Exploring the Differences in the Response of SARS-CoV-2 Delta and Omicron to Ultraviolet Radiation

One method that canhelp slow the spread of coronaviruses is disinfectionwith UV light. The Delta and Omicron variants of the COVID-19 virus(SARS-CoV-2) have come to dominate the later stages of the pandemicdue to their higher rates of transmission. In this work, it is shownthat a 17% higher UV254 dose is required for the disinfectionof Delta and Omicron variants when compared to the ancestral strainof SARS-CoV-2. The UV254 disinfection rate constants forSARS-CoV-2 and the Delta and Omicron variants were found to be 1.4 & PLUSMN; 0.3, 1.1 & PLUSMN; 0.2, and 1.1 & PLUSMN; 0.2 cm(2)/mJ,respectively. The rate constants of Delta and Omicron were statisticallydifferent from the ancestral strain of SARS-CoV-2 at the 95% confidencelevel based on at least three replicate experiments. It is suggestedthat the reason for this difference is the absence of repeating uracil(U) bases in the genome of the two variants. The UV254 sensitivityof repeating pyrimidine bases is well-established. There are 2.6 and3.7% fewer uracil triplets (UUU) in the Delta and Omicron variants,respectively, when compared to SARS-CoV-2. This difference in UV254 sensitivity is relevant to a range of UV disinfection applicationsincluding upper-room disinfection, air handling equipment, aircraftsanitization, and others.