Genomic Modeling as an Approach to Identify Surrogates for Use in Experimental Validation of SARS-CoV-2 and HuNoV Inactivation by UV-C Treatment

Abstract

Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic that continues to pose significant public health concerns. While research to deliver vaccines and antivirals are being pursued, various effective technologies to control its environmental spread are also being targeted. Ultraviolet light (UV-C) technologies are effective against a broad spectrum of microorganisms when used even on large surface areas. In this study, we developed a pyrimidine dinucleotide frequency based genomic model to predict the sensitivity of select enveloped and non-enveloped viruses to UV-C treatments in order to identify potential SARS-CoV-2 and human norovirus surrogates. The results revealed that this model was best fitted using linear regression with r 2 = 0.90. The predicted UV-C sensitivity ( D 90 – dose for 90% inactivation) for SARS-CoV-2 and MERS-CoV was found to be 21.5 and 28 J/m 2 , respectively (with an estimated 18 J/m 2 obtained from published experimental data for SARS-CoV-1), suggesting that coronaviruses are highly sensitive to UV-C light compared to other ssRNA viruses used in this modeling study. Murine hepatitis virus (MHV) A59 strain with a D 90 of 21 J/m 2 close to that of SARS-CoV-2 was identified as a suitable surrogate to validate SARS-CoV-2 inactivation by UV-C treatment. Furthermore, the non-enveloped human noroviruses (HuNoVs), had predicted D 90 values of 69.1, 89, and 77.6 J/m 2 for genogroups GI, GII, and GIV, respectively. Murine norovirus (MNV-1) of GV with a D 90 = 100 J/m 2 was identified as a potential conservative surrogate for UV-C inactivation of these HuNoVs. This study provides useful insights for the identification of potential non-pathogenic (to humans) surrogates to understand inactivation kinetics and their use in experimental validation of UV-C disinfection systems. This approach can be used to narrow the number of surrogates used in testing UV-C inactivation of other human and animal ssRNA viral pathogens for experimental validation that can save cost, labor and time.

SARS-CoV-2 disinfection in aqueous solution by UV222 from a krypton chlorine excilamp

“…Considering these limitations, these data provide a strong foundation for future development and application of UV222 for reducing airborne viral transmission. UV222 is both 4.2 times safer for human exposure (the threshold limit values for human UV exposure are mJ/cm 2 and mJ/cm 2 at and nm, respectively ) and at least 1.3 times as effective at disinfecting SARS-CoV-2 (the D90 we observed for UV222 (1.6 mJ/cm 2 ) is lower than recently predicted by genomic modeling for UV254 (2.15 mJ/cm ) 42 ). A recent study applying continuous UV222 at doses below these threshold limit values to treat other airborne coronaviruses demonstrated multiple logs of inactivation within minutes 43 .…”

Pulsed Broad-Spectrum UV Light Effectively Inactivates SARS-CoV-2 on Multiple Surfaces and N95 Material

“…While only a single device was tested in this study, a variety of UV inactivation studies have been published focusing on SARS-CoV-2 and other coronaviruses using different wavelengths and environmental conditions [30,31,[41][42][43][44][45]. In contrast to the broad-spectrum UV device tested here, most UV devices that have been tested for efficacy against SARS-CoV-2 produce constant, non-pulsed UV-C (222-300 nm) light exclusively [28,[30][31][32][33].…”

Pulsed broad-spectrum UV light effectively inactivates SARS-CoV-2 on multiple surfaces

“…The effectiveness of UV light, pulsed or constant, in inactivating pathogens is expected to be directly related to the dosage applied [33]. Here, we have described empirically determined dosages of broad-spectrum, pulsed UV light that are effective for the inactivation of SARS-CoV- While only a single device was tested in this study, a variety of UV inactivation studies have been published focusing on SARS-CoV-2 and other coronaviruses using different wavelengths and environmental conditions [38][39][40][41][42][43]. This has led to the development of new UV disinfection products in an effort to address proper disinfection of PPE and surfaces as the pandemic continues [44].…”