A psychrometric model to assess the biological decay of the SARS-CoV-2 virus in aerosols

Abstract

There is increasing evidence that the 2020 COVID-19 pandemic has been influenced by variations in air temperature and humidity. However, the impact that these environmental parameters have on survival of the SARS-CoV-2 virus has not been fully characterised. Therefore, an analytical study was undertaken using published data to develop a psychrometric model to assess the biological decay rate of the virus in aerosols. This revealed that it is possible to describe with reasonable accuracy (R2 = 0.718, p < 0.001) the biological decay constant for the SARS-CoV-2 virus using a regression model with enthalpy, vapour pressure and specific volume as predictors. Applying this to historical meteorological data from London, Paris and Milan over the pandemic period, produced results which indicate that the average half-life of the virus in aerosols outdoors was in the region 13–22 times longer in March 2020, when the outbreak was accelerating, than it was in August 2020 when epidemic in Europe was at its nadir. However, indoors, this variation is likely to be much less. As such, this suggests that changes in virus survivability due the variations in the psychrometric qualities of the air might influence the transmission of SARS-CoV-2.

End-to-end SARS-CoV-2 transmission risks in sport: Current evidence and practical recommendations

“…A study of environmental SARS-CoV-2 in the rooms of quarantining confirmed positive cases found 29/55 surfaces in the rooms of symptomatic cases were positive for SARS-CoV-2 by RT-qPCR; however, no viable virus was isolated in cell culture. [38] As such, the contribution of fomites to the transmission of SARS-CoV-2 is controversial, [39] and remains relatively unknown, [25] in part due to no minimum infectious dose of SARS-CoV-2 being established, [40] hampering studies of transmission dynamics from surfaces.…”

“…[127] Further considerations should also be made when the air is cooler and drier, given that it has been shown that the SARS-CoV-2 virus survives in aerosols for considerably longer, [27,28,128] and the viral half-life is >10 times longer during the winter and autumn months compared with the summer. [25] Breaks and social interactions Similar to many other occupational settings, individuals in sport may have coffee and lunch breaks throughout the day. These breaks can become high SARS-CoV-2 transmission risk situations, due to multiple people congregating in one location (e.g.…”

“…opening windows and doors). [24,25] It has been shown that the SARS-CoV-2 virus survives in aerosols for longer when the air is cooler and drier. [21,26] The viral half-life is >10 times longer outdoors during the winter and autumn months compared with the summer.…”

“…[21,26] The viral half-life is >10 times longer outdoors during the winter and autumn months compared with the summer. [25] Even though a room space may be heated in winter, the air can still be very dry (e.g. 10-40% relative humidity).…”

“…The viral load in any droplets inhaled may be substantially greater than would be the case during the summer months. [25] While the implications of this are not yet fully understood, it may explain in part the seasonal variation in COVID-19 case numbers that have been observed in many temperate regions. UVB radiation in sunlight has also been shown to rapidly degrade the virus.…”