key: cord-0865489-hrtt0cnd
authors: Chiappa, Federica; Frascella, Beatrice; Vigezzi, Giacomo Pietro; Moro, Matteo; Diamanti, Luca; Gentile, Leandro; Lago, Paolo; Clementi, Nicola; Signorelli, Carlo; Mancini, Nicasio; Odone, Anna
title: The efficacy of UV light-emitting technology against coronaviruses: a systematic review
date: 2021-05-21
journal: J Hosp Infect
DOI: 10.1016/j.jhin.2021.05.005
sha: e5272fe4f7cdd8ca2b055f835c43652d61573f77
doc_id: 865489
cord_uid: hrtt0cnd

BACKGROUND: The ongoing pandemic of COVID-19 has underlined the importance of adopting effective infection prevention and control (IPC) measures in hospital and community settings. UV-based technologies represent promising IPC tools: their effective application for sanitation has been extensively evaluated in the past but scant, heterogeneous and not conclusive evidence is available on their effect on SARS-CoV-2 transmission. METHODS: With the aim of pooling the available evidence on the efficacy of UV technologies against coronaviruses, we conducted a systematic review following PRISMA guidelines, searching Medline, Embase and Cochrane Library, and the main clinical trials’ registries (WHO ICTRP, ClinicalTrials.gov, Cochrane and EU Clinical Trial Register). Quantitative data on studies’ interventionS were summarized in tables, pooled by different coronavirus species and strain, UV source, characteristics of UV light exposure and outcomes. FINDINGS: Eighteen papers met our inclusion criteria, published between 1972 and 2020. Six focused on SARS-CoV-2, four on SARS-CoV-1, one on MERS-CoV, three on seasonal coronaviruses, and four on animal coronaviruses. All were experimental studies. Overall, despite wide heterocenicity within included studies, complete inactivation of coronaviruses on surfaces or aerosolized, including SARS-CoV-2, was reported to take a maximum exposure time of 15 minutes and to need a maximum distance from the UV emitter up to 1 meter. CONCLUSION: Advances in UV-based technologies in the field of sanitation and their proved high virucidal potential against SARS-CoV-2 support their use for IPC in hospital and community settings and their contribution towards ending the COVID-19 pandemic. National and international guidelines are to be updated and identify parameters and conditions of use to ensure both efficacy and safety of UV technology application for effective infection prevention and control in both healthcare and non-healthcare settings.

guidelines are to be updated and identify parameters and conditions of use to ensure both 51 efficacy and safety of UV technology application for effective infection prevention and control 52 in both healthcare and non-healthcare settings. 53 J o u r n a l P r e -p r o o f INTRODUCTION 54 Since the World Health Organization (WHO) declared the COVID-19 outbreak a 55 pandemic on 11 th March 2020, the global burden of COVID-19 has been massive with, at the 56 time of writing, over 119 million confirmed cases and over 2.6 million deaths across the world 57 [1, 2] . In such context, the adoption of effective infection prevention and control measures (IPC 58 measures) at the community and healthcare level is of utmost importance. SARS-CoV-2 59 infection is considered to be transmitted mainly via the respiratory route [3, 4] , direct and indirect 60 contact may also be important [5] . Data indicate that the virus can persist in the environment for 61 up to 72 hours on different materials [6-10]. Thus, it is crucial to identify effective microbicidal 62 approaches that can inform the design, use and evaluation of technologies supporting infection 63 control, with a particular focus on healthcare-associated outbreaks [11, 12] . 

Results from included studies assessing the efficacy of UV-based technologies on SARS-210

CoV-1 are reported in Table IV . On the other hand, in a study conducted by Kariwa et al. [42] , after 60 minutes exposure to 134 225 μW/cm 2 of UV light, the Hanoi strain of SARS-CoV-1 was still detectable (18.8 TCID50/ml). 226

Among the effective chemical and physical agents tested against SARS-CoV-1, there 228 were: sodium hypochlorite 0.05% and sodium hypochlorite 0,1% ( properties of HCoV-229E and HCoV-OC43, human coronaviruses responsible of seasonal 246 respiratory infections (Table IV) . When the samples suspended in 2% fetal calf serum were 247 exposed to a 60W UV emitter from a distance of 45 cm, the viral titer reduction curves were 248 convex, suggesting a "multi-hit" process of inactivation (229E <2 TCID50(log10)/0.2ml after 7 249 minutes, OC43 around 1 TCID50(log10)/0.2ml after 11 minutes). Based on this data, the 250 authors hypothesised that the original samples might contain clumps of the virus, possibly due to 251 the composition of the medium. Subsequently, they applied the same experimental conditions to 252 viral samples suspended in 0.2% bovine plasma albumin and found that the viral titer was 253 The UV sources were two UV LEDs systems; a circular one, emitting 279-nm or 297-nm UV 261 light, and a custom-made rectangular one, emitting 267-nm or 286-nm UV light. The stocks 262 were exposed at same distance and time, although not explicitly reported. The effective 263 inactivation of the virus was defined as the 3-log reduction after the exposure, also the reported 264 limit of quantification. All the UV wavelengths were proved to be effective in achieving this 265 reduction and, as the wavelength increases, the UV dose needed was 5.7, 7.0, 12.9 and 32.0 266 mJ/cm 2 , respectively. Particularly, the 267-nm UVC light determined the 3-log inactivation at the 267 lower UV dose. 268

Coronavirus strains 229E and OC43 growth were inhibited at 37°C in pH 7.4 [34] 270

(results of comparators are available in Appendix C). 271

Results from included studies' assessing the efficacy of UV-based technologies on animal 274 coronaviruses are reported in Table V . 275

Bedell et al.

[33] employed a triple UVC emitter to irradiate a dried MHV-A59 sample from a 276 distance of 122 cm. After 10 minutes, the viral titer was reduced to an undetectable level (6.11 277 log10 reduction), as shown by plaque counts. 278 MHV was also the object of a study conducted by Saknimit et al. [44] , in which the viral samples 279 were exposed to a 15 W UV emitter for 15 minutes from a distance of 1 m. They performed 280 plaque assays and found a decrease of infectivity titer to complete inactivation, which was >4.67 281 logPFU/0.1ml for MHV-2, and >3.34 logPFU/0.1ml for MHV-N. an 8W UV emitter, the samples were utterly inactivated, in 90 and 120 seconds, respectively. 295 We systematically retrieved and pooled all the available evidence on UV virucidal 311 properties against coronaviruses. We report that, albeit virus persistence was tested in different 312 experimental conditions with regard to UV exposure and sample preparation (dried sample, 313 liquid suspension and aerosolised), evidence suggests that UV light has a definite action on 314 coronaviruses titre reduction and inactivation. 315

The two main parameters that affect UV light efficacy and safety for environmental 316 disinfection are wavelength and dose. The dose is defined as UV energy received by a surface per 317 unit area (J/m 2 ) or, in other words, irradiance (W/m 2 ) multiplied by time. Irradiance, also 318 commonly called "light intensity", indicates the radiant flux (power) received by a surface per 319 unit area, and depends on the power of the UV source and the distance between the source and 320 the target surface: it increases proportionally to the emitted power, and decreases proportionally 321 to the square of the distance. At a specific wavelength, three additional parameters can affect UV 322 light efficacy, safety and applicability: i) exposure time, ii) UV power, and iii) distance between 323 the UV emitter and the target surfaces; ideally -to maintain UV effectiveness -the first two 324 should be as small as possible, and the latter the highest allowed. In conclusion, SARS-CoV-2 and coronaviruses are relatively easily inactivated by UV 402 light, even when aerosolized, and UV irradiation can be used as an adjunct to terminal cleaning 403 protocols in healthcare settings. UV light could be used on highly touched surfaces in crowded 404 spaces, where rapid and efficient disinfection of indoor environments is crucial to control the 405 spread of highly infective agents such as SARS-CoV-2. UVGI fixture designs for sanitization 406 technologies with high virucidal and energy efficiencies are quickly evolving, becoming more 407 effective while remaining safe. However, more evidence is needed to assess the clinical and cost 408 effectiveness, and user acceptability, of these technologies at healthcare and community levels. 

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