The scientific data available confirm, on the whole, that transmission of SARS-CoV-2 can occur from aerosols containing particles that have retained their infectivity. However, we are unable today to determine the respective contributions of different SARS-CoV-2 transmission routes in the general population, i.e.:
- direct contact with an infected individual;
- transmission from droplets and aerosols over short distances (less than 2 metres);
- transmission from aerosols at a longer range;
- indirect contact via contaminated surfaces.
The respective contributions of these four transmission routes should to be quantified by the scientific community. In closed environments, this would be useful for example to adjust the management and social distancing measures required in different situations with differing parameters with regard to relative humidity, temperature and room volume, number of people present, whether there is a ventilation system or not, etc.
Acquiring new data to advance knowledge on the viability of the virus in the air
ANSES has identified the following research priorities:
- determine the viability of SARS-CoV-2 in the air under a variety of conditions representative of various indoor environments and of how much virus is actually shed by infected individuals, looking at viral load, the shedding matrix and environmental conditions, such as temperature, relative humidity and dust levels;
- acquire, share and pool data on possible clusters identified in public indoor spaces where conditions increase the risk of aerosol transmission, such as in restaurants, bars and sports facilities, and provide supporting contextual data on location, dates, volume of indoor space, ventilation, number of contaminated people, etc.;
- develop an understanding of the viral load in exhaled air as a function of disease history, infectivity and viral load distribution versus airborne droplet size.