UV-C and COVID-19

Researchers in Italy have found that it is possible to completely inactivate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using short-wavelength UV (UV-C) irradiation.

At a viral concentration equivalent to the low-level found in settings such as hospital rooms and to the level typically found in the sputum of coronavirus disease 2019 (COVID-19) patients, a very low dose of UV-C radiation was sufficient to inactivate SARS-CoV-2 completely.

At a viral input equivalent to that found in terminally ill patients, a higher dose of radiation also completely inactivated the virus.

The results also have extremely important implications for the design and development of effective sterilization methods for containing SARS-CoV-2, they add.

Disinfection technologies are urgently needed

Since its outbreak in Wuhan, China, in December last year, the COVID-19 pandemic has had a devastating impact on people’s health globally and the world’s economic outlook.

Clerici and colleagues say the identification of “microbicide” methods that will minimize any future spread of SARS-CoV-2 is essential since the virus can survive outside of the body in the air for hours.

In this context, non-contact disinfection technologies are highly desirable, and UV radiation, in particular UVC (200 – 280 nm), is one of the most reliable and widely accepted approaches.

According to the authors, many studies have explored how UV-C radiation destroys viruses, and the most common mechanism is “direct absorption of the UV-C photon by the nucleic acid basis or capsid proteins leading to the generation of photoproducts that inactivate the virus.”

What did the study involve?

Using a low-pressure mercury lamp system, the team administered different UV-C doses (3.7, 16.9 and 84.4 mJ/cm2) to SARS-CoV-2 at a multiplicity of infection (MOI) of 0.05 (equivalent to low-level contamination); 5 (equivalent to the level in sputum from COVID-19 patients) and 1000 (equivalent to the level in cases of terminal disease).

At low and intermediate contamination levels, a very small dose of UV-C inactivated the virus.

At the lowest MOI (0.05), viral replication was wholly inhibited after six days, even at the low UV-C dose of 3.7 mJ/cm2.

At the intermediate contamination level (MOI of 5), viral replication was effectively reduced by this low dose after 24 hours and did not increase over time, indicating a complete inactivation of the virus. Evaluation of cytopathic effects also confirmed virus inactivation.

A higher dose was required for the highest contamination level.

At the highest viral input (MOI of 1000), viral replication significantly decreased in a dose-dependent manner after 24 hours. Still, after 48 hours, viral concentration started to increase at the lowest UV-C exposure.

However, viral concentration did not increase after 48 hours, once SARS-CoV-2 was exposed to the higher radiation doses (16.9 and 84.4 mJ/cm2).

The authors say the study shows that UV-C radiation achieves both inactivation and inhibition of SARS-CoV-2 in a dose-dependent manner.

Wednesday, Nov 25, 2020

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