❦ ‘There is robust evidence supporting the airborne transmission of many respiratory viruses, including measles virus, influenza virus, respiratory syncytial virus (RSV), human rhinovirus (hRV), adenovirus, enterovirus, severe acute respiratory syndrome coronavirus (SARS[-CoV-1]), Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2.

A growing body of research on COVID-19 provides abundant evidence for the predominance of airborne transmission of SARS-CoV-2.

This route dominates under certain environmental conditions, particularly indoor environments that are poorly ventilated, an observation that implicates solely aerosols because only aerosols – and not large droplets or surfaces – are affected by ventilation.

Additional precautionary measures must be implemented for mitigating aerosol transmission at both short and long ranges, with a major focus on ventilation, airflows, air filtration, UV disinfection, and mask fit.

Transmission of SARS-CoV-2 has occurred in healthcare settings despite medical [blue surgical/FRSM] masks (designed for droplets not aerosols) and eye protection, which illustrates the need for proper personal protective equipment (PPE) and layering multiple interventions against airborne transmission, especially in high-risk indoor settings.

Implementing effective ventilation systems reduces airborne transmission of infectious virus-laden aerosols. Strategies such as ensuring sufficient ventilation rates and avoiding recirculation are advised.

Carbon dioxide sensors can be used as indicators of the build-up of exhaled air and serve as a simple way to monitor and optimize ventilation.

Aerosol sensors can also be used to assess HEPA and HVAC aerosol filtration efficiencies, which are key to lowering infections caused by virus-laden aerosols.

Assuring a minimum ventilation rate of 4 to 6 air changes per hour (ACH) and maintaining carbon dioxide levels below 700 to 800 ppm have been advised, although the ventilation type and airflow direction and pattern should also be taken into account.

Increasing the efficiency of air filtration in HVAC systems, stand-alone HEPA purifiers, or implementing upper room UV disinfection systems can further reduce the concentrations of virus-laden aerosols.

These interventions are critical strategies for helping end the current pandemic and preventing future outbreaks.

The risk of outdoor transmission may rise with increased lifetime and transmissibility of viruses, such as certain variants of SARS-CoV-2.

Aerosolization of virus-containing wastewater and hospital fecal discharges also poses potential outdoor exposure risks, which should not be underestimated.’

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📖 (27 Aug 2021 ~ Science) Airborne transmission of respiratory viruses ➤

© 2021 Science.

📖 (13 Jan 2021 ~ Journal of Hospital Infection) Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) ➤

Illustration of short-range and long-range aerosol transmission of infectious SARS-CoV-2 particles.

[Original graphic adapted by C19.Life]