Susceptibility of SARS-CoV-2 to UV irradiation

Comparison of the inactivation capacity of various UV wavelengths on SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a worldwide pandemic. Ultraviolet (UV) is regarded as a very powerful tool against SARS-CoV-2. However, the inactivating effects of different UV wavelengths on SARS-CoV-2 under the same conditions have hardly been compared. Here, we showed that SARS-CoV-2 cultured in Dulbecco's modified Eagle's medium and 2% fetal bovine serum was efficiently inactivated by irradiation with 222, 254, and 265 wavelengths UV, but not at 308 nm. In addition, it was revealed that UV absorption by DMEM-2% FBS is very efficient at 222 nm. Our results present potentially important information for selecting the optimum UV wavelength according to the application.

Inactivation methods for human coronavirus 229E on various food-contact surfaces and foods

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the cause of the COVID-19 outbreaks, is transmitted by respiratory droplets and has become a life-threatening viral pandemic worldwide. The aim of this study was to evaluate the effects of different chemical (chlorine dioxide [ClO2] and peroxyacetic acid [PAA]) and physical (ultraviolet [UV]-C irradiation) inactivation methods on various food-contact surfaces (stainless steel [SS] and polypropylene [PP]) and foods (lettuce, chicken breast, and salmon) contaminated with human coronavirus 229E (HCoV-229E). Treatments with the maximum concentration of ClO2 (500 ppm) and PAA (200 ppm) for 5 min achieved >99.9% inactivation on SS and PP. At 200 ppm ClO2 for 1 min on lettuce, chicken breast, and salmon, the HCoV-229E titers were 1.19, 3.54, and 3.97 log10 TCID50/mL, respectively. Exposure (5 min) to 80 ppm PAA achieved 1.68 log10 reduction on lettuce, and 2.03 and 1.43 log10 reductions on chicken breast and salmon, respectively, treated with 1500 ppm PAA. In the carrier tests, HCoV-229E titers on food-contact surfaces were significantly decreased (p < 0.05) with increased doses of UV-C (0-60 mJ/cm2) and not detected at the maximum UV-C dose (Detection limit: 1.0 log10 TCID50/coupon). The UV-C dose of 900 mJ/cm2 proved more effective on chicken breast (>2 log10 reduction) than on lettuce and salmon (>1 log10 reduction). However, there were no quality changes (p > 0.05) in food samples after inactivation treatments except the maximum PAA concentration (5 min) and the UV-C dose (1800 mJ/cm2).

Ultrafast inactivation of SARS-CoV-2 with 266 nm lasers

Disinfection eliminates pathogenic microorganisms and ensures a biosafe environment for human beings. The rapid spread of COVID-19 is challenging traditional disinfection methods in terms of reducing harmful side effects and conducting faster processes. Spraying large-scale chemical disinfectants is harmful to individuals and the environment, while UV lamp and light-emitting diode (LED) disinfection still requires a long exposure time due to the low irradiance and highly divergent beam characteristics. Given that a laser maintains a high irradiance over a long distance, we studied the effectiveness of lasers as a new disinfection method, and the results show the capability for ultrafast inactivation of SARS-CoV-2 virus with a 266 nm laser. This work confirms UV lasers as a good candidate for disinfection.

Proposing the n+-AlGaN tunnel junction for an efficient deep-ultraviolet light-emitting diode at 254 nm emission

Toxic and low-pressure deep-ultraviolet (DUV) mercury lamps have been used widely for applications of surface disinfection and water sterilization. The exposure of pathogens to 254 nm DUV radiations has been proven to be an effective and environmentally safe way to inactivate germs as well as viruses in short time. To replace toxic mercury DUV lamps, an n ⁺-A l G a N tunnel junction (TJ)-based DUV light-emitting diode (LED) at 254 nm emission has been investigated. The studied conventional LED device has maximum internal quantum efficiency (IQE) of 50% with an efficiency droop of 18% at 200A/c m ². In contrast, the calculated results show that a maximum IQE of 82% with a 3% efficiency droop under a relatively higher injection current was estimated by employing a 5 nm thin n ⁺-A l G a N TJ with a 0.70 aluminum molar fraction. In addition, the TJ LED emitted power has been improved significantly by 2.5 times compared with a conventional LED structure. Such an efficient n ⁺-A l G a N TJ-based DUV LED at 254 nm emission might open a new way, to the best of our knowledge, for the development of safe and efficient germicidal irradiation sources.

Implication of cell culture methods and biases on UV inactivation of viruses

Inactivation of human respiratory viruses in air and on surfaces is important to control their spread. Exposure to germicidal ultraviolet (UV-C) light damages viral nucleic acid rendering them non-infectious. Most of the recent viral inactivation studies have not considered potential artifacts caused by interactions between UV-C light and culture media used to suspend and deposit virus on surfaces. We show that the reactive oxygen and nitrogen species (ROS and RNS) form when commonly used virus culture media is exposed to 265 nm irradiation from light emitting diodes (LEDs) at UV-C doses (4 or 40 mJ/cm²) commonly considered to achieve multiple log-inactivation of virus. Surface viral inactivation values were enhanced from 0.49 to 2.92 log₁₀ of viruses in DMEM, EMEM or EMEM-F as compared to absence of culture media (only suspended in Tris-buffer). The mechanisms responsible for the enhanced surface inactivate is hypothesized to involve photo-activation of vitamins and dyes present in the culture media, deposited with the virus on surfaces to be disinfected, which produce ROS and RNS. Given the rapidly growing research and commercial markets for UV-C disinfecting devices, there is a need to establish surface disinfecting protocols that avoid viral inactivation enhancement artifacts associated with selection and use of common cell culture media in the presence of UV-C light. This study addresses this weak link in the literature and highlights that inadequate selection of virus suspension media may cause a bias (i.e., over-estimation) for the UV-C dosages required for virus inactivation on surfaces.

Design of UVC Surface Disinfection Robot with Coverage Path Planning Using Map-Based Approach At-The-Edge

In response to the issue of virus contamination in the cold-chain warehouse or hospital environment under the influence of the COVID-19, we propose the design work of a disinfection robot based on the UVC radiation mechanism using the low-computational path optimization at-the-edge. To build a surface disinfection robot with less computing power to generate a collision-free path with shorter total distance in studies, a 2D map is used as a graph-based approach to automatically generate a closed-loop disinfection path to cover all the accessible surfaces. The discrete disinfection points from the map are extracted with effective disinfection distances and sorted by a nearest-neighbor (NN) search over historical trajectory data and improved A * algorithm to obtain an efficient coverage path to all accessible boundaries of the entire area. The purpose of improved A * algorithm with NN is not to find the optimal path solution but to optimize one with reasonable computing power. The proposed algorithm enhances the path-finding efficiency by a dynamically weighted heuristic function and reduces the path turning angles, which improves the path smoothness significantly requiring less computing power. The Gazebo simulation is conducted, and the prototype disinfection robot has been built and tested in a real lab environment. Compared with the classic A * algorithm, the improved A * algorithm with NN has improved the path-finding efficiency and reduced the path length while covering the same area. Both the simulation and experimental results show that this approach can provide the design to balance the tradeoffs among the path-finding efficiency, smoothness, disinfection coverage, and computation resources.

Pulsed-Xenon Ultraviolet Light Highly Inactivates Human Coronaviruses on Solid Surfaces, Particularly SARS-CoV-2

In the context of ongoing and future pandemics, non-pharmaceutical interventions are critical in reducing viral infections and the emergence of new antigenic variants while the population reaches immunity to limit viral transmission. This study provides information on efficient and fast methods of disinfecting surfaces contaminated with different human coronaviruses (CoVs) in healthcare settings. The ability to disinfect three different human coronaviruses (HCoV-229E, MERS-CoV, and SARS-CoV-2) on dried surfaces with light was determined for a fully characterized pulsed-xenon ultraviolet (PX-UV) source. Thereafter, the effectiveness of this treatment to inactivate SARS-CoV-2 was compared to that of conventional low-pressure mercury UVC lamps by using equivalent irradiances of UVC wavelengths. Under the experimental conditions of this research, PX-UV light completely inactivated the CoVs tested on solid surfaces since the infectivity of the three CoVs was reduced up to 4 orders of magnitude by PX-UV irradiation, with a cumulated dose of as much as 21.162 mJ/cm² when considering all UV wavelengths (5.402 mJ/cm² of just UVC light). Furthermore, continuous irradiation with UVC light was less efficient in inactivating SARS-CoV-2 than treatment with PX-UV light. Therefore, PX-UV light postulates as a promising decontamination measure to tackle the propagation of future outbreaks of CoVs.

Disinfection and decontamination in the context of SARS-CoV-2-specific data

Given the high transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as witnessed early in the coronavirus disease 2019 (COVID-19) pandemic, concerns arose with the existing methods for virus disinfection and decontamination. The need for SARS-CoV-2-specific data stimulated considerable research in this regard. Overall, SARS-CoV-2 is practically and equally susceptible to approaches for disinfection and decontamination that have been previously found for other human or animal coronaviruses. The latter have included techniques utilizing temperature modulation, pH extremes, irradiation, and chemical treatments. These physicochemical methods are a necessary adjunct to other prevention strategies, given the environmental and patient surface ubiquity of the virus. Classic studies of disinfection have also allowed for extrapolation to the eradication of the virus on human mucosal surfaces by some chemical means. Despite considerable laboratory study, practical field assessments are generally lacking and need to be encouraged to confirm the correlation of interventions with viral eradication and infection prevention. Transparency in the constitution and use of any method or chemical is also essential to furthering practical applications.

Global occurrence of SARS-CoV-2 in environmental aquatic matrices and its implications for sanitation and vulnerabilities in Brazil and developing countries

This paper includes a systematic review of the SARS-CoV-2 occurrence in environmental aquatic matrices and a critical sanitation analysis. We discussed the interconnection of sanitation services (wastewater, water supply, solid waste, and stormwater drainage) functioning as an important network for controlling the spread of SARS-CoV-2 in waters. We collected 98 studies containing data of the SARS-CoV-2 occurrence in aquatic matrices around the world, of which 40% were from developing countries. Alongside a significant number of people infected by the virus, developing countries face socioeconomic deficiencies and insufficient public investment in infrastructure. Therefore, our study focused on highlighting solutions to provide sanitation in developing countries, considering the virus control in waters by disinfection techniques and sanitary measures, including alternatives for the vulnerable communities. The need for multilateral efforts to improve the universal coverage of sanitation services demands urgent attention in a pandemic scenario.

Viral inactivation by light

Nowadays, viral infections are one of the greatest challenges for medical sciences and human society. While antiviral compounds and chemical inactivation remain inadequate, physical approaches based on irradiation provide new potentials for prevention and treatment of viral infections, without the risk of drug resistance and other unwanted side effects. Light across the electromagnetic spectrum can inactivate the virions using ionizing and non-ionizing radiations. This review highlights the anti-viral utility of radiant methods from the aspects of ionizing radiation, including high energy ultraviolet, gamma ray, X-ray, and neutron, and non-ionizing photo-inactivation, including lasers and blue light.

Reagentless Quantum-Rate-Based Electrochemical Signal of Graphene for Detecting SARS-CoV-2 Infection Using Nasal Swab Specimens

The quantum-rate model predicts a rate k as a frequency for transporting electrons within molecular structures, which is governed by the ratio between the quantum of conductance G and capacitance C_q, such that k = G/C_q. This frequency, as measured in a single-layer graphene appropriately modified with suitable biological receptors, can be applied as a transducer signal that ranges sensitivities within the attomole for biosensing applications. Here, we applied this label-free and reagentless biosensing transducer signal methodology for the qualitative diagnosis of COVID-19 infections, where this assay methodology was shown to be similar to the gold-standard real-time polymerase chain reaction. The quantum-rate strategy for the diagnosis of COVID-19 was performed by combining the response of the interface for detecting the S and N proteins of SARS-CoV-2 virus as accessed from nasopharyngeal/oropharyngeal patient samples with 80% of sensitivity and 77% of specificity. As a label-free and reagentless biosensing platform, the methodology is decidedly useful for point-of-care and internet-of-things biological assaying technologies, not only because of its real-time ability to measure infections but also because of the capability for miniaturization inherent in reagentless electrochemical methods. This approach effectively permits the rapid development of biological assays for surveillance and control of endemics and pandemics.

The Bovine Seminal Plasma Protein PDC-109 Possesses Pan-Antiviral Activity

Mammalian seminal plasma contains a multitude of bioactive components, including lipids, glucose, mineral elements, metabolites, proteins, cytokines, and growth factors, with various functions during insemination and fertilization. The seminal plasma protein PDC-109 is one of the major soluble components of the bovine ejaculate and is crucially important for sperm motility, capacitation, and acrosome reaction. A hitherto underappreciated function of seminal plasma is its anti-microbial and antiviral activity, which may limit the sexual transmission of infectious diseases during intercourse. We have recently discovered that PDC-109 inhibits the membrane fusion activity of influenza virus particles and significantly impairs viral infections at micromolar concentrations. Here we investigated whether the antiviral activity of PDC-109 is restricted to Influenza or if other mammalian viruses are similarly affected. We focused on Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), the etiological agent of the Coronavirus Disease 19 (COVID-19), thoroughly assessing PDC-109 inhibition with SARS-CoV-2 Spike (S)-pseudotyped reporter virus particles, but also live-virus infections. Consistent with our previous publications, we found significant virus inhibition, albeit accompanied by substantial cytotoxicity. However, using time-of-addition experiments we discovered a treatment regimen that enables virus suppression without affecting cell viability. We furthermore demonstrated that PDC-109 is also able to impair infections mediated by the VSV glycoprotein (VSVg), thus indicating a broad pan-antiviral activity against multiple virus species and families.

Does climate help modeling COVID-19 risk and to what extent?

A growing number of studies suggest that climate may impact the spread of COVID-19. This hypothesis is supported by data from similar viral contagions, such as SARS and the 1918 Flu Pandemic, and corroborated by US influenza data. However, the extent to which climate may affect COVID-19 transmission rates and help modeling COVID-19 risk is still not well understood. This study demonstrates that such an understanding is attainable through the development of regression models that verify how climate contributes to modeling COVID-19 transmission, and the use of feature importance techniques that assess the relative weight of meteorological variables compared to epidemiological, socioeconomic, environmental, and global health factors. The ensuing results show that meteorological factors play a key role in regression models of COVID-19 risk, with ultraviolet radiation (UV) as the main driver. These results are corroborated by statistical correlation analyses and a panel data fixed-effect model confirming that UV radiation coefficients are significantly negatively correlated with COVID-19 transmission rates.

Rapid SARS-CoV-2 disinfection on distant surfaces with UV-C: The inactivation is affected by the type of material

SARS-CoV-2 is responsible for the COVID-19 pandemic, which has caused almost 570 million infections and over six million deaths worldwide. To help curb its spread, solutions using ultraviolet light (UV) for quick virus inactivation inside buildings without human intervention could be very useful to reduce chances of contagion. The UV dose must be sufficient to inactivate the virus considering the different materials in the room, but it should not be too high, not to degrade the environment. In the present study, we have analyzed the ability of a 254 nm wavelength UV-C lamp to inactivate dried samples of SARS-CoV-2 exposed at a distance of two meters, simulating a full-scale scenario. Our results showed that virus inactivation was extremely efficient in most tested materials, which included plastic, metal, wood, and textile, with a UV-C exposure of only 42 s (equivalent to 10 mJ/cm²). However, porous materials like medium density fibreboard, were hard to decontaminate, indicating that they should be avoided in hospital rooms and public places.

UV-C irradiation-based inactivation of SARS-CoV-2 in contaminated porous and non-porous surfaces

The SARS-CoV-2 pandemic emphasized effective cleaning and disinfection of common spaces as an essential tool to mitigate viral transmission. To address this problem, decontamination technologies based on UV-C light are being used. Our aim was to generate coherent and translational datasets of effective UV-C-based SARS-CoV-2 inactivation protocols for the application on surfaces with different compositions. Virus infectivity after UV-C exposure of several porous (bed linen, various types of upholstery, synthetic leather, clothing) and non-porous (types of plastic, stainless steel, glass, ceramics, wood, vinyl) materials was assessed through plaque assay using a SARS-CoV-2 clinical isolate. Studies were conducted under controlled environmental conditions with a 254-nm UV-C lamp and irradiance values quantified using a 254 nm-calibrated sensor. From each material type (porous/non-porous), a product was selected as a reference to assess the decrease of infectious virus particles as a function of UV-C dose, before testing the remaining surfaces with selected critical doses. Our data show that UV-C irradiation is effectively inactivating SARS-CoV-2 on both material types. However, an efficient reduction in the number of infectious viral particles was achieved much faster and at lower doses on non-porous surfaces. The treatment effectiveness on porous surfaces was demonstrated to be highly variable and composition-dependent. Our findings will support the optimization of UV-C-based technologies, enabling the adoption of effective customizable protocols that will help to ensure higher antiviral efficiencies.

Review of Method and a New Tool for Decline and Inactive SARS-CoV-2 in Wastewater Treatment

Following the recent outbreak of the COVID-19 pandemic caused by the SARS-CoV-2 virus, monitoring sewage has become crucial, according to reports that the virus was detected in sewage. Currently, various methods are discussed for understanding the SARS-CoV-2 using wastewater surveillance. This paper first introduces the fundamental knowledge of primary, secondary, and tertiary water treatment on SARS-CoV-2. Next, a thorough overview is presented to summarize the recent developments and breakthroughs in removing SARS-CoV-2 using solar water disinfection (SODIS) and UV (UVA (315–400 nm), UVB (280-315 nm), and UVC (100–280 nm)) process. In addition, Due to the fact that the distilled water can be exposed to sunlight if there is no heating source, it can be disinfected using solar water disinfection (SODIS). SODIS, on the other hand, is a well-known method of reducing pathogens in contaminated water; moreover, UVC can inactivate SARS-CoV-2 when the wavelength is between 100 to 280 nanometers. High temperatures (more than 56°C) and UVC are essential for eliminating SARS-CoV-2; however, the SODIS systems use UVA and work at lower temperatures (less than45°C). Therefore, using SODIS methods for wastewater treatment (or providing drinking water) is not appropriate during a situation like the ongoing pandemic. Finally, a wastewater-based epidemiology (WBE) tracking tool for SARS-CoV-2 can be used to detect its presence in wastewater.

Coronaviruses are stable on glass, but are eliminated by manual dishwashing procedures

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is primarily transmitted from human to human via droplets and aerosols. While transmission via contaminated surfaces is also considered possible, the overall risk of this transmission route is assumed to be low. Nevertheless, transmission through contaminated drinking glasses may pose an increased risk as the glass is in direct contact with the mouth and oral cavity. Using human coronavirus 229E (HCoV-229E) as surrogate for SARS-CoV-2, this study examined coronavirus stability on glass, inactivation by dishwashing detergents, and virus elimination by a manual glass scrubbing device. Infectious HCoV-229E was recovered from glass for 7 and 21 days of storage under daylight and dark conditions, respectively. Near complete inactivation of HCoV-229E (>4 log10 reduction) was observed after incubation with two common dishwashing detergents at room temperature for 15 s, whereas incubation at 43 °C for 60 s was necessary for a third detergent to achieve a similar titer reduction. The virus was efficiently removed from contaminated drinking glasses using a manual glass scrubbing device in accordance with German standard DIN 6653-3. The results confirm that coronaviruses are relatively stable on glass, but indicate that common manual dishwashing procedures can efficiently eliminate coronaviruses from drinking glasses.

Inactivation of aerosolized SARS-CoV-2 by 254 nm UV-C irradiation

Surface residing SARS-CoV-2 is efficiently inactivated by UV-C irradiation. This raises the question whether UV-C-based technologies are also suitable to decontaminate SARS-CoV-2- containing aerosols and which doses are needed to achieve inactivation. Here, we designed a test bench to generate aerosolized SARS-CoV-2 and exposed the aerosols to a defined UV-C dose. Our results demonstrate that the exposure of aerosolized SARS-CoV-2 with a low average dose in the order of 0.42-0.51 mJ/cm2 UV-C at 254 nm resulted in more than 99.9% reduction in viral titers. Altogether, UV-C-based decontamination of aerosols seems highly effective to achieve a significant reduction in SARS-CoV-2 infectivity.

Cellular and Humoral Immunity against Different SARS-CoV-2 Variants Is Detectable but Reduced in Vaccinated Kidney Transplant Patients

In kidney transplant (KTX) patients, immune responses after booster vaccination against SARS-CoV-2 are inadequately examined. We analyzed these patients a median of four months after a third/fourth vaccination and compared them to healthy controls. Cellular responses were analyzed by interferon-gamma (IFN-γ) and interleukin-2 (IL-2) ELISpot assays. Neutralizing antibody titers were assessed against SARS-CoV-2 D614G (wild type) and the variants alpha, delta, and omicron by a cell culture-based neutralization assay. Humoral immunity was also determined by a competitive fluorescence assay, using 11 different variants of SARS-CoV-2. Antibody ratios were measured by ELISA. KTX patients showed significantly lower SARS-CoV-2-specific IFN-γ responses after booster vaccination than healthy controls. However, SARS-CoV-2-specific IL-2 responses were comparable to the T cell responses of healthy controls. Cell culture-based neutralizing antibody titers were 1.3-fold higher in healthy controls for D614G, alpha, and delta, and 7.8-fold higher for omicron (p < 0.01). Healthy controls had approximately 2-fold higher concentrations of potential neutralizing antibodies against all 11 variants than KTX patients. However, more than 60% of the KTX patients displayed antibodies to variants of SARS-CoV-2. Thus, KTX patients should be partly protected, due to neutralizing antibodies to variants of SARS-CoV-2 or by cross-reactive T cells, especially those producing IL-2.

WO3 Photocatalyst Containing Copper Inactivates SARS-CoV-2 Pango Lineage A and Omicron BA.2 Variant in Visible Light and in Darkness

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019, which has been a global pandemic. Since SARS-CoV-2 is transmitted through contaminated surfaces and aerosols, environmental disinfection is important to block the spread of the virus. Photocatalysts are attractive tools for virus inactivation and are widely used as air purifiers and coating materials. However, photocatalysts are inactive in the dark, and some of them need to be excited with light of a specific wavelength. Therefore, photocatalysts that can effectively inactivate SARS-CoV-2 in indoor environments are needed. Here, we show that a WO3 photocatalyst containing copper inactivated the SARS-CoV-2 WK-521 strain (Pango lineage A) upon irradiation with white light in a time- and concentration-dependent manner. Additionally, this photocatalyst also inactivated SARS-CoV-2 in dark conditions due to the antiviral effect of copper. Furthermore, this photocatalyst inactivated not only the WK-521 strain but also the Omicron variant BA.2. These results indicate that the WO3 photocatalyst containing copper can inactivate indoor SARS-CoV-2 regardless of the variant, in visible light or darkness, making it an effective tool for controlling the spread of SARS-CoV-2.

Evaluation of Alternative Transport Media for RT-qPCR-Based SARS-CoV-2 Testing

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), is still rapidly spreading as of March 2022. An accurate and rapid molecular diagnosis is essential to determine the exact number of confirmed cases. Currently, the viral transport medium (VTM) required for testing is in short supply due to a sharp increase in the laboratory tests performed, and alternative VTMs are needed to alleviate the shortage. Guanidine thiocyanate-based media reportedly inactivate SARS-CoV-2 and are compatible with quantitative reverse transcription polymerase chain reaction (RT-qPCR) assays, but the compatibility and the viral detection capacity have not been fully validated. To evaluate the guanidine thiocyanate-based Gene Transport Medium (GeneTM) as an alternative VTM, we prepared 39 SARS-CoV-2-positive and 7 SARS-CoV-2-negative samples in GeneTM, eNAT™, and phosphate-buffered saline (PBS). The cycle threshold (Ct) values of three SARS-CoV-2 targets (the S, RdRP, and N genes) were analyzed using RT-qPCR testing. The comparison of Ct values from the positive samples showed a high correlation (R2= 0.95–0.96) between GeneTM and eNAT™, indicating a comparable viral detection capacity. The delta Ct values of the SARS-CoV-2 genes in each transport medium were maintained for 14 days at cold (4°C) or room (25°C) temperatures, suggesting viral samples were stably preserved in the transport media for 14 days. Together, GeneTM is a potential alternative VTM with comparable RT-qPCR performance and stability to those of standard media.

Effect of inactivating RNA viruses by coupled UVC and UVA LEDs evaluated by a viral surrogate commonly used as a genetic vector

RNA viruses are ubiquitous in nature, many of which can cause severe infectious syndromes to humanity, e.g., the SARS-CoV-2 virus. Ultraviolet (UV) radiation has been widely studied for inactivating various species of microorganisms, including viruses. The most applicable UV light for viruses ranges from 200nm to 280nm in wavelength, i.e., UVC. More recently, the synergy of UVA light with UVC has been studied in disinfecting bacteria in polluted water. However, little attention has been paid to studying viral inactivation by coupled UVC and UVA LEDs. The necessity of such research is to find an effective and economical solution for the LEDs of these two bands. Along this track, we attempt to tackle two major challenges. The first is to find a suitable viral surrogate that can safely be used in ordinary labs. In this aspect, lentivirus is commonly used as a genetic vector and has been selected to surrogate RNA viruses. Another is to determine the effective dosage of the coupled UVC and UVA light. To this end, the surrogate lentivirus was irradiated by 280nm (UVC) LEDs, 365nm (UVA) LEDs, and their combination at various doses. Survival rates were detected to compare the efficacy of various options. Moreover, the viral RNA damage was detected by RT-qPCR to disclose the mechanism of viral death. The results have shown that for the same duration of irradiation, the effect of the full-power 280nm LEDs is equivalent to that of the half-power 280nm LEDs combined with a suitable radiant power of the 365nm LEDs. The observations have been further confirmed by the effect of damaging the viral RNA by either the 280nm or 365nm light. In conclusion, the experimental results provide clear evidence of alleviating the requirement of UVC LEDs in viral inactivation by substituting them partially with UVA LEDs.

Review of concerned SARS-CoV-2 variants like Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529), as well as novel methods for reducing and inactivating SARS-CoV-2 mutants in wastewater treatment facilities

The coronavirus known as COVID-19, which causes pandemics, is causing a global epidemic at a critical stage today. Furthermore, novel mutations in the SARS-CoV-2 spike protein have been discovered in an entirely new strain, impacting the clinical and epidemiological features of COVID-19. Variants of these viruses can increase the transmission in wastewater, lead to reinfection, and reduce immunity provided by monoclonal antibodies and vaccinations. According to the research, a large quantity of viral RNA was discovered in wastewater, suggesting that wastewater can be a crucial source of epidemiological data and health hazards. The purpose of this paper is to introduce a few basic concepts regarding wastewater surveillance as a starting point for comprehending COVID-19's epidemiological aspects. Next, the observation of Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529) in wastewater is discussed in detail. Secondly, the essential information for the initial, primary, and final treating sewage in SARS-CoV-2 is introduced. Following that, a thorough examination is provided to highlight the newly developed methods for eradicating SARS-CoV-2 using a combination of solar water disinfection (SODIS) and ultraviolet radiation A (UVA (315-400 nm)), ultraviolet radiation B (UVB (280-315 nm)), and ultraviolet radiation C (UVC (100-280 nm)) processes. SARS-CoV-2 eradication requires high temperatures (above 56°C) and UVC. However, SODIS technologies are based on UVA and operate at cooler temperatures (less than 45°C). Hence, it is not appropriate for sewage treatment (or water consumption) to be conducted using SODIS methods in the current pandemic. Finally, SARS-CoV-2 may be discovered in sewage utilizing the wastewater-based epidemiology (WBE) monitoring method.

SARS-CoV-2 inactivation by ultraviolet radiation and visible light is dependent on wavelength and sample matrix

Numerous studies have demonstrated that SARS-CoV-2 can be inactivated by ultraviolet (UV) radiation. However, there are few data available on the relative efficacy of different wavelengths of UV radiation and visible light, which complicates assessments of UV decontamination interventions. The present study evaluated the effects of monochromatic radiation at 16 wavelengths from 222 nm through 488 nm on SARS-CoV-2 in liquid aliquots and dried droplets of water and simulated saliva. The data were used to generate a set of action spectra which quantify the susceptibility of SARS-CoV-2 to genome damage and inactivation across the tested wavelengths. UVC wavelengths (≤280 nm) were most effective for inactivating SARS-CoV-2, although inactivation rates were dependent on sample type. Results from this study suggest that UV radiation can effectively inactivate SARS-CoV-2 in liquids and dried droplets, and provide a foundation for understanding the factors which affect the efficacy of different wavelengths in real-world settings.

Immunogenic properties of SARS-CoV-2 inactivated by ultraviolet light

Vaccination against COVID-19 is the most effective method of controlling the spread of SARS-CoV-2 and reducing mortality from this disease. The development of vaccines with high protective activity against a wide range of SARS-CoV-2 antigenic variants remains relevant. In this regard, evaluation of the effectiveness of physical methods of virus inactivation, such as ultraviolet irradiation (UV) of the virus stock, remains relevant. This study demonstrates that the UV treatment of SARS-CoV-2 completely inactivates its infectivity while preserving its morphology, antigenic properties, and ability to induce the production of virus-neutralizing antibodies in mice through immunization. Thus, the UV inactivation of SARS-CoV-2 makes it possible to obtain viral material similar in its antigenic and immunogenic properties to the native antigen, which can be used both for the development of diagnostic test systems and for the development of an inactivated vaccine against COVID-19.

Sources, fates and treatment strategies of typical viruses in urban sewage collection/treatment systems: A review

The ongoing coronavirus pandemic (COVID-19) throughout the world has severely threatened the global economy and public health. Due to receiving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a wide variety of sources (e.g., households, hospitals, slaughterhouses), urban sewage treatment systems are regarded as an important path for the transmission of waterborne viruses. This review presents a quantitative profile of the concentration distribution of typical viruses within wastewater collection systems and evaluates the influence of different characteristics of sewer systems on virus species and concentration. Then, the efficiencies and mechanisms of virus removal in the units of wastewater treatment plants (WWTPs) are summarized and compared, among which the inactivation efficiencies of typical viruses by typical disinfection approaches under varied operational conditions are elucidated. Subsequently, the occurrence and removal of viruses in treated effluent reuse and desalination, as well as that in sewage sludge treatment, are discussed. Potential dissemination of viruses is emphasized by occurrence via aerosolization from toilets, the collection system and WWTP aeration, which might have a vital role in the transmission and spread of viruses. Finally, the frequency and concentration of viruses in reclaimed water, the probability of infection are also reviewed for discussing the potential health risks.

Ultrafast-UV laser integrating cavity device for inactivation of SARS-CoV-2 and other viruses

Ultraviolet (UV) irradiation-based methods used for viral inactivation have provided an important avenue targeting severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) virus. A major problem with state-of-the-art UV inactivation technology is that it is based on UV lamps, which have limited efficiency, require high power, large doses, and long irradiation times. These drawbacks limit the use of UV lamps in air filtering systems and other applications. To address these limitations, herein we report on the fabrication of a device comprising a pulsed nanosecond 266 nm UV laser coupled to an integrating cavity (LIC) composed of a UV reflective material, polytetrafluoroethylene. Previous UV lamp inactivation cavities were based on polished walls with specular reflections, but the diffuse reflective UV ICs were not thoroughly explored for virus inactivation. Our results show that LIC device can inactivate several respiratory viruses including SARS-CoV-2, at ~ 1 ms effective irradiation time, with > 2 orders of magnitude higher efficiency compared to UV lamps. The demonstrated 3 orders of magnitude cavity enhancement relative to direct exposure is crucial for the development of efficient real-time UV air and water purification systems. To the best of our knowledge this is the first demonstration of LIC application for broad viral inactivation with high efficiency.

UVC, UVB and UVA susceptibility of Phi6 and its suitability as a SARS-CoV-2 surrogate

For SARS-CoV-2 disinfection systems or applications that are based on UVC, UVB or UVA irradiation, it would be desirable to have a SARS-CoV-2 surrogate for tests and development, which does not require a laboratory with a high biosafety level. The bacteriophage Phi 6, an enveloped RNA virus like coronaviruses, is an obvious candidate for such a surrogate. In this study, UVC, UVB and UVA log-reduction doses for Phi6 are determined by plaque assay. Log-reduction doses for SARS-CoV-2 are retrieved from a literature research. Because of a high variability of the published results, median log-reduction doses are determined for defined spectral ranges and compared to Phi6 data in the same intervals. The measured Phi6 log-reduction doses for UVC (254 nm), UVB (311 nm) and UVA (365 nm) are 31.7, 980 and 14 684 mJ/cm2, respectively. The determined median log-reduction doses for SARS-CoV-2 are much lower, only about 1.7 mJ/cm2 within the spectral interval 251-270 nm. Therefore, Phi6 can be photoinactivated by all UV wavelengths but it is much less UV sensitive compared to SARS-CoV-2 in all UV spectral ranges. Thus, Phi6 is no convincing SARS-CoV-2 surrogate in UV applications.

Focused multivector ultraviolet (FMUV) technology rapidly eradicates SARS-CoV-2 in-vitro: Implications for hospital disinfection of COVID-19 environments

Focused Multivector Ultraviolet technology rapidly killed the SARS-CoV-2 coronavirus in-vitro. Plates were inoculated with a mean of greater than 10⁶ plaque forming units of USA-WA1 Washington index patient strain of SARS-CoV-2 and exposed to ultraviolet, resulting in mean reductions of 99.99% within 30 seconds, 99.999% within 60 seconds, and 99.9999% within 90 seconds. These results support the effectiveness of Focused Multivector Ultraviolet technology for SARS-CoV-2 disinfection.

Photocatalytic oxidation conveyor "PCOC" system for large scale surface disinfection

In this paper, we present a surface decontamination system that substitutes traditional chemicals and scrubbing agents, which will be useful for the general public during a pandemic. The technique is based on a hybrid process in which UV-C light and its photons interact with metal oxide nano-catalysts to generate hydroxyl radicals, which can enhance the deactivation process, and the system can work even in the shadow regions via a dry process. The optimum number of UV light sources in combination with TiO₂ nanoparticles catalysts on aluminum plates have been used synergistically in the system. The UV dose in the disinfection chamber has been optimized, which is between 60 and 500 mJ/cm² throughout the disinfection chamber. The concentration of hydroxyl radicals is reported more than 25 000 ions/cm³ within the disinfection chamber. These ions are circulated throughout the disinfection volume. The disinfection efficiency has been tested on bacteria and spores, and the obtained results are correlated. Around 8 log reductions in the counts of the test bacteria of Escherichia coli and Klebsiella pneumoniae have been achieved in just 2 min of exposure in the continuous operation of the system. Tests have also been performed on Geobacillus stearothermophilus spores, and the method described here is the result of multiple tests, a review of the scientific literature, and the incorporation of current laboratory practice. The deactivation tested in the system is larger than that of known bacteria and viruses in terms of UV-doses, signifying its utility during the pandemic.

Energy efficiency in large office buildings post-COVID-19 in Europe's top five economies

Since the World Health Organization announced the COVID-19 pandemic, indoor airflows became a synonym for virus super-spreaders and the focus point for the scientific community and professional associations across the globe, disrupting all daily life dimensions. Europe's quick response to control the disease led the REHVA board to address mitigation guidelines, reassessed by each member association's following national specifics. The present study aims to quantify the energy consumption and CO₂ emissions of "large office" buildings in top-five European economies under the COVID-19 guidelines under the post-pandemic telework forecast. Methodology resorted to a standard model under Building Energy Simulation assessment to compare prior and posterior scenarios. The latter displays a tendency to increase energy and CO₂ emissions in all locations, in the first form 10.18% (Rome) to 69.48% (Paris); and second 5.80% (Rome) and 120.61% (Paris), which will affect national energy production and imports, urban pollution and business competitiveness. On a different scope, future HVAC guidelines need to address the incoming figures, particularly in highly dense urban areas. Also, to comply with the goals set by the Paris Accord.

Metrological Traceability and Crucial Detector Characteristics for UVC Metrology in UVGI Applications

Ultraviolet-C (UVC) radiation-based sanitization has globally gained enormous importance in the current COVID-19 (caused by SARS-COV-2 virus) pandemic situation. The effectiveness of radiation sanitization is quantified in terms of ‘radiation dose’, which in turn is derived from a radiometric parameter ‘irradiance’, measured using UVC radiometer. Metrological traceability of irradiance/dose measurement is essentially required for achieving requisite accuracy of measurements, and hence germicidal efficacy. In the present article, the derivation of traceability for irradiance measurement using UVC radiometer is demonstrated. The critical conditions to be considered while using detector/radiometer for measuring UVC irradiance/dose in practical conditions are elaborated, avoiding which, significant errors in the UVC irradiance/dose may arise, and hence, may compromise the performance of the Ultraviolet Germicidal Irradiation (UVGI) devices.

UV and violet light can Neutralize SARS-CoV-2 Infectivity

We performed an in-depth analysis of the virucidal effect of discrete wavelengths: UV-C (278 nm), UV-B (308 nm), UV-A (366 nm) and violet (405 nm) on SARS-CoV-2. By using a highly infectious titer of SARS-CoV-2 we observed that the violet light-dose resulting in a 2-log viral inactivation is only 104 times less efficient than UV-C light. Moreover, by qPCR (quantitative Polymerase chain reaction) and fluorescence in situ hybridization (FISH) approach we verified that the viral titer typically found in the sputum of COVID-19 patients can be completely inactivated by the long UV-wavelengths corresponding to UV-A and UV-B solar irradiation. The comparison of the UV action spectrum on SARS-CoV-2 to previous results obtained on other pathogens suggests that RNA viruses might be particularly sensitive to long UV wavelengths. Our data extend previous results showing that SARS-CoV-2 is highly susceptible to UV light and offer an explanation to the reduced incidence of SARS-CoV-2 infection seen in the summer season.

DUV coherent light emission from ultracompact microcavity wavelength conversion device

A unique design of our ultracompact microcavity wavelength conversion device exploits the simple principle that the wavelength conversion efficiency is proportional to the square of the electric field amplitude of enhanced pump light in the microcavity, and expands the range of suitable device materials to include crystals that do not exhibit birefringence or ferroelectricity. Here, as a first step toward practical applications of all-solid-state ultracompact deep-ultraviolet coherent light sources, we adopted a low-birefringence paraelectric SrB₄O₇ crystal with great potential for wavelength conversion and high transparency down to 130 nm as our device material, and demonstrated 234 nm deep-ultraviolet coherent light generation, whose wavelength band is expected to be used for on-demand disinfection tools that can irradiate the human body.

Instant inactivation of aerosolized SARS-CoV-2 by dielectric filter discharge

This study aimed to evaluate the instant inactivation effect of dielectric filter discharge (DFD) on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) aerosols. The filter consisted of one layer of ZrO2 beads covered by aluminum mesh electrodes; this porous structure of DFD part generates filter-type surface discharge and reactive oxygen species. In a closed cylindrical chamber, DFD treated air flow containing SARS-CoV-2 aerosols, primarily composed of particle diameters of ≤ 1 μm. A polypropylene melt-blown filter collected the treated bioaerosols for inactivation analysis. Plaque and polymerase chain reaction assays showed that the aerosolized SARS-CoV-2 that passed through the filter were more than 99.84% inactivated with degradation of SARS-CoV-2 genes (ORF1ab and E). However, ozone exposure without DFD passage was not found to be effective for bioaerosol inactivation in plaque assay.

Efficient disinfection of SARS-CoV-2-like coronavirus, pseudotyped SARS-CoV-2 and other coronaviruses using cold plasma induces spike protein damage

Coronavirus disease 2019 (COVID-19) has become a worldwide public health emergency, and the high transmission of SARS-CoV-2 variants has raised serious concerns. Efficient disinfection methods are crucial for the prevention of viral transmission. Herein, pulse power-driven cold atmospheric plasma (CAP), a novel sterilization strategy, was found to potently inactivate SARS-CoV-2-like coronavirus GX_P2V, six strains of major epidemic SARS-CoV-2 variants and even swine coronavirus PEDV and SADS-CoV within 300 s (with inhibition rate more than 99%). We identified four dominant short-lived reactive species, ONOO^-, ¹O₂, O₂^- and·OH, generated in response to CAP and distinguished their roles in the inactivation of GX_P2V and SARS-CoV-2 spike protein receptor binding domain (RBD), which is responsible for recognition and binding to human angiotensin-converting enzyme 2 (hACE2). Our study provides detailed evidence of a novel surface disinfection strategy for SARS-CoV-2 and other coronaviruses.

Reduction and discharge of SARS-CoV-2 RNA in Chicago-area water reclamation plants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA is commonly excreted in the feces and urine of infected individuals and is, therefore, detected in wastewaters where infection is present in the surrounding population. Water reclamation plants (WRPs) that treat these wastewaters commonly discharge treated effluents into the surrounding environment, yet little is known about the removal or persistence of SARS-CoV-2 RNA through wastewater treatment systems and potential for eventual release into the environment. We collected 361 24-hour composite influent and effluent samples from seven WRPs in the Greater Chicago Area in Illinois. Samples were collected over a period of 21 weeks for three large WRPs (with design max flows of 1.89-2.32 billion gallons per day and serving a combined population of 4.62 million people) and 11 weeks for four smaller WRPs (with design max flows of 96.3-186 million gallons per day and serving a combined population of >0.5 million people). A total of two of the larger WRPs implemented seasonal disinfection (using UV light or chlorination/dechlorination) for 8 weeks of this sampling period. SARS-CoV-2 RNA was quantified in the influent and effluent samples by reverse-transcription quantitative PCR (RT-qPCR) of the N1 and N2 targets of the nucleocapsid (N) gene. Although SARS-CoV-2 RNA was regularly detected in influent and effluent from all WRPs, viral RNA concentrations in the effluent samples were considerably lower, with mean effluent: influent gene copy concentration ratios ranging from 1:160 to 1:2.95 between WRPs. Samples collected while disinfection was active vs. inactive did not show any significant difference in the portion of RNA persisting through the treatment process (P > .05).

Comparative investigation of toxicity induced by UV-A and UV-C radiation using Allium test

Organisms are increasingly exposed to ultraviolet (UV) rays of sunlight, due to the thinning of the ozone layer and its widespread use in sterilization processes, especially against the SARS-CoV-2 virus. The present study was conducted with the purpose of evaluating the damages of UV-A and UV-C radiations in Allium cepa L. roots. The effects of two different types of UV on some physiological, biochemical, cytogenotoxic, and anatomical parameters were investigated in a multifaceted study. Three groups were formed from Allium bulbs, one of which was the control group. One of the other groups was exposed to 254 nm (UV-C) and the other to 365 nm (UV-A) UV. Growth retardation effect of UV was investigated with respect to germination percentage, total weight gain, and root elongation, while cytogenotoxicity arisen from UV exposure was analyzed using mitotic index (MI) and chromosomal aberration (CA) and micronucleus (MN) frequency. Oxidative stress due to UV application was investigated based on the accumulation of malondialdehyde (MDA) and the total activities of superoxide dismutase (SOD) and catalase (CAT) enzymes. Also, anatomical changes induced by UV-A and UV-C were analyzed in root meristematic cells. UV treatments caused significant reductions in growth-related parameters. Both UV treatments caused a significant increase in MDA levels and induction of SOD and CAT enzymes in root meristematic cells. A decrease in MI and an increase in the frequency of MN and CAs were observed in root tip cells, indicating the cytogenotoxic effect of UV application. Anatomical damages such as epidermis cell damage, cortex cell damage, necrotic zones, giant cell nucleus, and indistinct transmission tissue occurred in cells exposed to UV. All of the physiological, biochemical, cytogenetic, and anatomical damages observed in this study were more severe in cells treated with UV-C compared to UV-A. This study suggested that UV exposure triggered growth inhibition, cytogenotoxicity, oxidative stress, and meristematic cell damages in A. cepa roots depending on the wavelength.

A 265-Nanometer High-Power Deep-UV Light-Emitting Diode Rapidly Inactivates SARS-CoV-2 Aerosols

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (COVID-19) is an acute respiratory infection transmitted by droplets, aerosols, and contact. Controlling the spread of COVID-19 and developing effective decontamination options are urgent issues for the international community. Here, we report the quantitative inactivation of SARS-CoV-2 in liquid and aerosolized samples by a state-of-the-art, high-power, AlGaN-based, single-chip compact deep-UV (DUV) light-emitting diode (LED) that produces a record continuous-wave output power of 500 mW at its peak emission wavelength of 265 nm. Using this DUV-LED, we observed a greater-than-5-log reduction in infectious SARS-CoV-2 in liquid samples within very short irradiation times (<0.4 s). When we quantified the efficacy of the 265-nm DUV-LED in inactivating SARS-CoV-2, we found that DUV-LED inactivation of aerosolized SARS-CoV-2 was approximately nine times greater than that of SARS-CoV-2 suspension. Our data demonstrate that this newly developed, compact, high-power 265-nm DUV-LED irradiation system with remarkably high inactivation efficiency for aerosolized SARS-CoV-2 could be an effective and practical tool for controlling SARS-CoV-2 spread. IMPORTANCE We developed a 265-nm high-power DUV-LED irradiation system and quantitatively demonstrated that the DUV-LED can inactivate SARS-CoV-2 in suspensions and aerosols within very short irradiation times. We also found that the inactivation effect was about nine times greater against aerosolized SARS-CoV-2 than against SARS-CoV-2 suspensions. The DUV-LED has several advantages over conventional LEDs and mercury lamps, including high power, compactness, and environmental friendliness; its rapid inactivation of aerosolized SARS-CoV-2 opens up new possibilities for the practical application of DUV-LEDs in high-efficiency air purification systems to control airborne transmission of SARS-CoV-2.

Investigation of mouse hepatitis virus strain A59 inactivation under both ambient and cold environments reveals the mechanisms of infectivity reduction following UVC exposure

The surface contamination of SARS-CoV-2 is becoming a potential source of virus transmission during the pandemic of COVID-19. Under the cold environment, the infection incidents would be more severe with the increase of virus survival time. Thus, the disinfection of contaminated surfaces in both ambient and cold environments is a critical measure to restrain the spread of the virus. In our study, it was demonstrated that the 254 nm ultraviolet-C (UVC) is an efficient method to inactivate a coronavirus, mouse hepatitis virus strain A59 (MHV-A59). The inactivation rate to MHV-A59 coronavirus was up to 99.99% when UVC doses were 2.90 and 14.0 mJ/cm² at room temperature (23 °C) and in cold environment (-20 °C), respectively. Further mechanistic study demonstrated that UVC could induce spike protein damage to partly impede virus attachment and genome penetration processes, which contributes to 12% loss of viral infectivity. Additionally, it can induce genome damage to significantly interrupt genome replication, protein synthesis, virus assembly and release processes, which takes up 88% contribution to viral inactivation. With these mechanistic understandings, it will greatly contribute to the prevention and control of the current SARS-CoV-2 transmissions in cold chains (low temperature-controlled product supply chains), public area such as airport, school, and warehouse.

Effective ultraviolet C light disinfection of respirators demonstrated in challenges with Geobacillus stearothermophilus spores and SARS-CoV-2 virus

BACKGROUND

The global COVID-19 pandemic, accompanied by spikes in the number of patients in hospitals, required substantial amounts of respiratory protective devices (respirators), thereby causing shortages. Disinfection of used respirators by applying ultraviolet C (UVC) light may enable safe reuse, reducing shortages.

AIM

To determine whether UVC disinfection is applicable to enable repeated safe reuse of respirators.

METHODS

The UVC chamber, equipped with low-pressure mercury discharge lamps emitting at 254 nm, was used to determine the sporicidal and virucidal effects. Respirators challenged with spores and viruses were exposed to various UVC energy levels. Deactivation of the biological agents was studied as well as UVC effects on particle filtration properties and respirator fit.

FINDINGS

A 5 log10 reduction of G. thermophilus spore viability by a UVC dose of 1.1 J/cm2 was observed. By simulating spores present in the middle of the respirators, a 5 log10 reduction was achieved at a UVC dose of 10 J/cm2. SARS-CoV-2 viruses were inactivated by 4 log10 upon exposure to 19.5 mJ/cm2 UVC. In case UVC must be transmitted through all layers of the respirators to reach the spores and virus, a reduction of >5 log10 was achieved using a UVC dose of 10 J/cm2. Exposure to a six-times higher UVC dose did not significantly affect the integrity of the fit nor aerosol filtering capacity of the respirator.

CONCLUSION

UVC was shown to be a mild and effective way of respirator disinfection allowing for reuse of the UVC-treated respirators.

UVC-PURGE: A Novel Cost-Effective Disinfection Robot for Combating COVID-19 Pandemic

During the COVID-19 pandemic, surface disinfection using prevailing chemical disinfection methods had several limitations. Due to cost-inefficiency and the inability to disinfect shaded places, static UVC lamps cannot address these limitations properly. Moreover, the average market price of the prevailing UVC robots is huge, approximately 55,165 USD. In this research firstly, a requirement elicitation study was conducted using a semi-structured interview approach to reveal the requirements to develop a cost-effective UVC robot. Secondly, a semi-autonomous robot named UVC-PURGE was developed based on the revealed requirements. Thirdly, a two-phased evaluation study was undertaken to validate the effectiveness of UVC-PURGE to inactivate the SARS-CoV-2 virus and the capability of semi-autonomous navigation in the first phase and to evaluate the usability of the system through a hybrid approach of SUPR-Q forms and subjective evaluation of the user feedback in the second phase. Pre-treatment swab testing revealed the presence of both Gram-positive and Gram-Negative bacteria at 17 out of 20 test surfaces in the conducted tests. After the UVC irradiation of the robot, the microbial load was detected in only 2 (1D and 1H) out of 17 test surfaces with significant reductions (95.33% in 1D and 90.9% in 1H) of microbial load. Moreover, the usability evaluation yields an above-average SUPR-Q score of 81.91% with significant scores in all the criteria (usability, trust, loyalty, and appearance) and the number of positive themes from the subjective evaluation using thematic analysis is twice the number of negative themes. Additionally, compared with the prevailing UVC disinfection robots in the market, UVC-PURGE is cost-effective with a price of less than 800 USD. Moreover, small form factor along with the real time camera feedback in the developed system helps the user to navigate in congested places easily. The developed robot can be used in any indoor environment in this prevailing pandemic situation and it can also provide cost-effective disinfection in medical facilities against the long-term residual effect of COVID-19 in the post-pandemic era.

Effect of Ultraviolet Light C (UV-C) Radiation Generated by Semiconductor Light Sources on Human Beta-Coronaviruses' Inactivation

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has completely disrupted people’s lives. All over the world, many restrictions and precautions have been introduced to reduce the spread of coronavirus disease 2019 (COVID-19). Ultraviolet C (UV-C) radiation is widely used to disinfect rooms, surfaces, and medical tools; however, this paper presents novel results obtained for modern UV-C light-emitting diodes (LEDs), examining their effect on inhibiting the multiplication of viruses. The main goal of the work was to investigate how to most effectively use UV-C LEDs to inactivate viruses. We showed that UV-C radiation operating at a 275 nm wavelength is optimal for germicidal effectiveness in a time exposure (25−48 s) study: >3 log-reduction with the Kärber method and >6 log-reduction with UV spectrophotometry were noted. We used real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) to reliably estimate virus infectivity reduction after 275 nm UV-C disinfection. The relative quantification (RQ) of infectious particles detected after 40−48 s distinctly decreased. The irradiated viral RNAs were underexpressed compared to the untreated control virial amplicon (estimated as RQ = 1). In conclusion, this work provides the first experimental data on 275 nm UV-C in the inactivation of human coronavirus OC43 (HoV-OC43), showing the most potent germicidal effect without hazardous effect.

UV-C Light-Based Surface Disinfection: Analysis of Its Virucidal Efficacy Using a Bacteriophage Model

Background: The reprocessing of medical devices has become more complex due to increasing hygiene requirements. Previous studies showed satisfactory bactericidal disinfection effects of UV-C light in rigid and flexible endoscopes. Especially in the context of the current COVID-19 pandemic, virucidal properties are of high importance. In the present study, the virucidal efficacy of UV-C light surface disinfection was analyzed. Methods: MS-2 bacteriophages were applied to the test samples and irradiated by UV-C light using the UV Smart D25 device; unirradiated test samples were used as controls. A dilution series of the samples was mixed with 1 × 108 Escherichia coli and assayed. Results: 8.6 × 1012 pfu could be harvested from the unprocessed test samples. In the control group without UV-C exposure, a remaining contamination of 1.2 × 1012 pfu was detected, resulting in a procedural baseline reduction rate with a LOG10 reduction factor of 0.72. The LOG10 reduction factor was found to be 3.0 after 25 s of UV-C light exposure. After 50 and 75 s of UV-C radiation LOG10 reduction factors 4.2 and 5.9, respectively, were found, with all reductions being statistically significantly different to baseline. Conclusions: The tested UV system seems to provide a significant virucidal effect after a relatively short irradiation time.

Evaluation of UV-C Radiation Efficiency in the Decontamination of Inanimate Surfaces and Personal Protective Equipment Contaminated with Phage ϕ6

To help halt the global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), appropriate disinfection techniques are required. Over the last years, the interest in Ultraviolet-C (UV-C) radiation as a method to disinfect inanimate surfaces and personal protective equipment (PPE) has increased, mainly to efficiently disinfect and prevent SARS-CoV-2 from spreading and allow for the safe reuse of said equipment. The bacteriophage ϕ6 (or simply phage ϕ6) is an RNA virus with a phospholipid envelope and is commonly used in environmental studies as a surrogate for human RNA-enveloped viruses, including SARS-CoV-2. The present study investigated the use of two new UV irradiation systems ((2)2.4W and (8)5.5W)) constituted by conventional mercury UV-C lamps with a strong emission peak at ~254 nm to potentially inactivate phage ϕ6 on different surfaces (glass, plastic, stainless steel, and wood) and personal protective equipment, PPE, (surgical and filtering facepiece 2, FFP2, masks, a clear acetate visor, and disposable protective clothing). The results showed that both UV-C systems were effective in inactivating phage ϕ6, but the UV-C sterilizing chamber (8)5.5W had the best disinfection performance on the tested surfaces. The inactivation effectiveness is material-dependent on all surfaces, reaching the detection limit of the method at different times (between 60 and 240 s of irradiation). The glass surface needed less time to reduce the virus (30 s) when compared with plastic, stainless, and wood surfaces (60 s). The virus inactivation was more effective in the disposable surgical and FFP2 masks (60 and 120 s, respectively) than in the disposable vest and clear acetate visor (240 s). Overall, this study suggests that UV-C lamps with peak emission at ~254 nm could provide rapid, efficient, and sustainable sanitization procedures to different materials and surfaces. However, dosage and irradiation time are important parameters to be considered during their implementation as a tool in the fight against human coronaviruses, namely against SARS-CoV-2.

A Methodology for Remote Microwave Sterilization Applicable to the Coronavirus and Other Pathogens Using Retrodirective Antenna Arrays

This paper describes an innovative remote surface sterilization approach applicable to the new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The process is based on the application of a liquid film on the surface or object under sterilization (OUS). A beacon signal is used to self-steer the transmitted power from the designed retrodirective antenna array (RDA) towards the OUS using circularly polarized fields; then, the sterilization is completed by raising and maintaining the required temperature for a certain time. Results suggest that the process takes 5 minutes or less for an angular coverage range over 60 degrees whilst abiding by the relevant safety protocols. This paper also models the power incident onto the OUS, providing consistent results with full-wave simulations. A practical RDA system is developed using a 2 × 1 microstrip patch array operating at 2.5 GHz and tested through the positioning of a representative target surface. Measurements, developed by sampling the power transmitted by the heterodyne RDA, are reported for various distances and angles, operating in the near-field of the system. To further validate the methodology, an additional experiment investigating virus deactivation through microwave heating was also developed. Measurements have been performed with an open cavity microwave oven on the Coronavirus (strain 229E) and egg white protein in a cuvette. This demonstrates that the temperature increases of aqueous films up to 70 [Formula: see text]C by remote microwave-induced heat can denature proteins and deactivate viruses. Possible applications of the method include sterilization of ambulances, medical equipment, and internet of things (IoT) devices.

SARS-CoV-2 aerosol transmission and detection

Aerosol transmission has been officially recognized by the world health authority resulting from its overwhelming experimental and epidemiological evidences. Despite substantial progress, few additional actions were taken to prevent aerosol transmission, and many key scientific questions still await urgent investigations. The grand challenge, the effective control of aerosol transmission of COVID-19, remains unsolved. A better understanding of the viral shedding into the air has been developed, but its temporal pattern is largely unknown. Sampling tools, as one of the critical elements for studying SARS-CoV-2 aerosol, are not readily available around the world. Many of them are less capable of preserving the viability of SARS-CoV-2, thus offering no clues about viral aerosol infectivity. As evidenced, the viability of SARS-CoV-2 is also directly impacted by temperature, humidity, sunlight, and air pollutants. For SARS-CoV-2 aerosol detection, liquid samplers, together with real-time polymerase chain reaction (RT-PCR), are currently used in certain enclosed or semi-enclosed environments. Sensitive and rapid COVID-19 screening technologies are in great need. Among others, the breath-borne-based method emerges with global attention due to its advantages in sample collection and early disease detection. To collectively confront these challenges, scientists from different fields around the world need to fight together for the welfare of mankind. This review summarized the current understanding of the aerosol transmission of SARS-CoV-2 and identified the key knowledge gaps with a to-do list. This review also serves as a call for efforts to develop technologies to better protect the people in a forthcoming reopening world.

Optimization algorithms as training approach with hybrid deep learning methods to develop an ultraviolet index forecasting model

The solar ultraviolet index (UVI) is a key public health indicator to mitigate the ultraviolet-exposure related diseases. This study aimed to develop and compare the performances of different hybridised deep learning approaches with a convolutional neural network and long short-term memory referred to as CLSTM to forecast the daily UVI of Perth station, Western Australia. A complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) is incorporated coupled with four feature selection algorithms (i.e., genetic algorithm (GA), ant colony optimization (ACO), particle swarm optimization (PSO), and differential evolution (DEV)) to understand the diverse combinations of the predictor variables acquired from three distinct datasets (i.e., satellite data, ground-based SILO data, and synoptic mode climate indices). The CEEMDAN-CLSTM model coupled with GA appeared to be an accurate forecasting system in capturing the UVI. Compared to the counterpart benchmark models, the results demonstrated the excellent forecasting capability (i.e., low error and high efficiency) of the recommended hybrid CEEMDAN-CLSTM model in apprehending the complex and non-linear relationships between predictor variables and the daily UVI. The study inference can considerably enhance real-time exposure advice for the public and help mitigate the potential for solar UV-exposure-related diseases such as melanoma.