INTRODUCTION:The spread of Candida auris (C. auris), methicillin-resistant Staphylococcus aureus (MRSA) and various viruses in healthcare settings is of global concern. Far-UV-C222 reduces the concentration of microorganisms in laboratory settings and can be used directly in patient care rooms at doses safe for human eyes and skin. The effectiveness of UV-C222 inactivation of C. auris, MRSA and T1 bacteriophage (a viral surrogate) in a hospital setting was studied. METHODS:A partially blinded, cross-over study was conducted of two conditions: intervention, active UV and control, no UV. C. auris, MRSA and T1 bacteriophage were inoculated and dried onto stainless steel disc carriers at two soil levels, (0.03% BSA and 5.0% CBS), and placed at 24 locations in two unoccupied, two-bed patient rooms. UV-C222 luminaires were placed behind the head of each bed and one in the bathroom for both study rooms. Simultaneous 24-h exposures for both rooms were in random order. Pathogens were processed for cultures. RESULTS:UV-C222 doses exposing the discs ranged from a low of 5 mJ/cm2 to high 637 mJ/cm2. Under treatment conditions, MRSA showed a 1.0 log reduction in 0.03% soil, C. auris showed a 2.6 log reduction in 0.03% soil and a 1.0 log reduction in 5.0% soil and T1 bacteriophage showed a 0.6 log reduction in 0.03% soil. CONCLUSIONS:In patient rooms, continuous UV-C222 exposure showed decreased concentrations of C. auris (low and high soil), MRSA (low soil), and T1 (low soil). Studies are needed to determine benefits in occupied settings.

The UV inactivation rate constant (k-value) is a critical parameter for designing germicidal UV (GUV) systems. However, significant variability in reported k-values in the literature creates uncertainty. We conducted a comprehensive literature review of 360 papers and determined design k-values for seven important pathogenic microorganisms: Influenza virus, Human coronavirus, Adenovirus, Staphylococcus, Clostridioides difficile, Mycobacterium tuberculosis, and Measles virus, and three common surrogates: E. coli, MS2, and Bacillus subtilis. The review examines the effects of wavelength (200-280 nm), GUV light source (LMPV and UVC-LED, and KrCl-excimer), and environmental conditions on k-values across different media, including air, surfaces, suspensions, water, and wastewater. We propose design k-values (mean +/- standard deviations) based on available data. For 254-nm UVC in air, the recommended k-values are: Influenza virus (0.26 +/- 0.029 m2/J), Adenovirus (0.053 +/- 0.012 m2/J), Mycobacterium tuberculosis (0.41 +/- 0.075 m2/J), E. coli (0.48 +/- 0.25 m2/J), and MS2 (0.30 +/- 0.28 m2/J). For 254-nm UVC on surfaces, the recommended k-values are: Human coronavirus (0.060 +/- 0.057 m2/J), Staphylococcus (0.053 +/- 0.050 m2/J), and Clostridioides difficile (0.032 +/- 0.030 m2/J). This parameter for Bacillus subtilis on surfaces at 248-nm is 0.0017 +/- 0.00096 m2/J and for Measles virus suspended on agar plates at 254-nm is 0.084 m2/J. We also identified an urgent need for standardizing testing, analysis, and reporting of k-value.

Poor sleep is common in hospitalised patients due to multiple factors, including disruption of the circadian rhythm. Few studies have examined programmable artificial lighting systems in hospital patient rooms, and few have achieved meaningful improvement in sleep. We sought to determine how novel dynamic lighting affects sleep timing and duration compared to standard hospital lighting. Patients were admitted to rooms on a cardiology unit with customised intervention or standard lighting. The lighting system delivered blue-enriched light during the day, a melanopic stimulus twice daily and blue-depleted light in the evening. Sleep/wake probability was measured in 30-s epochs using mattress sensors to capture sleep timing and nocturnal sleep duration. Subjective sleep duration and alertness were assessed with sleep diaries and the Karolinska Sleepiness Scale (KSS), respectively. A total of 87 patients were enrolled. Subjects experiencing customised lighting demonstrated significantly advanced rest/wake activity phase by 160 min and overall greater sleep probability. Overnight sleep duration (11 p.m.-7 a.m.) was 66 min greater in the lighting condition (266 vs. 200 min, p < 0.05). Patients in the intervention group reported higher levels of alertness during the morning (KSS score 3.8 vs. 4.9, p = 0.01) and evening (5.4 vs. 7.1, p = 0.01). A lighting system programmed to entrain the circadian rhythm and provide a daytime melanopic stimulus on a hospital unit was associated with advanced circadian phase, increased nocturnal sleep duration and increased perceived morning and evening alertness. These results suggest that dynamic lighting systems have the potential to improve sleep for hospitalised patients.

Respiratory interventions including noninvasive ventilation, continuous positive airway pressure and high-flow nasal oxygen generated infectious aerosols may increase risk of airborne disease (SARS-CoV-2, influenza virus) transmission to healthcare workers. We developed and tested a prototype portable UV-C254 device to sterilize high flows of viral-contaminated air from a simulated patient source at airflow rates of up to 100 l/m. Our device consisted of a central quartz tube surrounded 6 high-output UV-C254 lamps, within a larger cylinder allowing recirculation past the UV-C254 lamps a second time before exiting the device. Testing was with nebulized A/PR/8/34 (H1N1) influenza virus. RNA extraction and qRT-PCR showed virus transited through the prototype. Turning on varying numbers of lamps controlled the dose of UVC. Viability experiments at low, medium and high (100 l/min) flows of contaminated gas were conducted with 6, 4, 2 and 1 lamp activated (single-pass and recirculation were tested). Our data show 5-log reduction in plaque forming units from a single lamp (single- pass and recirculated conditions) at high and low flows. UVC dose at 100 l/m was calculated at 11.6 mJ/cm2 single pass and 104 mJ/cm2 recirculated. The protype device shows high efficacy in killing nebulized influenza virus in a high flow of contaminated air.

BACKGROUND:Healthcare workers (HWs) are at a high risk of exposure to emerging health threats. Following the first wave of the coronavirus disease 2019 pandemic in Cameroon, we explored the presence and persistence of naturally acquired antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the factors associated with seropositivity in HWs. METHODS:Staff at two referral hospitals in Yaoundé or two Health District Hospitals in Obala and Mbalmayo were included in a 6-month prospective cohort analysis or cross-sectional survey, respectively. Seroprevalence and associated factors were determined, and Kaplan-Meier curves and Cox proportional hazards models were used to assess antibody persistence or positive seroconversion over time. RESULTS:From August 2020 to March 2021, 426 HWs (median age: 31 years, interquartile range: 27-37 years; 66.4% female) were enrolled. The overall seroprevalence of anti-SARS-CoV-2 antibodies was 54.0% (95% confidence interval [CI]: 49.1-58.8) and was significantly different between study sites (p = 0.04). Of the 216 HWs included in the 6-month cohort, 109 (50.5%) HWs were seropositive at inclusion; the probability of persistent antibodies or of becoming seropositive was 93.8% (95% CI: 84.2-100) and 78.9% (95% CI: 61.7-88.4), respectively. Seroconversion was associated with study site and occupation but not with infection prevention and control (IPC) practices. CONCLUSIONS:We observed high seroprevalence of SARS-CoV-2 antibody and seroconversion among HWs associated with occupational risk. This suggests low compliance to the COVID-19 control measures. Continued training and implementation of IPC measures and accelerated preparedness are needed to better tackle future threats.

This study used Computational Fluid Dynamics (CFD) to investigate air disinfection for SARS-CoV-2 by the Upper-Room Germicidal Ultraviolet (UR-GUV), with focus on ceiling impact. The study includes three indoor settings, i.e., low (airport bus), medium (classroom) and high (rehearsal room) ceilings, which were ventilated with 100% clean air (CA case), 80% air-recirculation with a low filtration (LF case), and 80% air-recirculation with a high filtration (HF case). According to the results, using UR-GUV can offset the increased infection risk caused by air recirculation, with viral concentrations in near field (NF) and far field (FF) in the LF case similar to those in the CA case. In the CA case, fraction remaining (FR) was 0.48-0.73 with 25% occupancy rate (OR) and 0.49-0.91 with 45% OR in the bus, 0.41 in NF and 0.11 in FF in the classroom, and 0.18 in NF and 0.09 in FF in the rehearsal room. Obviously, UR-GUV performance in NF can be improved in a room with a high ceiling where FR has a power relationship with UV zone height. As using UR-GUV can only extend the exposure time to get infection risk of 1% (T1%) to 8 min in NF in the classroom, and 47 min in NF in the rehearsal room, it is necessary to abide by social distancing in the two rooms. In addition, T1% in FF was calculated to be 18.3 min with 25% OR and 21.4% with 45% OR in the airport bus, showing the necessity to further wear a mask.

Particulate respirators such as N95s are an essential component of personal protective equipment (PPE) for front-line workers. This study describes a rapid and effective UVC irradiation system that would facilitate the safe re-use of N95 respirators and provides supporting information for deploying UVC for decontamination of SARS-CoV-2 during the COVID-19 pandemic. To assess the inactivation potential of the proposed UVC germicidal device as a function of time by using 3 M 8211-N95 particulate respirators inoculated with SARS-CoV-2. A germicidal UVC device to deliver tailored UVC dose was developed and test coupons (2.5 cm 2 ) of the 3 M-N95 respirator were inoculated with 10 6 plaque-forming units (PFU) of SARS-CoV-2 and were UV irradiated. Different exposure times were tested (0–164 s) by fixing the distance between the lamp and the test coupon to 15.2 cm while providing an exposure of at least 5.43 mWcm −2 . Primary measure of outcome was titration of infectious virus recovered from virus-inoculated respirator test coupons after UVC exposure. Other measures included the method validation of the irradiation protocol, using lentiviruses (biosafety level-2 agent) and establishment of the germicidal UVC exposure protocol. An average of 4.38 × 10 3 PFU ml −1 (SD 772.68) was recovered from untreated test coupons while 4.44 × 10 2 PFU ml −1 (SD 203.67), 4.00 × 10 2 PFU ml −1 (SD 115.47), 1.56 × 10 2 PFU ml −1 (SD 76.98) and 4.44 × 10 1 PFU ml −1 (SD 76.98) was recovered in exposures 2, 6, 18 and 54 s per side respectively. The germicidal device output and positioning was monitored and a minimum output of 5.43 mW cm −2 was maintained. Infectious SARS-CoV-2 was not detected by plaque assays (minimal level of detection is 67 PFU ml −1 ) on N95 respirator test coupons when irradiated for 120 s per side or longer suggesting 3.5 log reduction in 240 s of irradiation, 1.3 J cm −2 . A scalable germicidal UVC device to deliver tailored UVC dose for rapid decontamination of SARS-CoV-2 was developed. UVC germicidal irradiation of N95 test coupons inoculated with SARS-CoV-2 for 120 s per side resulted in 3.5 log reduction of virus. These data support the reuse of N95 particle-filtrate apparatus upon irradiation with UVC and supports use of UVC-based decontamination of SARS-CoV-2 during the COVID-19 pandemic.

Mobile whole‐room UVGI devices are used in healthcare settings to control surface‐borne pathogens. Unfortunately, no standard method comparing the efficacy of these devices is available. We accessed the effect of shadows on UVC 254 nm inactivation. The evaluation of a mobile whole‐room UVGI device used spores of Bacillus atrophaeus as a surrogate for Clostridium difficile and Staphylococcus aureus as a surrogate for MSRA. Inactivation after 10 min of exposure varied significantly depending on whether the spores received direct UV exposure (4.3 log reduction), both direct and reflected UV exposure (3.0–4.0 log reduction) or reflected UV exposure alone (<1.0 log reduction). The susceptibility ( z ‐value) for inactivation of B. atrophaeus spores on a glass surface was estimated to be 0.00312 m 2 J −1 . Staphylococcus aureus microbial log reductions were approximately 5.5 for direct UV exposure, 3.6–5.2 for both direct and reflected UV exposure and approximately 2.75 for only reflected UV exposure. Our measurement of reflected dose ranged from 0.46% to 1.47%. Based on our findings, B. atrophaeus spores should be considered as a model organism for testing the impact of shadows on mobile whole‐room UVGI device inactivation. Optimizing the reflected component of whole‐room UVGI is important, especially for UVC‐resistant organisms.

Photochemistry and PhotobiologyVolume 97, Issue 3 p. 464-465 EditorialOpen Access Air Disinfection with Germicidal Ultraviolet: For this Pandemic and the Next Rolf Bergman, Rolf Bergman Rolf Bergman Consulting, Cleveland, OHSearch for more papers by this authorDavid Brenner, David Brenner Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorManuela Buonanno, Manuela Buonanno orcid.org/0000-0002-3455-3602 Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorEwan Eadie, Ewan Eadie orcid.org/0000-0002-7824-5580 Photobiology Unit, NHS Tayside, Ninewells Hospital and Medical School, Dundee, UKSearch for more papers by this authorPaul Donald Forbes, Paul Donald Forbes orcid.org/0000-0003-4521-8495 Toxarus, Inc., Malvern, PASearch for more papers by this authorPaul Jensen, Paul Jensen orcid.org/0000-0001-7367-4952 Final Approach Inc., Port Orange, FLSearch for more papers by this authorEdward A. Nardell, Edward A. Nardell orcid.org/0000-0002-5323-3196 Harvard Medical School, Harvard School of Public Health, Boston, MASearch for more papers by this authorDavid Sliney, Corresponding Author David Sliney david.sliney@att.net orcid.org/0000-0003-4859-5982 Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MDSearch for more papers by this authorRichard Vincent, Richard Vincent orcid.org/0000-0003-3453-4070 General Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, NYSearch for more papers by this authorDavid Welch, David Welch Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorKenneth Wood, Kenneth Wood SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, UKSearch for more papers by this author Rolf Bergman, Rolf Bergman Rolf Bergman Consulting, Cleveland, OHSearch for more papers by this authorDavid Brenner, David Brenner Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorManuela Buonanno, Manuela Buonanno orcid.org/0000-0002-3455-3602 Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorEwan Eadie, Ewan Eadie orcid.org/0000-0002-7824-5580 Photobiology Unit, NHS Tayside, Ninewells Hospital and Medical School, Dundee, UKSearch for more papers by this authorPaul Donald Forbes, Paul Donald Forbes orcid.org/0000-0003-4521-8495 Toxarus, Inc., Malvern, PASearch for more papers by this authorPaul Jensen, Paul Jensen orcid.org/0000-0001-7367-4952 Final Approach Inc., Port Orange, FLSearch for more papers by this authorEdward A. Nardell, Edward A. Nardell orcid.org/0000-0002-5323-3196 Harvard Medical School, Harvard School of Public Health, Boston, MASearch for more papers by this authorDavid Sliney, Corresponding Author David Sliney david.sliney@att.net orcid.org/0000-0003-4859-5982 Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MDSearch for more papers by this authorRichard Vincent, Richard Vincent orcid.org/0000-0003-3453-4070 General Internal Medicine, Icahn School of Medicine at Mount Sinai, New York, NYSearch for more papers by this authorDavid Welch, David Welch Center for Radiological Research, Columbia University Medical Center, New York, NYSearch for more papers by this authorKenneth Wood, Kenneth Wood SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews, UKSearch for more papers by this author First published: 18 May 2021 https://doi.org/10.1111/php.13424Citations: 1AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Germicidal ultraviolet (GUV) air disinfection (also referred to as Ultraviolet Germicidal Irradiation or "UVGI"), as a control method for the transmission of airborne pathogens, has been used for more than 80 years. In 1942, upper-room GUV (disinfecting the room air by irradiating the air space above head height with air mixing) with 254 nm low-pressure mercury lamps was used very effectively to reduce the transmission of measles (the most infectious virus known) in two Philadelphia suburban schools (1-4). More recently, in the 1980s, it was also common to find UV luminaires in hospital emergency rooms, clinics, waiting rooms and operating theaters, primarily due to a global resurgence of drug-resistant tuberculosis (5). Unfortunately, interest in UV air disinfection waned primarily because drugs and vaccines became available for airborne bacterial and viral diseases such as tuberculosis, measles, mumps and chicken pox (6). However, research continued, leading to significant advances; confirmation of the efficacy and safety of upper-room GUV, new studies with ultraviolet radiation in the wavelength region 200 to 230 nm (dubbed "far-UVC") and development of ultraviolet-C (UVC) light-emitting diodes (LEDs). It is clear that aerosols are an important, if not dominant, route for SARS-CoV-2 transmission (7-11). Therefore, it is time once again to implement GUV air disinfection, with upper-room GUV still the most cost-effective way to disinfect large volumes of room air as an effective and safe control measure when installed properly and people are properly trained regarding its use (12-15). Furthermore, whole room GUV with UVC wavelengths less than 230 nm shows great promise. GUV is a "behavior independent" control measure, meaning it does not rely upon the behavior of people, for example, social distancing, cough hygiene or mask wearing. Due to its mode of action, damaging ubiquitous nucleic acids, GUV can inactivate not just SARS-CoV-2 but also its mutated variants and a wide-range of pathogens including drug-resistant bacteria (16, 17). For that reason, it is also likely to be effective against the next pandemic, whatever the pathogen. As UV inactivates pathogens by causing genetic mutations, concerns periodically arise that UV exposure could contribute to more infectious, more pathogenic or more drug-resistant pathogens. However, it is unchecked replication of virus in human populations, something which GUV is specifically designed to limit, that results in far more mutations than external exposure to GUV. However, appropriate deployment of GUV is critical. Whilst upper-room GUV radiation is highly effective for air disinfection, in contrast, walk-through UV portals and UV wands are subject to much greater challenges for surface disinfection and are also less likely to be effective. Marketing of such devices is often exaggerated, supported with scant unpublished data on safety and efficacy and, of course, they are not designed for tackling airborne transmission, an important mode of Covid-19 spread. Much larger UV exposures are required and the realities of the real world, such as macro and micro-shadows in materials and absorption by dirt and oils, are barriers to GUV being the primary surface disinfection technique. This has been known in the healthcare community for some time, where UVC surface decontamination is successfully deployed as an adjunct to manual cleaning (18). Implementation barriers for GUV include concern about the adverse health effects from exposure, but this is only an issue when the technology is misapplied. Upper-room GUV has been shown to be safe when fixtures are well-designed, properly installed, checked for safe exposure levels before being activated and properly maintained. A major attraction of UVC wavelengths below 230 nm is its frequently equivalent efficacy compare with 254 nm UVC but it is characterized by limited penetration in tissue due to its shorter wavelength (19-21). This suggests that such sources, exemplified by krypton chloride (KrCl) lamps, particularly if modified to remove energy above 230 nm, can be used to inactivate airborne microbes throughout occupied spaces while not posing a health hazard to workers in the lower room (14, 22-24). Similarly, the limited penetration depth by 254 nm radiation from low-pressure mercury GUV lamps will not pose a health hazard if the in-room exposures are kept within safe levels (25). Whilst it is undeniable that improved ventilation should be a first-line measure, in a significant proportion of buildings or transport vehicles, increasing ventilation effectiveness is not possible or is prohibitively expensive. Moreover, increasing ventilation produces declining increments in protection at escalating costs (26). In contrast, upper-room GUV systems are cost-effective and applicable to most settings with an effective ceiling height of at least 2.3 meters. In rooms with low ceilings of less than 2.3 meters, UVC wavelengths below 230 nm can be introduced as one alternative. Whilst UVC systems emitting below 230 nm are currently expensive and have limited lamp life, both these factors are likely to improve in the coming months and new technologies, emitting at the relevant wavelengths, will emerge. From our past extensive experience in GUV applications, we support specific goals to resolve current safety concerns and expedite implementation of available and appropriate technology for GUV disinfection. They include: Exploration and potential revision of exposure limits based upon recent studies including those in this Symposium in Print. Establishing guidelines and standards for the safe and effective installation, deployment and maintenance of GUV. Effective training of installers along with independent certification of competent and compliant installation and maintenance of GUV. GUV is an important and underused infection control measure. The potential benefit to health and the economy from a reduction in Covid-19 cases far outweighs risks of potential adverse health effects. Within well-established exposure limits, the risk of skin cancer and eye cataracts are vanishingly small, a tiny fraction of the risk from everyday exposure to the more penetrating ultraviolet-A and ultraviolet-B in sunlight (25). Overexposure to UVC is avoidable, but when it does occur, typically results in mild skin redness or eye irritation. Research on upper-room GUV and far-UVC will of course continue, but with the unprecedented severity of COVID-19 on health and global economy, we already know more than enough about the safety and efficacy of GUV to conclude that the benefit-risk balance is dramatically on the side of benefit. REFERENCES 1Wells, W. F., M. W. Wells and T. S. Wilder (1942) The environmental control of epidemic contagion. I. An epidemiological study of radiant disinfection of air in day schools. Amer. J. Epi. 35, 97– 121. 2Wells, W. F. and M. W. Wells (1943) Dynamics of air-borne infection. Amer. J. Med. Sci. 206, 11– 17. 3Wells, W. F. (1943) Air disinfection in day schools. Am. J. Public Health Nations Health. 33, 1436– 1443. 4Wells, M. W. (1945) Ventilation in the spread of chickenpox and measles within school rooms. J. Am. Med. Assoc. 129, 197– 200. 52013 Special Issue: Symposium in Print on Upper-Room Ultraviolet Germicidal Irradiation for Air Disinfection. Photochem. Photobiol. 89, 763– 1007. 6Reed, N. G. (2010) The history of ultraviolet germicidal irradiation for air disinfection. Public Health Rep. 125, 15– 27. 7Morawska, L. and D. K. Milton (2020) It is time to address airborne transmission of coronavirus disease 2019 (COVID-19). Clin. Infect. Dis. 71, 2311– 2313. 8 The Lancet Respiratory Medicine (2020) COVID-19 transmission—up in the air. Lancet Resp. Med. 8, 1159. 9 World Health Organization (2020) Coronavirus disease (COVID-19): How is it transmitted? Available at: https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-how-is-it-transmitted. Accessed on 26 February 2021. 10 Centers for Disease Control and Prevention (2020) Scientific Brief: SARS-CoV-2 and Potential. Available at: https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-sars-cov-2.html. Accessed 26 February 2021. 11 National Academies of Sciences, Engineering, and Medicine (2020) Airborne Transmission of SARS-CoV-2: Proceedings of a Workshop in Brief. The National Academies Press, Washington, DC. 12Mphaphlele, M., A. S. Dharmadhikari, P. A. Jensen, S. N. Rudnick, T. H. van Reenen, M. A. Pagano, W. Leuschner, T. A. Sears, S. P. Milonova, M. van der Walt, A. C. Stoltz, K. Weyer and E. A. Nardell (2015) Institutional tuberculosis transmission. Controlled trial of upper room ultraviolet air disinfection: a basis for new dosing guidelines. Am. J. of Respir. Crit. Care Med. 192, 477– 484. 13Escombe, A. R., D. A. J. Moore, R. H. Gilman, M. Navincopa, E. Ticona, B. Mitchell, C. Noakes, C. Martinez, P. Sheen, R. Ramirez, W. Quino, A. Gonzalez, J. Friedland and C. Evans (2009) Upper-room ultraviolet light and negative air ionization to prevent tuberculosis transmission. PLoS Medicine 6, e1000043. 14Buonanno, M., D. Welch, I. Shuryak and D. Brenner (2020) Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Sci. Rep. 10, 1– 8. 15 Illuminating Engineering Society (2020) IES Committee Report: Germicidal Ultraviolet (GUV) – Frequently Asked Questions. IES CR-2-2—V1. 16Kowalski, W. (2009) Ultraviolet Germicidal Irradiation Handbook: UVGI for Air and Surface Disinfection. Springer, Berlin Heidelberg. 17Ponnaiya, B., M. Buonanno, D. Welch, I. Shuryak, G. Randers-Pehrson and D. Brenner (2018) Far-UVC light prevents MRSA infection of superficial wounds in vivo. PLoS One 13, e0192053. 18Ramos, C., J. Roque, D. B. Sarmiento, L. Suarez, J. Sunio, K. Tabungar, G. Tengco, P. C. Rio and A. L. Hilario (2020) Use of ultraviolet-C in environmental sterilization in hospitals: A systematic review on efficacy and safety. Int. J. Health Sci. 14, 52– 65. 19Buonanno, M., B. Ponnaiya, D. Welch, M. Stanislauskas, G. Randers-Pehrson, L. Smilenov, D. F. Lowy, D. M. Owens and D. J. Brenner (2017) Germicidal efficacy and mammalian skin safety of 222-nm UV light. Radiat. Res. 187, 493– 501. 20Barnard, I. R. M., E. Eadie and K. Wood (2020) Further evidence that far-UVC for disinfection is unlikely to cause erythema or pre-mutagenic DNA lesions in skin. Photodermatol. Photoimmunol. Photomed. 36, 476– 477. 21Beck, S. E., R. A. Rodriguez, M. A. Hawkins, T. M. Hargy, T. C. Larason and K. G. Linden (2016) Comparison of UV-induced inactivation and RNA damage in MS2 phage across the germicidal UV spectrum. Appl. Environ. Microb. 82, 1468– 1474. 22 American Conference of Governmental Industrial Hygienists (2020) TLVs and BEIs: Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. ACGIH Worldwide, Cincinnati, OH. 23 International Commission on Non-Ionizing Radiation Protection (2004) ICNIRP Guidelines on Limits of Exposure to Ultraviolet Radiation of Wavelengths between 180 nm and 400 nm (Incoherent Optical Radiation). Health Phys. 87, 171– 186. 24Woods, J. A., A. Evans, P. D. Forbes, P. J. Coates, J. Gardner, R. M. Valentine, S. H. Ibbotson, J. Ferguson, C. Fricker and H. Moseley (2015) The effect of 222-nm UVC phototesting on healthy volunteer skin: A pilot study. Photodermatol. Photoimmunol. Photomed. 31, 159– 166. 25 International Commission on Illumination (2010) UV-C Photocarcinogenesis Risks from Germicidal Lamps. CIE Document 187. 26Nardell, E. A., J. Keegan, S. A. Cheney and S. C. Etkind (1991) Airborne infection: theoretical limits of protection achievable by building ventilation. Am. Rev. Respir. Dis. 144, 302– 306. Citing Literature Volume97, Issue3Special Issue: This Special Issue is dedicated to the topics of Germicidal Photobiology and Infection ControlMay/June 2021Pages 464-465 ReferencesRelatedInformation

With the growing success of controlling malaria in Sub-Saharan Africa, the incidence of fever due to malaria is in decline, whereas the proportion of patients with non-malaria febrile illness (NMFI) is increasing. Clinical diagnosis of NMFI is hampered by unspecific symptoms, but early diagnosis is a key factor for both better patient care and disease control. The aim of this study was to determine the arboviral aetiologies of NMFI in low resource settings, using a mobile laboratory based on recombinase polymerase amplification (RPA) assays. The panel of tests for this study was expanded to five arboviruses: dengue virus (DENV), zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), and rift valley fever virus (RVFV). One hundred and four children aged between one month and 115 months were enrolled and screened. Three of the 104 blood samples of children <10 years presented at an outpatient clinic tested positive for DENV. The results were confirmed by RT-PCR, partial sequencing, and non-structural protein 1 (NS1) antigen capture by ELISA (Biorad, France). Phylogenetic analysis of the derived DENV-1 sequences clustered them with sequences of DENV-1 isolated from Guangzhou, China, in 2014. In conclusion, this mobile setup proved reliable for the rapid identification of the causative agent of NMFI, with results consistent with those obtained in the reference laboratory’s settings.

Lighting has been recognized in the fields of human factors, ergonomics, and systems engineering, as an environmental factor that can affect wellness and performance, and the occurrence of medical error. Short wavelength (‘blue’) light is known to influence ‘non-visual’ effects of light in humans. These effects, that go beyond the pure ‘visual’ function, can affect human wellness and performance, as has been reported in previous scientific research. The aim and novelty of this research is to study the potentially beneficial ‘non-visual’ effects of lighting in the clinical environment to advance patient safety, and improve clinician wellness and performance. The hypothesis of this study was that clinician wellness and performance in the execution of clinical procedures in the emergency department (ED) could be improved through controlled, indirect, ‘blue’-regulated, full visible spectrum, tunable, solid state, ‘white’ lighting. To conduct our inquiry, we performed a crossover study with current ED clinicians that executed clinical procedures in a high-fidelity, simulated ED setting, under two different lighting conditions. We used the existing fluorescent lighting as the control condition. To provide the appropriate experimental lighting condition, we developed a novel multichannel lighting system for precise control and assessment of light delivery conditions, with specific emphasis in the short wavelength (blue light) spectral area. The results of this study suggest that it is possible that indirect, ‘blue-enriched’, full visible spectrum, ‘white’ lighting, might reduce clinician sleepiness and workload perceptions, might reduce the execution time for clinical procedures, and the occurrence of medical error, while improving clinician wellness. Future work would expand the scope of our study to advance patient safety in clinical scenarios where prevalence of adverse events has been observed, such as improvement in clinician cognitive recovery from medical error, hand-offs, and teamwork conditions. This study can also be translated to other fields of applications such as 24/7 control centers.

This investigation quantifies the upper-room ultraviolet germicidal irradiation (UVGI) efficacy in a room with a ceiling-mounted fan that blew air either upwards or downwards at three rotational speeds. The numerical modeling deployed a steady-state passive scalar (Eulerian) and particle tracking (Lagrangian) CFD with a rotating reference frame. Two wall-mounted fixtures horizontally collimated the irradiance field, which was measured with a flat sensor and imported into the numerical models. This study predicted the UVGI efficacy under an extreme range of microorganism susceptibilities to define relationships between the system performance and operational parameters. A mathematical expression with general validity for fraction remaining under perfect air-mixing conditions was analytically developed and used as a performance benchmark. The CFD predictions were validated by the experimental data, expressed as a fraction remaining at the room exhaust for two different microorganisms. Numerical predictions were in a good agreement with the experimental data. In general, the Lagrangian predictions agreed better with the measured data than the Eulerian predictions. Inclusion of a rotating fan significantly improved UVGI performance, but there was no benefit from increasing the fan speed beyond certain values. For this investigation where the microorganism source is located below the fan, the UVGI system performed most efficiently when the fan blew upward, with the optimal performance achieved for the moderate rotational speed of 107 rpm. The highest upper-room UVGI efficacy for this fan setup is due to the airflow and UV light fields enabling a delivery of the highest amount of UV irradiation to the microorganism. (C) 2015 Elsevier Ltd. All rights reserved.

This study proposes a numerical modeling method for the indoor environment with ceiling fans and upper-room ultraviolet germicidal irradiation (UR-UVGI) fixtures. The numerical modeling deployed steady-state Computational Fluid Dynamics (CFD) with a rotating reference frame to simulate the rotation of fan blades. CFD was validated with experimental data of velocity field and fraction of microorganism remaining at the exhaust diffuser. The fraction of microorganism remaining represented the ratio of the concentration of airborne microorganisms measured with UVGI turned on to the one measured with UVGI turned off. According to the validation results, the CFD model correctly reproduced the air movement induced by the rotation of ceiling fan. When the ambient ventilation rate was 2 ACH (air changes per hour) or 6 ACH, the CFD model accurately predicted the average vertical speeds in the section 2.44 m above the floor with the errors less than 10%, regardless of the ceiling fan's rotational direction or speed. In addition, the simulation results showed that the fraction of microorganism remaining increased with the ambient air exchange rate when the fan blew air downward with a rotational speed as high as 235 rpm, which corresponded with the experimental results. Furthermore, the simulation results accurately predicted the fraction of microorganism remaining when the ambient air exchange rate was 2 ACH. We conclude that this novel numerical model can reproduce the effects of ceiling fans and UR-UVGI fixtures on indoor environment, and should aid in the investigation of the impact of ceiling fans on UR-UVGI disinfection efficacy.

This study investigated the disinfection efficacy of the upper-room ultraviolet germicidal irradiation (UR-UVGI) system with ceiling fans. The investigation used the steady-state computational fluid dynamics (CFD) simulations to solve the rotation of ceiling fan with a rotating reference frame. Two ambient air exchange rates, 2 and 6 air changes per hour (ACH), and four downward fan rotational speeds, 0, 80, 150 and 235rpm were considered. In addition, the passive scalar concentration simulations incorporated ultraviolet (UV) dose by two methods: one based on the total exposure time and average UV fluence rate, and another based on SVE3* (New Scale for Ventilation Efficiency 3), originally defined to evaluate the mean age of the air from an air supply opening. Overall, the CFD results enabled the evaluation of UR-UVGI disinfection efficacy using different indices, including the fraction of remaining microorganisms, equivalent air exchange rate, UR-UVGI effectiveness and tuberculosis infection probability by the Wells-Riley equation. The results indicated that air exchange rate was the decisive factor for determining UR-UVGI performance in disinfecting indoor air. Using a ceiling fan could also improve the performance in general. Furthermore, the results clarified the mechanism for the ceiling fan to influence UR-UVGI disinfection efficacy.

Upper-room ultraviolet germicidal irradiation (UVGI) has several applications, its most important use is to reduce tuberculosis transmission in high-burden, resource-limited settings, especially those dealing with epidemics of drug-resistant disease. The efficacy of upper-room (UVGI) to reduce the transmission of airborne infection in real-world settings is no longer in question. International application (dosing) guidelines are needed, as are safety standards and commissioning procedures. A recent symposium to build consensus on guidelines discussed specifications for affordable UVGI fixture designs, safety, performance, computer-aided design (CAD) for UVGI, maintenance, dosimetry, gonioradiometric measurement and innovation using germicidal LEDs.

A commercial computer-aided design tool used by the lighting industry was modified to predict fluence rates for upper-room ultraviolet germicidal irradiation. Experimental validation based on more than 1600 measurements and 3 types of commercial ultraviolet fixtures, which was done in an experimental chamber and in a homeless shelter having fixtures in continuous use for over 7 years, showed differences in measured and predicted average upper-room fluence rates of less than 10%. The computer-aided design tool, however, was not very successful at predicting fluence rates at specific room locations, a capability that is needed for mating computational fluid dynamics with ultraviolet germicidal irradiation. Although not an objective of this study, it was also found that the three types of fixtures used in this study have surprisingly significant differences in efficiency based on fixture ultraviolet power output and electrical input. One fixture type had an efficiency that was more than five times that of another. For comparison purposes, a standard method for measuring and reporting fixture efficiency is needed.

Ultraviolet germicidal irradiation (UVGI), 254 nm UV-C, is increasingly used as an infection control strategy to reduce the spread of airborne pathogens such as tuberculosis (TB), influenza viruses, and measles. With the appearance of multidrug-resistant TB and emerging infectious disease such as severe acute respiratory syndrome (SARS) and H1N1 influenza viruses, engineering controls using 254 nm UV-C lamps within specialized luminaires, herein designated UVGI fixtures, are being installed in high-risk settings such as homeless shelters, hospitals, jails and prisons, and schools. Studies have established that a relatively uniform spatial distribution of UV-C in the upper room can effectively cleanse the air of aerosolized pathogens. However, for planning purposes, the placement of multiple UVGI fixtures in a space, to achieve uniformity of UV-C energy distribution using currently available lighting software, is not yet practical because no industry-wide standard method exists for radiometric measurement of commercial UVGI fixtures. In this article, standard methods for photometry and reporting of general fluorescent lighting luminaire photometric data are adopted to provide UVGI fixture spatial emission distribution data in an electronic file format. The ultimate expectation of the authors is that the results will lead to a software program for fixture placement, comparable to and as easy to use as the corresponding software used for general interior lighting applications. To accomplish this goal, a radiometry measurement system is developed to obtain the radiant intensity distributions of UVGI fixtures in a three-dimensional space. This system includes a moving-mirror Type C goniometer, a mirror, a radiometer, a desktop computer, the mechanical control hardware, and the data acquisition/presentation software. Repeated measurements were made on each of three exemplary UVGI fixtures, and measurement variation did not exceed ± 2.0%.

Concerns about the safety of Ultraviolet Germicidal Irradiation (UVGI) applications on human beings have been an issue at least since the introduction of this technology for practical use in the 1930s. The resurgence of tuberculosis (TB) in the United States in the mid-1980s led to a revival of interest in UV technology, a focus that had almost disappeared because alternate means of controlling TB had inaccurately been deemed successful. These failures in TB control led to a revival of UVGI use. And with that revival grew necessary and appropriate concerns about attempts to eliminate human overexposure. For all those working in the field of UVGI, safety issues must be a concern because when UVGI fixtures are placed improperly, or precautions ignored, room occupants are placed at risk of photokeratoconjunctivitis and photodermatitis. If safety is so prominent a concern, why do incidents of UV side effects continue to occur? See Murphy's Law.

In order to optimize the use of ceiling fans to improve upper-room UVGI's disinfection efficacy in various indoor settings, this study proposed a validated CFD (Computational Fluid Dynamics) approach for the numerical parametric investigation of the integrated application of ceiling fan and upper-room UVGI. This CFD approach is based on the Eulerian method with a rotating reference frame accounting for the rotation of fan blades. The approach is validated with the experimental data in terms of velocity distribution and fraction remaining, which is the ratio of the steady-state airborne microorganism concentration with the UVGI turned "on" to the steady-state concentration with the UVGI turned "off". According to the results, the CFD approach well reproduced the fan-induced airflow field and predicted the change of velocity components at the elevations of 20 cm above and 20 cm below the fan blades, when ambient ventilation was as small as 0.5 ACH. However, it overestimated the average vertical speeds in the section 4 cm below the fan blades with the errors less than 10%. In addition, the numerical approach underestimated the fraction remaining when air exchange rate was 6 ACH and ceiling fan blew air downward at a speed of 235 rpm. The simulation results also consisted with the experimental data that the disinfection efficacy decreased with the increase of air exchange rate when the fan speed was 235 rpm. Overall, CFD is a suitable tool to parametrically investigate ceiling fan's influence on upper-room UVGI's disinfection efficacy.