This UVC Wavelength Is Most Effective In Coronavirus Deactivation (Medicine)

Qunxiang Ong and colleagues in their recent paper carried out study on the efficacy of different UVC wavelengths on inactivation of coronavirus. They found that, 277-nm UVC LED is most effective in viral inactivation, followed by 254-nm UVC mercury lamp.

Several studies have studied the sensitivity of different microbes to UVC wavelengths, including human coronaviruses and SARS-CoV-2. However, no study to date has performed a direct comparative study on the efficacy of different UVC wavelengths on inactivation of coronaviruses. In addition, mechanistic insight into how different UVC wavelengths inactivate coronaviruses is severely lacking, and greater understanding in this area would facilitate their deployment in future pandemics.

Now, Qunxiang Ong and colleagues carried out study on the efficacy of different UVC wavelengths on inactivation of coronavirus. In order to examine the inactivation efficacy of UVC on human coronavirus, hCoV-OC43 and hCoV-229E, they placed virus on plastic petri dishes and exposed it to various UVC wavelengths of 73 µW/cm² for different timings ranging from 30 to 300 seconds.

They observed reduction in infectivity of hCoV-OC43 and hCoV-229E after exposure to different UVC irradiation. The 277-nm UVC LED was most effective in carrying out the inactivation and achieved 3-log inactivation at 22 mJ/cm² for both human coronavirus strains, whereas 254-nm UV lamp achieved only 2-log inactivation for hCoV-OC43 and 1-log inactivation for hCoV-229E with same dosage. In addition, it has been found that, 222-nm UVC LED does not affect the genomic material of beta-coronavirus, which was claimed in previous study.

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Fig 1: Inactivation of human coronaviruses after exposure to different UVC wavelengths: Infection of human lung cell line, HCT-8 from irradiated and untreated hCoV-OC43. Green fluorescence indicates infected cells while blue fluorescence indicates DAPI stains of nuclei. Images were acquired with a 40x objective, with the scale bars at 50 µm © Qunxiang Ong

Finally, mechanistic studies suggested that, 277 nm UVC LED’s higher efficacy at inactivation of corona virus is not achieved via UV-induced genomic damage, but this is achieved via a combination of photo-degradation of spike proteins and RNA molecules.

“While UVC mercury lamp is more effective in degrading viral genomic content compared to 277-nm UVC LED, the latter results in a pronounced photo-degradation of spike proteins which potentially contributed to the higher efficacy of coronavirus inactivation. Hence, inactivation of coronaviruses by 277-nm UVC LED irradiation constitutes a more promising method for disinfection.”

Reference: Qunxiang Ong, J.W. Ronnie Teo, Joshua Dela Cruz, Elijah Wee, Winson Wee, Weiping Han, “Irradiation of UVC LED at 277 nm inactivates coronaviruses by photodegradation of spike protein”, bioRxiv 2021.05.31.446403; doi:

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