Abstract

The potential virucidal effects of UV-C irradiation on SARS-CoV-2 were experimentally evaluated for different illumination doses and virus concentrations (1000, 5, 0.05 MOI). At a virus density comparable to that observed in SARS-CoV-2 infection, an UV-C dose of just 3.7 mJ/cm2 was sufficient to achieve a more than 3-log inactivation without any sign of viral replication. Moreover, a complete inactivation at all viral concentrations was observed with 16.9 mJ/cm2. These results could explain the epidemiological trends of COVID-19 and are important for the development of novel sterilizing methods to contain SARS-CoV-2 infection.

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https://www.nature.com/articles/s41598-021-85425-w

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Abstract

Past experiments demonstrated SARS-CoV-2 inactivation by simulated sunlight; models have considered exclusively mechanisms involving UVB acting directly on RNA. However, UVA inactivation has been demonstrated for other enveloped RNA viruses, through indirect mechanisms involving the suspension medium. We propose a model combining UVB and UVA inactivation for SARS-CoV-2, which improves predictions by accounting for effects associated with the medium. UVA sensitivities deduced for SARS-CoV-2 are consistent with data for SARS-CoV-1 under UVA only. This analysis calls for experiments to separately assess effects of UVA and UVB in different media, and for including UVA in inactivation models.

Lay summary: Recent experiments have demonstrated that SARS-CoV-2 is inactivated by simulated sunlight; however, there are still many unknowns, including the mechanism of action and which part of the light spectrum is principally responsible. Our analysis indicates the need for targeted experiments that can separately assess the effects of UVA and UVB on SARS-CoV-2, and that sunlight inactivation models may need to be expanded to also include the effect of UVA. A first UVA-inclusive model is also proposed here. These findings have implications for how to improve the safety of the built environment, and for the seasonality of COVID-19.

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https://www.biorxiv.org/content/10.1101/2020.09.07.286666v1

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Abstract

The post Ultraviolet irradiation doses for coronavirus inactivation – Review & Analysis appeared first on Aeraze.

This book is a comprehensive source for technical information regarding ultraviolet germicidal irradiation (UVGI) and its application to air and surface disinfection for the control of pathogens and allergens. The primary focus is on airborne microbes and surface contamination applications for hospitals, commercial facilities, and residential homes.

All aspects of UVGI systems, including design methods, sizing methods, modeling, safety, installation, testing, guidelines, and disinfection theory are addressed in detail. An extensive database of over six hundred UV rate constant studies is included as well as tabular performance data for UV lamps and products. Providing this information in one single source simplifies the design and installation of UVGI systems, helps guarantee effective performance of new systems, and facilitates their use on a wide scale for the purpose of improving human health. This book is organized to provide systematic coverage of all related issues and will serve equally well as both a textbook and a handbook for general reference.

View book details:
https://www.springer.com/gp/book/9783642019982

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Summary

Background
Ultraviolet C (UVC) light has been used to inactivate several pathogens. Unlike conventional 254-nm UVC, 222-nm UVC is harmless to mammalian cells. Aim To investigate the disinfection efficacy of 222-nm UVC against human pathogens which are commonly found in the environment and healthcare facilities.

Methodology
Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica subsp. serovar Typhimurium, Campylobacter jejuni, Bacillus cereus (vegetative cells and endospores), Clostridium sporogenes (vegetative cells and endospores), Clostoridioides difficile (endospores), Candida albicans (yeast), Aspergillus niger (hyphae and spores), Trichophyton rubrum (hyphae and spores), feline calicivirus and influenza A virus were irradiated with 222-nm UVC at various doses. The remaining live bacterial and fungal cells, and viral infectivity were evaluated. The germicidal effect of 222-nm UVC was compared with that of 254-nm UVC.

Results
UVC with a wavelength of 222 nm had a potent germicidal effect on vegetative bacterial cells, yeast and viruses, and was as efficient as 245-nm UVC. In addition, 222-nm UVC had a more potent germicidal effect on bacterial endospores compared with 254-nm UVC. The fungicidal effect of 222-nm UVC against fungal spores and hyphae was weaker than that of 254-nm UVC.

Conclusions
UVC with a wavelength of 222 nm was able to inactivate a wide spectrum of microbial pathogens. In comparison with 254-nm UVC, the germicidal effect of 222-nm UVC for fungal hyphae and spores was low, but 222-nm UVC had a strong germicidal effect on bacterial endospores.

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https://www.journalofhospitalinfection.com/article/S0195-6701(20)30129-8/fulltext

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Abstract

Sun radiation consists of several spectrum regions, depending on the wavelengths, such as ultraviolet, visible and infrared portions. The ultraviolet rays (UV) are associated with both positive and negative effects on humans’ health. Ultraviolet light is used in the process of disinfection, it shows immunoregolatory activity and it stimulates vitamin D and serotonin production. It is well known that artificial sources of UVR are employed in the health field for sterilization procedures and for therapeutical purposes, such as treatment of dermatological pathologies like psoriasis, vitiligo and icterus neonatorum, as well as for aesthetic purposes (sunbed). In the last decade, besides these positive effects, UV side effects on skin have been demonstrated by different studies which correlated the intense and prolonged exposure to UV light with skin cancer development.

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https://air.unimi.it/bitstream/2434/244829/2/phd_unimi_R09586.pdf

The post Studio Dei Meccanismi Di Danno Da Raggi Uva E Uvb E Degli Effetti Protettivi Da Parte Di Composti Polifenolici In Sistemi appeared first on Aeraze.

Abstract

Antimicrobial violet-blue light is an emerging technology designed for enhanced clinical decontamination and treatment applications, due to its safety, efficacy and ease of use. This systematized review was designed to compile the current knowledge on the antimicrobial efficacy of 380-480 nm light on a range of health care and food-related pathogens including vegetative bacteria, bacterial endospores, fungi and viruses. Data were compiled from 79 studies, with the majority focussing on wavelengths in the region of 405 nm. Analysis indicated that Gram-positive and Gram-negative vegetative bacteria are the most susceptible organisms, while bacterial endospores, viruses and bacteriophage are the least. Evaluation of the dose required for a 1 log₁₀ reduction of key bacteria compared to population, irradiance and wavelength indicated that microbial titer and light intensity had little effect on the dose of 405 nm light required; however, linear analysis indicated organisms exposed to longer wavelengths of violet-blue light may require greater doses for inactivation. Additional research is required to ensure this technology can be used effectively, including: investigating inactivation of multidrug-resistant organisms, fungi, viruses and protozoa; further knowledge about the photodynamic inactivation mechanism of action; the potential for microbial resistance; and the establishment of a standardized exposure methodology.

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https://pubmed.ncbi.nlm.nih.gov/29350751/

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Resumen

Las lámparas excimer de descarga de barrera dieléctrica (DBD), son modeladas como cargas capacitivas y requieren de fuentes de alimentación de alto voltaje para establecer la descarga en el gas. Debido a la baja capacitancia de la lámpara, la operación de la fuente es afectada por las capacitancias parasitas de sus componentes. Con el fin de entender los efectos de las capacitancias y seleccionar un convertidor óptimo, este proyecto presenta el análisis teórico del convertidor resonante boost considerando las capacitancias de los interruptores y el impacto de la relación de transformación en la eficiencia del sistema. El convertidor óptimo es implementado y utilizado para la validación experimental.

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https://repository.javeriana.edu.co/handle/10554/19614

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Abstract

The spread of novel coronavirus disease 2019 (COVID-19) infections worldwide has raised concerns about the prevention and control of SARS-CoV-2. Devices that rapidly inactivate viruses can reduce the chance of infection through aerosols and contact transmission. This in vitro study demonstrated that irradiation with a deep ultraviolet light-emitting diode (DUV-LED) of 280 ± 5 nm wavelength rapidly inactivates SARS-CoV-2 obtained from a COVID-19 patient. Development of devices equipped with DUV-LED is expected to prevent virus invasion through the air and after touching contaminated objects.

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7473214/

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Abstract

The SARS-CoV-2 pandemic urges for cheap, reliable and rapid technologies for disinfection and decontamination. We here evaluated the efficiency of UV-C irradiation to inactivate surface dried SARS-CoV-2. Drying for two hours did not have a major impact on the infectivity of SARS-CoV-2, indicating that exhaled virus in droplets or aerosols stays infectious on surfaces at least for a certain amount of time. Strikingly, short exposure of high titer surface dried virus (3*10^6 IU/ml) with UV-C light (0.66 mJ/cm2) resulted in a total reduction of SARS-CoV-2 infectivity. Together, our results demonstrate that SARS-CoV-2 is rapidly inactivated by relatively low doses of UV-C irradiation. Hence, UV-C treatment is an effective non-chemical possibility to decontaminate surfaces from high-titer infectious SARS-CoV-2.

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https://www.biorxiv.org/content/10.1101/2020.09.22.308098v1

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