Solar UV–B/A Radiation is Highly Effective in Inactivating SARS-CoV-2

Abstract

It is well known that 200-290 nm ultraviolet photons (hereinafter UV-C radiation) photo-chemically interacts with DNA and RNA and are endowed with germicidal properties that are also effective on viruses. Fortunately, Solar UV-C photons of this wavelength are filtered out by the Ozone layer of the upper Atmosphere, at around 35 km. Softer UV photons from the Sun with wavelengths in the range 290-320 nm (UV-B) and 320-400 nm (UV-A), however, do reach the Earth s surface. The effect of these photons on Single- and Double-Stranded RNA/DNA viruses and the possible role they play on the seasonality of epidemics, are nevertheless little studied and highly debated in alternative or complementarity to other environmental causes. Notably though, the effects of both direct and indirect radiation from the Sun needs to be considered in order to completely explain the effects of UV radiations in life processes (with e.g. the UV virucidal effect enhanced in combination to the concomitant process of water droplets depletion because of Solar heat). Herein we present a number of concurring circumstantial evidence suggesting that the evolution and strength of the recent Severe Acute Respiratory Syndrome (SARS-Cov-2) pandemics, might be have been modulated by the intensity of UV-B and UV-A Solar radiation hitting different regions of Earth during the diffusion of the outbreak between January and May 2020. Out findings, if confirmed by more in depth data analysis and modeling of the epidemics, which includes Solar modulation, could help in designing the social behaviors to be adopted depending on season and environmental conditions.

Forcing Seasonality of influenza-like epidemics with daily Solar resonance

“…The efficiency of the solar-pump is here parameterized through the parameter ε (in the interval [0,1]) but depends, effectively, on internal virus properties, namely the lethal time τ 0 needed to deliver the UV lethal dose D 0 (defined as the UV-C fluence needed to inactivate 63% of the virus) for the given virus (Nicastro et al, 2020, submitted). At local noon (the minima of the daily solar curves of Fig.…”

“…Lytle and Sagripanti, 2005; Lubin and Jense, 1995) and the possible role they play on the seasonality of epidemics e.g Martinez, 2018), are nevertheless little studied. In two companion papers, we present a number of concurring circumstantial pieces of evidence suggesting that the evolution and strength of the recent Severe Acute Respiratory Syndrome (SARS-Cov-2) pandemics (Zhu et al, 2019; Cobey, 2020), might have been modulated by the intensity of UV-B and UV-A Solar radiation hitting different regions of Earth during the diffusion of the outbreak between January and July 2020 (Nicastro et al, 2020, submitted), and provide a measurement of the lethal UV-C dose for Covid-19 (Bianco et al, 2020, submitted).…”

“…Prather et al, 2020 and references therein). Additionally, the time needed for aerosol particles to gravitationally settle has to be comparable or longer than the typical UV-B/A virus’s lethal time (Nicastro et al, 2020, submitted). This is probably not true (in still air) for the largest (~100 μm in size) and thus heaviest droplets produced in coughs and sneezes, where the gravitational settling time is of the order of few seconds (Morawska and Cao, 2020), but can certainly be the case for significantly smaller, micron or sub-micron size, aerosol particles (like those that commonly contain the influenza virus, e.g.…”

Associations of Acute Exposure to Airborne Pollutants with COVID-19 Infection: Evidence from China

“…Pawar also indicates that although a strong relationship between recovered cases and death cases was observed, changes in temperature showed no signi cant correlation with con rmed cases in China by linear regression models (Pawar et al 2020). In addition, ultraviolet photons has also been considered to play the possible role in the modulation of COVID-19 epidemiology (Nicastro et al 2020).…”

On the anti-correlation between COVID-19 infection rate and natural UV light in the UK

“…Another study [3] pointed out that UV radiation will not be effective in places with high air pollution, where UV light turns into heat. On the other hand, other studies [4][5][6] have found that UV light is associated with decreased COVID-19 growth rate. Given the disagreement on the impact of UV light on COVID-19 transmission we take a fresh look at data for the UK.…”