ABSTRACT
Difficulty in controlling SARS-CoV-2 transmission made the ability to inactivate viruses in aerosols and fomites to be an important and attractive risk reduction measure. Evidence that light frequencies have the ability to inhibit microorganisms has already been reported by many studies which, however, focused on ultraviolet (UV) wavelengths, which are known to induce potential injury in humans. In the present study, the effect on suspensions of SARS-CoV-2 of a Light Emitting Diode (LED) device capable of radiating frequencies in the non-hazardous visible light spectrum (VIS) was investigated. In order to evaluate the efficiency of viral inactivation, plaque assay and western blot of viral proteins were performed. The observed results showed a significant reduction in infectious particles that had been exposed to the LED irradiation of visible light. Furthermore, the analysis of the intracellular expression of viral proteins confirmed the inactivating effect of this irradiation technology. This in vitro study revealed for the first time the inactivation of SARS-CoV-2 through LED irradiation with multiple wavelengths of the visible spectrum. However additional and more in-depth studies can aim to demonstrate the data obtained during these experiments in different matrices, in mutable environmental conditions and on other respiratory viruses such as the influenza virus. The type of LED technology can decisively contribute on reducing virus transmission through the continuous sanitation of common environments without risks for humans and animals.
ABSTRACT
This study aimed at the identification of the settings linked to SARS-CoV-2 transmission through the analysis of clusters and small outbreaks detected by the Lombardy Region surveillance system during the second epidemic wave. Comparing the data before and after the introduction of restrictive measures (night curfew, partial closure of schools and businesses, smaart working), we observed a significant decrease of infections in workplaces, social gatherings, coffee shops, restaurants, and sports centers; contagion in schools decreased from 9.2% to 3.4%, in hospitals environments and nursing homes from 5% to 2%; domestic infections increased instead from 73.5% to 92.7%. These results suggest that containment measures have been effective in controlling virus circulation in the community but not at the household level and might inform future interventions, including the establishment of structures (Covid Hotels) for the isolation infected people. At the same time, they raise awareness on the risk of transmission among family members and during households social gatherings.