A new research study shows that a safe UV disinfection system effectively kills coronavirus.

Recent studies have reported that SARS-CoV-2 can survive on surfaces for several days and that hospitals may be a potential source of transmission due to contaminated surfaces. With an aim to slow the spread of COVID-19, a recent study investigated the effectiveness of UV disinfection on surfaces contaminated with SARS-CoV-2.

Increasingly used in healthcare to prevent the spread of healthcare-associated infections, UV disinfection systems most commonly emit UV radiation C (UVC) of around 254nm – but this is harmful to the skin and eyes. Previous studies have identified that 222-nm UVC light, belonging to far-UVC (207-222 nm), is less harmful but has the same disinfection properties. Despite this, prior studies involving 222 nm UVC light have only looked at how it can kill other seasonal coronaviruses, not directly at SARS-CoV-2.

Published in the American Journal of Infection Control, researchers from Hiroshima University conducted a study using Ushio’s Care222TM krypton-chloride excimer lamp. Sterile polystyrene plates were covered with a 100 microliter solution containing the coronavirus. After drying in a biosafety cabinet at room temperature, a Far-UVC lamp was placed 24 centimetres above the surface of the plates. The radiation intensity at the surface was 0.1 mW/cm2. After the treatment, the plates were analysed for presence of live virus.

The study reported that 99.7% of the SARS-CoV-2 coronavirus was killed after a 30-second exposure to 222 nm UVC irradiation at 0.1 mW/cm2. 

The 254 nm UVC germicidal lamps that are currently used to disinfect healthcare facilities are harmful to the skin and eyes. This means they can only be used in an empty room. A wavelength of 222 nm UVC is much safer and does not cause damage to the skin and eyes like the 254 nm wavelength. The researchers suggest that a 222-nm UVC disinfection system could be safely used in occupied public spaces. 

With a requirement to help slow the spread of SARS-CoV-2 through prevention and control practices, such as UV disinfection, this study is a positive step forward. However, the researchers identify that further studies are necessary to evaluate the safety and effectiveness of 222 nm UVC irradiation in killing SARS-CoV-2 viruses on surfaces in real-world settings.

Written by Helen Massy, BSc

References:

Kitagawa, H., Nomura, T., Nazmul, T., Omori, K., Shigemoto, N., Sakaguchi, T. and Ohge, H., 2020. Effectiveness of 222-nm ultraviolet light on disinfecting SARS-CoV-2 surface contamination. American Journal of Infection Control.

EurekAlert!. 2020. Study Shows First Proof That A Safer UV Light Effectively Kills Virus Causing COVID-19. [online] Available at: [Accessed 21 September 2020].

Image by Thor Deichmann from Pixabay