Abstract
COVID-19 disease is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which originated in Wuhan, China and spread with an astonishing rate across the world. The transmission routes of SARS-CoV-2 are still debated, but recent evidence strongly suggests that COVID-19 could be transmitted via air in poorly ventilated places. Some studies also suggest the higher surface stability of SARS-CoV-2 as compared to SARS-CoV-1. It is also possible that small viral particles may enter into indoor environments from the various emission sources aided by environmental factors such as relative humidity, wind speed, temperature, thus representing a type of an aerosol transmission. Here, we explore the role of relative humidity in airborne transmission of SARS-CoV-2 virus in indoor environments based on recent studies around the world. Humidity affects both the evaporation kinematics and particle growth. In dry indoor places i.e., less humidity (< 40% RH), the chances of airborne transmission of SARS-CoV-2 are higher than that of humid places (i.e., > 90% RH). Based on earlier studies, a relative humidity of 40–60% was found to be optimal for human health in indoor places. Thus, it is extremely important to set a minimum relative humidity standard for indoor environments such as hospitals, offices and public transports for minimization of airborne spread of SARS-CoV-2.
Highlights
The World Health Organization (WHO) declared a global pandemic for the outbreak of novel coronavirus disease, which is a highly transmittable and pathogenic viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Sanders et al, 2020; WHO, 2020b)
The overall geographic range of COVID-19 spread is much larger as compared with the epidemic of the severe acute respiratory syndrome (SARS) in 2003 (WHO, 2004)
We have found that there are three different scenarios where RH affects virus transmission in the indoor surroundings (a) fate of microorganisms inside the viral droplets (b) survival or inactivation of virus on surfaces (c) role of dry indoor air in airborne transmission of viruses
Summary
The World Health Organization (WHO) declared a global pandemic for the outbreak of novel coronavirus disease (nCOVID-19), which is a highly transmittable and pathogenic viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Sanders et al, 2020; WHO, 2020b). We have found that there are three different scenarios where RH affects virus transmission in the indoor surroundings (a) fate of microorganisms inside the viral droplets (b) survival or inactivation of virus on surfaces (c) role of dry indoor air in airborne transmission of viruses. Based on the Lin and Marr (2020) findings, the viability is typically much lower at a RH around 60% (~55%) This is because evaporation kinetics plays an important role in modulating the survival of the microorganism within the droplets or aerosols. Lower temperatures and low humidity support prolonged survival of virus on contaminated surfaces Another important point to mention here is that, the virus transmission has often occurred in well air-conditioned environments such as hospitals or hotels in some countries which has intensive use of air-conditioning (Chan et al, 2011)
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