Two concentration peaks in sub- and supermicron ranges are present in aerosols, implying that they do not necessarily appear together, indicating possible different formation mechanisms.
-	The submicron aerosol may come from the resuspension of virus-laden aerosol from medical staff protective equipment due to its greater degree of mobility
-	The supermicron virus-laden aerosol may come from the resuspension of dust particles from floors or other hard surfaces


University of California, Davis

To understand the aerosol transmission route of SARS-CoV-2, this study aimed to:
-	Quantify the concentrations of airborne SARS-CoV-2 both inside hospitals and in outdoor areas where public gatherings are common
-	Evaluate the aerodynamic size distributions of SARS-CoV-2 aerosols that may facilitate its airborne transmission in different settings
-	Determine the dry deposition rate of the airborne SARS-CoV-2 in an ICU patient ward room

It concluded that:
- Room ventilation, open space, and proper disinfection of toilets can limit aerosol transmission of virus particles
- Crowds with asymptomatic carriers is a potential source of airborne SARS-CoV-2
- The virus aerosol deposition on PPE or floor surfaces and subsequent resuspension is a potential transmission pathway
- Rigorous sanitization protocols are critical in slowing the spread of the virions

Study on Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosols in Wuhan, China

Liu, Y., Ning, Z., Chen, Y., Guo, M., Liu, Y., Gali, N. K., ... & Liu, X. (2020). Aerodynamic characteristics and RNA concentration of SARS-CoV-2 aerosol in Wuhan hospitals during COVID-19 outbreak. BioRxiv.

https://doi.org/10.1101/2020.03.08.982637

Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosol in Wuhan Hospitals during COVID-19 Outbreak

TSP - Total Suspended Particles

Sampling was done between February 17th and March 2nd, 2020 in two different hospitals of Wuhan and various public areas.

Table 1: Sample Collection of Aerosolized SARS-CoV-1 in Wuhan, China

For Remnin Hospital:
-	Negative results of airborne SARS-CoV-2 RNA concentration may be owed to the negative pressure ventilation and high air exchange rate inside the ICU, CCU, and ward rooms
-	The MSAs had low concentrations, this is thought to be sourced from the resuspension of floor dust aerosol containing SARS-CoV-2 transferred from the PAAs

For Fangcang Field Hospital:
-	The PARRs have a higher concentration, this may be sourced from the resuspension of the aerosolized virus particles from the surface of medical staff protective equipment while they are removed
-	The second batch of TSP samples taken in Fangang MSAs all tested negative following the reduction of patient numbers and implementation of more thorough sanitation measures
-	The highest concentration in PAAs was in the mobile toilet room

For PUAs:
-	Asymptomatic carriers of COVID-19 may contribute as a source of virus-laden aerosol

Airborne SARS-CoV-2 concentrations
 (TSP samples)

Size distribution of SARS-CoV-2 aerosol (Size Segregated Samples)

Longer sampling time of 7 days for the deposition samples compared to the 3 hour period for TSP samples contribute to the accumulation of virus sediment. Aerosol deposition may be a major part in surface contamination leading to subsequent infection by contact with susceptible people. Aerosols may deposit on the surface of medical staff PPEs and the floors in patient areas and are then resuspended in the air by the movements of medical staff and equipment.

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