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. 2020 Jul 23;222(4):564-571.
doi: 10.1093/infdis/jiaa334.

Airborne SARS-CoV-2 Is Rapidly Inactivated by Simulated Sunlight

Michael Schuit  1 , Shanna Ratnesar-Shumate  1 , Jason Yolitz  1 , Gregory Williams  1 , Wade Weaver  1 , Brian Green  1 , David Miller  1 , Melissa Krause  1 , Katie Beck  1 , Stewart Wood  1 , Brian Holland  1 , Jordan Bohannon  1 , Denise Freeburger  1 , Idris Hooper  1 , Jennifer Biryukov  1 , Louis A Altamura  1 , Victoria Wahl  1 , Michael Hevey  1 , Paul Dabisch  1
Affiliations

Airborne SARS-CoV-2 Is Rapidly Inactivated by Simulated Sunlight

Michael Schuit et al. J Infect Dis. .

Abstract

Aerosols represent a potential transmission route of COVID-19. This study examined effect of simulated sunlight, relative humidity, and suspension matrix on stability of SARS-CoV-2 in aerosols. Simulated sunlight and matrix significantly affected decay rate of the virus. Relative humidity alone did not affect the decay rate; however, minor interactions between relative humidity and other factors were observed. Mean decay rates (± SD) in simulated saliva, under simulated sunlight levels representative of late winter/early fall and summer were 0.121 ± 0.017 min-1 (90% loss, 19 minutes) and 0.306 ± 0.097 min-1 (90% loss, 8 minutes), respectively. Mean decay rate without simulated sunlight across all relative humidity levels was 0.008 ± 0.011 min-1 (90% loss, 286 minutes). These results suggest that the potential for aerosol transmission of SARS-CoV-2 may be dependent on environmental conditions, particularly sunlight. These data may be useful to inform mitigation strategies to minimize the potential for aerosol transmission.

Keywords: COVID-19; SARS-CoV-2; aerosol decay; aerosol persistence; relative humidity; sunlight.

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Figures

Figure 1.
Figure 1.
Representative spectra for simulated sunlight. Simulated sunlight spectra utilized in the present study (black lines), spectra from the National Center for Atmospheric Research (NCAR) tropospheric ultraviolet and visible (TUV) radiation model for noon at 40°N latitude at sea level (gray lines), and spectra measured for darkness (blue lines) are shown (for color figure refer online version). A, Spectra for high-intensity simulated sunlight and TUV model for 21 June. B, Spectra for midintensity simulated sunlight and TUV model for both 7 March and 4 October. C, Spectra for high-intensity simulated sunlight and TUV model for 21 June, with irradiance plotted logarithmically. D, Spectra for midintensity simulated sunlight and TUV model for both 7 March and 4 October, with irradiance plotted logarithmically. Integrated irradiances for the UVA and UVB portions of the spectra for both the measured and TUV model spectra demonstrate close agreement between the measured and model values. For high-intensity simulated sunlight, measured integrated UVB irradiance was 1.91 W/m2 vs 1.84 W/m2 predicted by TUV for 21 June. Measured integrated UVA irradiance was 69.76 W/m2 vs 58.50 W/m2 predicted by TUV for 21 June. For midintensity simulated sunlight, measured integrated UVB irradiance was 0.94 W/m2 vs 0.92 W/m2 predicted by TUV for 7 March and 4 October. Measured integrated UVA irradiance was 31.97 W/m2 vs 40.54 and 40.25 W/m2 predicted by TUV for 7 March and 4 October, respectively. No irradiance was detectable above the background of the spectroradiometer measured in darkness for wavelengths less than approximately 295 nm. Vertical dashed lines represent the cutoffs between UVC and UVB (280 nm), and UVB and UVA (315 nm).
Figure 2.
Figure 2.
Aerosol decay data for SARS-CoV-2 at 20°C. Tests were conducted in darkness (A), at midintensity simulated (Sim.) sunlight (B), and at high-intensity simulated sunlight (C). Data from tests with the virus suspended in simulated saliva and culture medium are shown in white and grey, respectively, with bars indicating the arithmetic mean ± standard deviation of the kInfectivity values for each data set. kInfectivity was dependent on the simulated sunlight intensity and the suspension matrix (P < .0001 and P = .0004, respectively), but not relative humidity (RH).
Figure 3.
Figure 3.
Representative viral and mass aerosol concentration profiles for SARS-CoV-2 in simulated saliva. Representative decay profiles and associated decay constants for both viral infectivity and aerosol mass from individual tests are shown for (A) no simulated sunlight at 20% relative humidity and 20°C, (B) midintensity simulated sunlight at 45% relative humidity and 20°C, and (C) high-intensity simulated sunlight at 70% relative humidity and 20°C. The decay of the aerosol mass concentration, in log10 mg/m3 (black circles), was similar across the 3 tests, while the decay rate of infectious viral aerosols, in log10 median tissue culture infectious dose/L (TCID50/L) air (white circles), increased as the intensity of simulated sunlight was increased. The dashed line at 0.97 log TCID50/Lair indicates the limit of detection for infectious virus; points on this line were not included in curve fits.
See this image and copyright information in PMC

Comment in

  • Simulated Sunlight Rapidly Inactivates SARS-CoV-2 on Surfaces.
    Ratnesar-Shumate S, Williams G, Green B, Krause M, Holland B, Wood S, Bohannon J, Boydston J, Freeburger D, Hooper I, Beck K, Yeager J, Altamura LA, Biryukov J, Yolitz J, Schuit M, Wahl V, Hevey M, Dabisch P. Ratnesar-Shumate S, et al. J Infect Dis. 2020 Jun 29;222(2):214-222. doi: 10.1093/infdis/jiaa274. J Infect Dis. 2020. PMID: 32432672 Free PMC article.

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