Systematic evaluating and modeling of SARS-CoV-2 UVC disinfection

Area of Science:

• Microbiology and Virology
• Photochemistry and Photobiology
• Public Health and Epidemiology

Background:

• The COVID-19 pandemic highlighted the need for effective disinfection strategies in public spaces.
• Ultraviolet (UV) radiation is a promising technology for inactivating pathogens, but its efficacy against SARS-CoV-2 requires detailed investigation across different wavelengths and conditions.
• Understanding the influence of environmental factors on UV disinfection is crucial for optimizing its application.

Purpose of the Study:

• To evaluate the effectiveness of different UV wavelengths (222 nm, 254 nm, 265 nm) in inactivating SARS-CoV-2 under various conditions.
• To investigate the impact of suspension media composition (e.g., PBS, cell culture medium) and specific components (amino acids, vitamins) on UV disinfection efficiency.
• To assess the performance of UV light on N95 masks and explore the safety of 222 nm UV radiation.

Main Methods:

• SARS-CoV-2 infectivity reduction assays were performed using specific doses of UV light (254 nm, 222 nm, 265 nm) applied to viral suspensions in different media (PBS, EMEM with FBS).
• Viral susceptibility to UV radiation was quantified, and the attenuating effects of media components were analyzed.
• A disinfection model was developed to correlate liquid absorbance with viral susceptibility across different UV wavelengths.
• Mechanical properties of human skin (stratum corneum) were assessed after exposure to 222 nm UV radiation.

Main Results:

• A 3-log reduction of SARS-CoV-2 infectivity was achieved with 12.5 mJ/cm² of 254 nm UV in PBS, but 25 mJ/cm² was needed in cell culture medium.
• SARS-CoV-2 susceptibility was 4.4-fold greater in PBS compared to cell culture medium, with significant attenuation by amino acids, vitamins, and niacinamide.
• 222 nm UV was most effective in low-absorbing liquids and on N95 masks, while 265 nm UV was more effective in high-absorbing liquids.
• No significant changes in skin mechanical properties were observed below 50 J/cm² of 222 nm UV exposure.

Conclusions:

• The effectiveness of UV disinfection against SARS-CoV-2 is highly dependent on the suspension medium, necessitating application-specific dosage determination.
• Different UV wavelengths exhibit distinct efficacy profiles influenced by environmental factors, with 222 nm showing promise for specific applications like mask disinfection.
• Careful consideration of UV dosage is essential to balance disinfection efficacy with potential risks, particularly concerning human skin exposure.