inactivation was reduced to 5 mins.
The researchers then investigated the stability of this virus on different surfaces, including paper, tissue paper, wood, cloth, glass, banknotes, stainless steel, plastic, and surgical masks. Briefly, a 5 μL droplet of virus culture (∼7.8 log unit of TCID50 per mL) was pipetted on a surface and left at room temperature (22 degrees Celsius) with a relative humidity of around 65%. The inoculated objects retrieved at desired time-points were immediately soaked with 200 μL of virus transport medium for 30 mins to elute the virus.
No infectious virus could be recovered from printing and tissue papers after a 3-hour incubation, whereas no infectious virus could be detected from treated wood and cloth on day 2. By contrast, SARS-CoV-2 was more stable on smooth surfaces. No infectious virus could be detected from treated smooth surfaces on day 4 (glass and banknote) or day 7 (stainless steel and plastic).
Strikingly, a detectable level of infectious virus was still present on the outer layer of a surgical mask on day 7 (∼0.1% of the original inoculum).
The researchers also tested the virucidal effects of disinfectants by adding 15 μL of SARS-CoV-2 culture (∼7.8 log unit of TCID50 per mL) to 135 μL of various disinfectants at working concentration. Disinfectants included household bleach, hand soap, ethanol, povidone-iodine, chlorhexidine, and benzalkonium chloride. With the exception of a 5-minute incubation with hand soap, no infectious virus could be detected after a 5-minute incubation at room temperature.
In another article, published in The Lancet Gastroenterology & Hepatology, researchers report the detection of SARS-CoV-2 in wastewater.
From February 17, 2020, onwards, Willemijn Lodder, and Ana Maria de Roda Husman, Centre for Infectious Disease Control, Bilthoven, the Netherlands, took samples once a week from human wastewater collected at Amsterdam Airport Schiphol, Haarlemmermeer, the Netherlands, for virus analyses. Samples tested positive for virus RNA by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) methodology 4 days after the first cases of coronavirus disease 2019 (COVID-19) were identified in the Netherlands on February 27, 2020.
“This could be explained by virus excretion from potentially symptomatic, asymptomatic, or pre-symptomatic individuals passing through the airport,” the authors wrote. “Furthermore, human wastewater sampled near the first Dutch cases in Tilburg, Netherlands, also tested positive for the presence of viral RNA within a week of the first day of disease onset. These findings indicate that wastewater could be a sensitive surveillance system and early warning tool, as was previously shown for poliovirus.”
“Whether SARS-CoV-2 is viable under environmental conditions that could facilitate faecal-oral transmission is not yet clear…[however], the possibility of faecal-oral transmission of COVID-19 has implications, especially in areas with poor sanitation where diagnostic capacity might be limited, such as Africa. Wastewater surveillance, especially in areas with a scarcity of data, might be informative, as we have previously shown in monitoring antibiotic resistance on a global scale.”
Lastly, the American Society of Anesthesiologists (ASA) have published guidance on how to safely and effectively convert anaesthesia into life-sustaining mechanical ventilation for patients during the COVID-19 pandemic, when there are not sufficient ICU ventilators to meet patient care needs.
Although guidance is available from the manufacturers, the guidance may not convey all of the clinical considerations. Anaesthesia professionals will be needed to put these machines into service and to manage them while in use. Safe and effective use requires an understanding of the capabilities of the machines available, the differences between anaesthesia machines and ICU ventilators, and how to set anaesthesia machine controls to mimic ICU-type ventilation strategies.
Detailed information is provided and a quick reference guide (PDF) is available for downloading. The quick reference guide is intended to be a bedside tool and includes a suggested schedule for monitoring the effectiveness and safety of the anaesthesia ventilator.
The ASA is working with component societies to develop an inventory of local resources with the goal of moving machines to the locations where they are most needed. Anaesthesia machines not currently being used may be located in hospital operating rooms, nearby ambulatory surgery centres, nearby office-based surgery practices, and through anaesthesia equipment distributors.
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