SARS-CoV-2, How to prevent indoor infection

SARS-CoV-2 indoor prevention

Maintaining the right degree of humidity and adequate air exchange prevents the spread of the virus in indoor environments, especially where the risk is higher, such as hospitals and medical practices. This is confirmed by an international study conducted, among others, by CNR-Isac researchers and published in the International Journal of Environmental Research and Public Health (https://www.mdpi.com/1660-4601/17/22/8553).

It is well known that Sars-Cov-2 is not only transmitted by direct contact, but it can spread through the air by "droplets", the droplets of nebulized saliva. "Although the virus itself is about a hundred nanometers in size (the diameter of a hair is 50,000-180,000 nanometers), it has been verified that an infected person, through breathing, vocalization, coughing, sneezing, can emit an aerosol potentially containing SARS-CoV-2," explains Francesca Costabile, researcher at the Institute of Atmospheric Sciences and Climate of the National Research Council (CNR-Isac).

A study published in the International Journal of Environmental Research and Public Health by Cnr-Isac, in collaboration with the German Leibniz Institute for Tropospheric Research, the CSIR- National Physical Laboratory of India and 2B Technologies- Boulder (USA), suggests appropriate strategies to prevent and mitigate the risk of airborne transmission of the virus. "In addition to their composition, the particles of these aerosols vary considerably in size, from less than 1,000 nanometers, the diameter of particulate matter, to values greater than 5,000 nanometers, the size of typical respiratory droplets," Costabile continues. "The relationship between inhaled dose and infectivity for SARS-CoV-2 strongly depends on the size: the ability to penetrate the lower respiratory tract, systemic translocation throughout the human body and attack on particularly vulnerable target organs, first of all the brain".

The risk, in short, varies drastically with the size of these aerosol particles. "Inspired by the precautionary principle, the main objective of the work was to recognize, based on already published data, the existence of a risk due to the possible airborne transmission of SARS-CoV-2 in particular indoor environments. And therefore propose simple and clear guidelines to hospitals, medical practices, public places and other similar environments", warns the researcher Cnr-Isac. "Robust laboratory results show that the virus transmission, in environments without solar radiation, is favoured by dry and cold conditions. On this basis - indoors with direct cold, dry, direct sunlight and insufficient ventilation - we recommend first of all: to maintain adequate humidification of the indoor air (in the range 40-60%), especially when temperatures are below 20°C, the use of air purifiers, adequate mechanical ventilation even in winter periods and the measurement of the concentration of carbon dioxide (CO2) in the air, to be maintained below 1000 ppm. Finally, we do not recommend the use of nebulizers in some medical procedures and types of disinfectants for cleaning such as hydrogen peroxide. In the absence of these precautions the risk could remain even if wearing the surgical mask".
These guidelines aim to reduce the risk of airborne transmission, for example in hospitals and nursing homes, as there are still few countries such as Canada, Belgium and Switzerland that have adopted strategies against the potential risk of airborne transmission of SARS-CoV-2, thanks to the support of scientists. "We believe that this is one of the most important tasks for research at this particular time," Dr. Costabile concludes. "Our study represents one of the results of the line of research outlined within the CNR-Isac with the creation of thematic working groups dedicated to Covid-19 in the lockdown period".

Interview: Rai UnoMattina Dec. 8, 2020 from min 23.57  https://www.raiplay.it/video/2020/11/Unomattina-ecdfe3b8-fa38-4c9c-9dd2-a912a95d2c78.html

Publication: Strategies for prevention and mitigation of airborne transmission risk of Sars-Cov-2 Ahlawat, A.; Mishra, S.K.; Birks, J.W.; Costabile, F.;Wiedensohler, A. Preventing Airborne Transmission of SARS-CoV-2 in Hospitals andNursing Homes. Int. J. Environ. Res. Public Health 2020, 17, 8553. https://www.mdpi.com/1660-4601/17/22/8553

Contacts: Francesca Costabile, Cnr-Isac, francesca.costabile [at] artov.cnr.it