COVID-19 transmission: Up in the air
Lancet Respiratory Medicine, 29 Oct 2020
 Surface transmission is unlikely to be a major route of transmission, as although SARS-CoV-2 can persist for days on inanimate surfaces, attempts to culture the virus from these surfaces were unsuccessful.
 For social distancing to be effective, infective respiratory particles would need to fall to the ground or be in low enough concentrations at 2 m from the source to not cause transmission.
(WHO says 1 meter / CDC and NHS say 2 meters)
 Earlier threshold was 5 μm to differentiate between large and small particles, but 100 μm theshold could better differentiate the particles.
 Particles that would fall to the ground within 2 m are likely to be 60–100 μm in size.
 Pathogens are most commonly found in small particle aerosols (<5 μm), which are airborne and breathable.
 Transmission from people > 2 m apart has occurred but in enclosed spaces with poor ventilation, and typically with extended exposure to an infected person of more than 30 min.
 CDC says most infections are spread through close contact and that airborne transmission is not the primary route of transmission.
Link: Lancet Respiratory Medicine, 29 Oct 2020