SAVES US: Suppression of Airborne Viral Epidemic Spread by Ultraviolet light barriers

ABSTRACT

Despite the gradual return to pre-pandemic conditions, the spreading of COVID-19 (SARS-CoV-2) left several open issues. Nowadays it is know that airborne infections, including COVID-19, are conveyed by particles having the size of >5 μm (droplets) and <5 μm (droplets nuclei), ejected by coughing and sneezing [1]. While droplets undergo to dehydration and precipitation, droplet nuclei persist in air for long time after their ejection, contributing to infection spreading. Actual prevention strategies are based on non-pharmaceutical interventions act to reduce droplets diffusion and spacing from Personal Protective Equipment, such as facial masks, and social distancing measure. Nevertheless, for the new endemic phase of COVID-19 the development of new strategies for airborne infections' containment becomes unavoidable. In this project, we propose a new device for the suppression of Airborne Viral Aerosols designed to work in situations with constrained geometries (e.g. public transportation, offices, waiting rooms etc.) not allowing social distancing. The device, devised to perform photokilling of viral aerosols in air in presence of humans, has its core in an UV illumination system operating at 222 nm. It is know from literature that UV radiation alters the genetic material of viruses and bacteria whose maximum absorption wavelengths are in the far-UV range (UVC, 100-280 nm), the most effective for sterilization [2]. Differently from the operative wavelength of most commercial systems (254 nm), the higher tissue absorption prevents the 222 nm radiation to travel over the very first epidermal layers [3] constituting a minor health risk for applications in presence of people. The device combines the UV illumination system with a vertical flux of air that conveys exhaled particles to the light source and controls humidity and temperature, crucial parameters for virus diffusion. After its development, the device prototype will be tested in model experiments. Initially, its safety will be verified by monitoring in particular the UVC-induced ozone production. Then, in vitro photokilling experiments will be performed in two steps: (i) on a layer of immobilized SARS-Cov-2 virus act to obtain optimal UV doses for an effective sterilization;(ii) on SARS-Cov-2 aerosol models. For this last experiment, a model viral aerosol miming the characteristics of cough and sneeze particles will be preliminary studied and supported by synthetic data to characterize the optical properties of the reference scenario. The resulting information will be crucial for the final design of the device itself. As a last step, we will test the device in in vivo experiments. An air flux, harvesting exhaled air by infected mice, will be illuminated by the device and will be sent to healthy mice. Finally, the infectiveness of exhaled air after the UV treatment will be evaluated, providing more information for further applications in the presence of humans.