Leak-Testing of an Endoscopic Aerosol Box for Preventing SARS-CoV-2 Infection during Upper Gastrointestinal Endoscopy

Objective: The SARS-CoV-2 virus has infected many healthcare professionals. Endoscopy is an aerosol-generating procedure and the endoscopy team is at risk of exposure and infection. We describe the leak-testing of an aerosol box that uses a glove-covering for the endoscope.Materials and Methods: An endoscopic aerosol box with a glove-covering over the endoscope was made for gastroscopy, EUS and ERCP procedures and was tested for leakage of aerosol/airborne particles. Fine particulate matter (PM) from burnt incense sticks was used as a model for viral aerosol. The leakage from the box was measured by comparing readings from 2 PM light-scattering sensors, one placed inside the box and the other just outside the glove opening in a sealed container. Negative pressure conditions were also used to see if this had any effect on the leakage.Results: The concentration levels of the particulate matter differed with different negative pressure conditions and movement of the endoscope through the glove. Very little leakage was seen with the endoscope stationary even with no negative pressure, at 2.4%, 0.17% and 0.07% for PM1, PM2.5 and PM10, respectively. The maximum leakage was 14% for PM1, 8.7% for PM2.5 and 2.6% for PM10 in the moving-endoscope condition and no negative pressure. This reduced to 6.2%, 1.3%and 0.37% respectively when suction was applied at full strength (negative pressure of -0.05 bar). Conclusion: The glove covering significantly reduced the passage of particles. The particulate leak was seen most with the smallest particles and reached 14% for PM1 without negative pressure. This reduced to 6.2% with maximum negative pressure using the wall suction.

Why Does the SARS-CoV-2 Delta VOC Spread So Rapidly? Universal Conditions for the Rapid Spread of Respiratory Viruses, Minimum Viral Loads for Viral Aerosol Generation, Effects of Vaccination on Viral Aerosol Generation, and Viral Aerosol Clouds

This study analyzes the reasons the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant of concern (VOC) spreads so rapidly. Novel topics such as universal conditions for the rapid spread of respiratory viruses, minimum viral loads for viral aerosol generation, effects of vaccination on viral aerosol generation, and viral aerosol clouds were studied. The analyses were based on experimental results and analytic model studies. Four universal conditions, namely asymptomatic host, high viral load, stability of viruses in air, and binding affinity of viruses to human cells, need to be satisfied for the rapid spread of respiratory viruses. SARS-CoV-2 and its variants such as the Alpha VOC and Delta VOC satisfy the four fundamental conditions. In addition, there is an original principle of aerosol generation of respiratory viruses. Assuming that the aerosol–droplet cutoff particle diameter for distinguishing potential aerosols from earthbound respiratory particles is 100 μm, the minimum viral load required in respiratory fluids to generate viral aerosols is ~106 copies mL−1, which is within the range of the reported viral loads in the Alpha VOC cases and the Delta VOC cases. The daily average viral loads of the Delta VOC in hosts have been reported to be between ~109 copies mL−1 and ~1010 copies mL−1 during the four days after symptom onset in 1848 cases of the Delta VOC infection. Owing to the high viral load, the SARS-CoV-2 Delta VOC has the potential to effectively spread through aerosols. COVID-19 vaccination can decrease aerosol transmission of the SARS-CoV-2 Alpha VOC by reducing the viral load. The viral load can explain the conundrum of viral aerosol spreading. The SARS-CoV-2 Delta VOC aerosol clouds have been assumed to be formed in restricted environments, resulting in a massive numbers of infected people in a very short period with a high spreading speed. Strong control methods against bioaerosols should be considered in this SARS-CoV-2 Delta VOC pandemic. Large-scale environmental monitoring campaigns of SARS-CoV-2 Delta VOC aerosols in public places in many countries are necessary, and these activities could contribute to controlling the coronavirus disease pandemic.

Aerosol Transmission of Coronavirus and Influenza Virus of Animal Origin

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused great harm to global public health, resulting in a large number of infections among the population. However, the epidemiology of coronavirus has not been fully understood, especially the mechanism of aerosol transmission. Many respiratory viruses can spread via contact and droplet transmission, but increasing epidemiological data have shown that viral aerosol is an essential transmission route of coronavirus and influenza virus due to its ability to spread rapidly and high infectiousness. Aerosols have the characteristics of small particle size, long-time suspension and long-distance transmission, and easy access to the deep respiratory tract, leading to a high infection risk and posing a great threat to public health. In this review, the characteristics of viral aerosol generation, transmission, and infection as well as the current advances in the aerosol transmission of zoonotic coronavirus and influenza virus are summarized. The aim of the review is to strengthen the understanding of viral aerosol transmission and provide a scientific basis for the prevention and control of these diseases.

Why simple face masks are unexpectedly efficient in reducing viral aerosol transmissions

SummaryDuring the current pandemic and in the past, shortages of high quality respirators have forced people to protect themselves with homemade face masks that filter poorly in comparison to N95 respirators 1–4 and are often designed in ways that makes them susceptible to leaks 5,6. Nevertheless, there is compelling epidemiological 7,8 and laboratory evidence 9–12 that face masks can be effective in impeding the spread of respiratory viruses such as influenza and SARS-CoV-2. Here we show that this apparent inconsistency can be resolved with a simple face mask model that combines our filtration efficiency measurements of various mask materials with existing data on exhaled aerosol characteristics. By reanalyzing these data we are able to reconcile the vastly different aerosol size distributions reported 13–19 and derive representative volume distributions for speech and breath aerosol. Multiplying filtration efficiency by those aerosol volumes, which are proportional to emitted viral load, shows that electrostatically charged materials perform the best but that even most uncharged fabrics remove > 85 % of breath and > 99 % of speech aerosol volume for exhaled particles < 10 µm in diameter. A leak model we develop shows the best uncharged fabric masks are made of highly air-permeable and often thin materials reducing viral load by up to 45 % and 50 % for breath and speech, respectively. Less permeable materials provide reduced protection because unfiltered air is forced through the leak. This can even render some charged materials inferior to uncharged household materials. Our model also shows that thin fabric masks provide protection for the wearer from aerosols expelled by another person reducing inhaled viral load by up to 20 % and 50 % and if leaks are avoided up to 35 % and 90 % for breath and speech, respectively.