Value of a mask mandate: Goldman Sachs says One trillion dollars. Chicken feed these days. https://www.forbes.com/sites/sarahh...y-1-trillion-goldman-sachs-says/#701132f256f1 AIRBORNE TRANSMISSION While we continue to learn more about the SARS-CoV-2 virus, many uncertainties remain, particularly with respect to modes of transmission. As we previously covered, emerging evidence supports the possibility of airborne/aerosol transmission of the virus, and a number of health experts recently called on the WHO to update its transmission and infection control guidance to place greater emphasis on airborne transmission risk. The WHO did issue updated guidance on SARS-CoV-2 transmission, which noted the possibility of airborne transmission. However, the document continues to emphasize that droplet transmission is believed to be the principal driver of the pandemic. A recent study published (preprint) by researchers at several US health and academic institutions provides additional evidence supporting the possibility of airborne transmission. The researchers collected aerosol samples from 6 COVID-19 patient treatment areas to determine the presence of SARS-CoV-2 in the airborne environment. The specimens were analyzed to identify the presence of infectious virus in various particle sizes—greater than 4.1 µm, 1-4 µm, and less than 1 µm—via “real-time reverse-transcriptase polymerase chain reaction (rRT-PCR), cell culture, western blot, and transmission electron microscopy (TEM).” The study identified viral RNA in all 6 patient rooms and in all 3 particle sizes. Additionally, the researchers were able to culture viable virus from multiple aerosol samples in the “less than 1 µm” category. While this study demonstrates that viable virus can be present in aerosol form, additional research is necessary to determine the role it plays in transmission. In particular, questions remain regarding the infectious dose for SARS-CoV-2, especially with respect to the amount of virus present in aerosols, and how long the virus can remain viable in aerosol form.