Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines

Reducing Transmission of Airborne Respiratory Pathogens: A New Beginning as the COVID-19 Emergency Ends

BACKGROUND

In response to the COVID-19 pandemic, new evidence-based strategies have emerged for reducing transmission of respiratory infections through management of indoor air.

OBJECTIVES

This paper reviews critical advances that could reduce the burden of disease from inhaled pathogens and describes challenges in their implementation.

DISCUSSION

Proven strategies include assuring sufficient ventilation, air cleaning by filtration, and air disinfection by germicidal ultraviolet (UV) light. Layered intervention strategies are needed to maximize risk reduction. Case studies demonstrate how to implement these tools while also revealing barriers to implementation. Future needs include standards designed with infection resilience and equity in mind, buildings optimized for infection resilience among other drivers, new approaches and technologies to improve ventilation, scientific consensus on the amount of ventilation needed to achieve a desired level of risk, methods for evaluating new air-cleaning technologies, studies of their long-term health effects, workforce training on ventilation systems, easier access to federal funds, demonstration projects in schools, and communication with the public about the importance of indoor air quality and actions people can take to improve it. https://doi.org/10.1289/EHP13878.

222 nm Far-UVC from filtered Krypton-Chloride excimer lamps does not cause eye irritation when deployed in a simulated office environment

Far-UVC, from filtered Krypton-Chloride lamps, is promising for reducing airborne transmission of disease. While significant research has been undertaken to investigate skin safety of these lamps, less work has been undertaken on eye safety. There is limited data on human eye safety or discomfort from the deployment of this germicidal technology. In this pilot study, immediate and delayed eye discomfort were assessed in a simulated office environment with deployment of Krypton-Chloride lamps, located on the ceiling and directed downwards into the occupied room. Discomfort was assessed immediately postexposure and several days after exposure using validated, Standard Patient Evaluation Eye Dryness (SPEED) and Ocular Surface Disease Index (OSDI) questionnaires. Our results show no significant eye discomfort or adverse effects from the deployment of Far-UVC in this simulated office environment, even when lamps were operated continuously with participants receiving head exposures of up to 50 mJ cm-2 . In addition, a statistically significant reduction in bacteria and fungi of 52% was observed. Far-UVC in this simulated office environment did not cause any clinically significant eye discomfort and was effective at reducing pathogens in the room. These results contribute an important step to further investigation of the interaction of Far-UVC with the human eye.

Time to change the way we think about tuberculosis infection prevention and control in health facilities: insights from recent research

In clinical settings where airborne pathogens, such as Mycobacterium tuberculosis, are prevalent, they constitute an important threat to health workers and people accessing healthcare. We report key insights from a 3-year project conducted in primary healthcare clinics in South Africa, alongside other recent tuberculosis infection prevention and control (TB-IPC) research. We discuss the fragmentation of TB-IPC policies and budgets; the characteristics of individuals attending clinics with prevalent pulmonary tuberculosis; clinic congestion and patient flow; clinic design and natural ventilation; and the facility-level determinants of the implementation (or not) of TB-IPC interventions. We present modeling studies that describe the contribution of M. tuberculosis transmission in clinics to the community tuberculosis burden and economic evaluations showing that TB-IPC interventions are highly cost-effective. We argue for a set of changes to TB-IPC, including better coordination of policymaking, clinic decongestion, changes to clinic design and building regulations, and budgeting for enablers to sustain implementation of TB-IPC interventions. Additional research is needed to find the most effective means of improving the implementation of TB-IPC interventions; to develop approaches to screening for prevalent pulmonary tuberculosis that do not rely on symptoms; and to identify groups of patients that can be seen in clinic less frequently.

Evaluating the efficacy of a rotating upper-room UVC-LED irradiation device in inactivating aerosolized Escherichia coli under different disinfection ranges, air mixing, and irradiation conditions

Cost-effective and safe air disinfection methods are urgently needed in various environmental public settings. A novel UVC-based disinfection system was designed and tested to provide a promising solution because of its effective inactivation of indoor bioaerosols at a low cost. UVC light-emitting diodes (UVC-LEDs) were utilized as the irradiation source. This system has the unique feature of rotating the UVC-LEDs to generate a "scanning irradiation" zone. Escherichia coli was aerosolized into an experimental chamber, exposed to UVC-LEDs, and sampled using an impactor. Effects of air mixing (well-mixed vs. poorly-mixed), transmission range (short vs. long), and irradiation mode (stationary vs. rotating) were evaluated. The system performs significantly well under the poorly-mixed condition. The results obtained from the short disinfection range indicate that the rotating UVC was approximately 70.5 % more effective than the stationary UVC for the poorly-mixed case. Further, we evaluated the performance of the long disinfection range under a poorly-mixed situation, and the disinfection efficacy was 84.6 % higher for the rotating irradiation than that of the stationary. About 0.59-1.34 J/m² UV dose can be used to obtain one-log inactivation of E. coli. In conclusion, the novel rotating upper-room UVC-LED system is effective in reducing indoor pathogen transmission, and our findings are highly significant to a growing field where LEDs are applied for disinfection.

UV-C Light Completely Blocks Aerosol Transmission of Highly Contagious SARS-CoV-2 Variants WA1 and Delta in Hamsters

Behavioral and medical control measures have not been effective in containing the spread of SARS-CoV-2 in large part due to the unwillingness of populations to adhere to "best practices". Ultraviolet light with wavelengths of between 200 and 280 nm (UV-C) and, in particular, germicidal ultraviolet light, which refers to wavelengths around 254 nm, have the potential to unobtrusively reduce the risk of SARS-CoV-2 transmission in enclosed spaces. We investigated the effectiveness of a strategy using UV-C light to prevent airborne transmission of the virus in a hamster model. Treatment of environmental air with 254 nm UV-C light prevented transmission of SARS-CoV-2 between individuals in a model using highly susceptible Syrian golden hamsters. The prevention of transmission of SARS-CoV-2 in a natural system by treating elements of the surrounding environment is one more weapon in the arsenal to combat COVID. The results presented indicate that coupling mitigation strategies utilizing UV-C light, along with current methods to reduce transmission risk, have the potential to allow a return to normal indoor activities.

Airborne Transmission and Control of Influenza and Other Respiratory Pathogens

Despite uncertainty about the specific transmission risk posed by airborne, spray-borne, and contact modes for influenza, SARS-CoV-2, and other respiratory viruses, there is evidence that airborne transmission via inhalation is important and often predominates. An early study of influenza transmission via airborne challenge quantified infectious doses as low as one influenza virion leading to illness characterized by cough and sore throat. Other studies that challenged via intranasal mucosal exposure observed high doses required for similarly symptomatic respiratory illnesses. Analysis of the Evaluating Modes of Influenza Transmission (EMIT) influenza human-challenge transmission trial—of 52 H3N2 inoculated viral donors and 75 sero-susceptible exposed individuals—quantifies airborne transmission and provides context and insight into methodology related to airborne transmission. Advances in aerosol sampling and epidemiologic studies examining the role of masking, and engineering-based air hygiene strategies provide a foundation for understanding risk and directions for new work.

A review of facilities management interventions to mitigate respiratory infections in existing buildings

The Covid-19 pandemic reveals that the hazard of the respiratory virus was a secondary consideration in the design, development, construction, and management of public and commercial buildings. Retrofitting such buildings poses a significant challenge for building owners and facilities managers. This article reviews current research and practices in building operations interventions for indoor respiratory infection control from the perspective of facilities managers to assess the effectiveness of available solutions. This review systematically selects and synthesises eighty-six articles identified through the PRISMA process plus supplementary articles identified as part of the review process, that deal with facilities' operations and maintenance (O&M) interventions. The paper reviewed the context, interventions, mechanisms, and outcomes discussed in these articles, concluding that interventions for respiratory virus transmission in existing buildings fall into three categories under the Facilities Management (FM) discipline: Hard services (HVAC and drainage system controls) to prevent aerosol transmissions, Soft Services (cleaning and disinfection) to prevent fomite transmissions, and space management (space planning and occupancy controls) to eliminate droplet transmissions. Additionally, the research emphasised the need for FM intervention studies that examine occupant behaviours with integrated intervention results and guide FM intervention decision-making. This review expands the knowledge of FM for infection control and highlights future research opportunities.

Direct estimates of absolute ventilation and estimated Mycobacterium tuberculosis transmission risk in clinics in South Africa

Healthcare facilities are important sites for the transmission of pathogens spread via bioaerosols, such as Mycobacterium tuberculosis. Natural ventilation can play an important role in reducing this transmission. We aimed to measure rates of natural ventilation in clinics in KwaZulu-Natal and Western Cape provinces, South Africa, then use these measurements to estimate Mycobacterium tuberculosis transmission risk. We measured ventilation in clinic spaces using a tracer-gas release method. In spaces where this was not possible, we estimated ventilation using data on indoor and outdoor carbon dioxide levels. Ventilation was measured i) under usual conditions and ii) with all windows and doors fully open. Under various assumptions about infectiousness and duration of exposure, measured absolute ventilation rates were related to risk of Mycobacterium tuberculosis transmission using the Wells-Riley Equation. In 2019, we obtained ventilation measurements in 33 clinical spaces in 10 clinics: 13 consultation rooms, 16 waiting areas and 4 other clinical spaces. Under usual conditions, the absolute ventilation rate was much higher in waiting rooms (median 1769 m3/hr, range 338-4815 m3/hr) than in consultation rooms (median 197 m3/hr, range 0-1451 m3/hr). When compared with usual conditions, fully opening existing doors and windows resulted in a median two-fold increase in ventilation. Using standard assumptions about infectiousness, we estimated that a health worker would have a 24.8% annual risk of becoming infected with Mycobacterium tuberculosis, and that a patient would have an 0.1% risk of becoming infected per visit. Opening existing doors and windows and rearranging patient pathways to preferentially use better ventilated clinic spaces result in important reductions in Mycobacterium tuberculosis transmission risk. However, unless combined with other tuberculosis infection prevention and control interventions, these changes are insufficient to reduce risk to health workers, and other highly exposed individuals, to acceptable levels.

Modelling the effect of infection prevention and control measures on rate of Mycobacterium tuberculosis transmission to clinic attendees in primary health clinics in South Africa

BACKGROUND

Elevated rates of tuberculosis in healthcare workers demonstrate the high rate of Mycobacterium tuberculosis (Mtb) transmission in health facilities in high-burden settings. In the context of a project taking a whole systems approach to tuberculosis infection prevention and control (IPC), we aimed to evaluate the potential impact of conventional and novel IPC measures on Mtb transmission to patients and other clinic attendees.

METHODS

An individual-based model of patient movements through clinics, ventilation in waiting areas, and Mtb transmission was developed, and parameterised using empirical data from eight clinics in two provinces in South Africa. Seven interventions-codeveloped with health professionals and policy-makers-were simulated: (1) queue management systems with outdoor waiting areas, (2) ultraviolet germicidal irradiation (UVGI) systems, (3) appointment systems, (4) opening windows and doors, (5) surgical mask wearing by clinic attendees, (6) simple clinic retrofits and (7) increased coverage of long antiretroviral therapy prescriptions and community medicine collection points through the Central Chronic Medicine Dispensing and Distribution (CCMDD) service.

RESULTS

In the model, (1) outdoor waiting areas reduced the transmission to clinic attendees by 83% (IQR 76%-88%), (2) UVGI by 77% (IQR 64%-85%), (3) appointment systems by 62% (IQR 45%-75%), (4) opening windows and doors by 55% (IQR 25%-72%), (5) masks by 47% (IQR 42%-50%), (6) clinic retrofits by 45% (IQR 16%-64%) and (7) increasing the coverage of CCMDD by 22% (IQR 12%-32%).

CONCLUSIONS

The majority of the interventions achieved median reductions in the rate of transmission to clinic attendees of at least 45%, meaning that a range of highly effective intervention options are available, that can be tailored to the local context. Measures that are not traditionally considered to be IPC interventions, such as appointment systems, may be as effective as more traditional IPC measures, such as mask wearing.

Occupational Risk of Airborne Mycobacterium tuberculosis Exposure: A Situational Analysis in a Three-Tier Public Healthcare System in South Africa

This study aimed to detect airborne Mycobacterium tuberculosis (MTB) at nine public health facilities in three provinces of South Africa and determine possible risk factors that may contribute to airborne transmission. Personal samples (n = 264) and stationary samples (n = 327) were collected from perceived high-risk areas in district, primary health clinics (PHCs) and TB facilities. Quantitative real-time (RT) polymerase chain reaction (PCR) was used for TB analysis. Walkabout observations and work practices through the infection prevention and control (IPC) questionnaire were documented. Statistical analysis was carried out using Stata version 15.2 software. Airborne MTB was detected in 2.2% of samples (13/572), and 97.8% were negative. District hospitals and Western Cape province had the most TB-positive samples and identified risk areas included medical wards, casualty, and TB wards. MTB-positive samples were not detected in PHCs and during the summer season. All facilities reported training healthcare workers (HCWs) on TB IPC. The risk factors for airborne MTB included province, type of facility, area or section, season, lack of UVGI, and ineffective ventilation. Environmental monitoring, PCR, IPC questionnaire, and walkabout observations can estimate the risk of TB transmission in various settings. These findings can be used to inform management and staff to improve the TB IPC programmes.

Prevention of SARS-CoV-2 (COVID-19) transmission in residential aged care using ultraviolet light (PETRA): a two-arm crossover randomised controlled trial protocol

Background

SARS-CoV-2 poses a considerable threat to those living in residential aged care facilities (RACF). RACF COVID-19 outbreaks have been characterised by the rapid spread of infection and high rates of severe disease and associated mortality. Despite a growing body of evidence supporting airborne transmission of SARS-CoV-2, current infection control measures in RACF including hand hygiene, social distancing, and sterilisation of surfaces, focus on contact and droplet transmission. Germicidal ultraviolet (GUV) light has been used widely to prevent airborne pathogen transmission. Our aim is to investigate the efficacy of GUV technology in reducing the risk of SARS-CoV-2 infection in RACF.

Methods

A multicentre, two-arm double-crossover, randomised controlled trial will be conducted to determine the efficacy of GUV devices to reduce respiratory viral transmission in RACF, as an adjunct to existing infection control measures. The study will be conducted in partnership with three aged care providers in metropolitan and regional South Australia. RACF will be separated into paired within-site zones, then randomised to intervention order (GUV or control). The initial 6-week period will be followed by a 2-week washout before crossover to the second 6-week period. After accounting for estimated within-zone and within-facility correlations of infection, and baseline infection rates (10 per 100 person-days), a sample size of n = 8 zones (n = 40 residents/zone) will provide 89% power to detect a 50% reduction in symptomatic infection rate. The primary outcome will be the incidence rate ratio of combined symptomatic respiratory infections for intervention versus control. Secondary outcomes include incidence rates of hospitalisation for complications associated with respiratory infection; respiratory virus detection in facility air and fomite samples; rates of laboratory confirmed respiratory illnesses and genomic characteristics.

Discussion

Measures that can be deployed rapidly into RACF, that avoid the requirement for changes in resident and staff behaviour, and that are effective in reducing the risk of airborne SARS-CoV-2 transmission, would provide considerable benefit in safeguarding a highly vulnerable population. In addition, such measures might substantially reduce rates of other respiratory viruses, which contribute considerably to resident morbidity and mortality.

Trial registration Australian and New Zealand Clinical Trials Registry ACTRN12621000567820 (registered on 14th May, 2021).

Simulated sunlight decreases the viability of SARS-CoV-2 in mucus

The novel coronavirus, SARS-CoV-2, has spread into a pandemic since its emergence in Wuhan, China in December of 2019. This has been facilitated by its high transmissibility within the human population and its ability to remain viable on inanimate surfaces for an extended period. To address the latter, we examined the effect of simulated sunlight on the viability of SARS-CoV-2 spiked into tissue culture medium or mucus. The study revealed that inactivation took 37 minutes in medium and 107 minutes in mucus. These times-to-inactivation were unexpected since they are longer than have been observed in other studies. From this work, we demonstrate that sunlight represents an effective decontamination method but the speed of decontamination is variable based on the underlying matrix. This information has an important impact on the development of infection prevention and control protocols to reduce the spread of this deadly pathogen.

Innovation and possible long-term impact driven by COVID-19: Manufacturing, personal protective equipment and digital technologies

It is known that discrete events causing extreme societal and economic pressures as well as technological opportunity are major driving factors of innovation. Due to the presence of both of these factors during the COVID-19 pandemic it was hypothesized that there would be significant on-going innovation throughout society during the pandemic, with many of the innovations having the ability to have long-term societal impact. Analysis of literature and patent databases determined sectors of accelerated innovation to include manufacturing, personal protective equipment and digital technologies. The ability of flexible and advanced manufacturing technologies to provide more adaptable production capabilities that are less susceptible to disruption, make it likely that these technologies will be incorporated further, changing the way many manufacturing firms operate. Collaboration has increased, demonstrating increases in problem-solving efficiency; however, concerns around intellectual property is likely to reduce the long-term impact of these procedural changes. Advancements in personal protective equipment and disinfection technologies may have the long-term impact of reducing waste production and triggering changes in cleaning protocols throughout society. Digital technologies such as telemedicine, data collection, artificial intelligence and communication technologies were found to have undergone significant innovation, with possible impacts such as large-scale systemic shifts, and changes in how governments, corporations, the scientific community and the public interact.

Critical Design Parameters in Design and Efficacy of Upper-Room UVC254 Luminaire Systems: Part I: Overview of Major Parameters and Relationships†

During the current SARS‐CoV‐2 and tuberculosis global pandemics, public health and infection prevention and control professionals wrestle with cost‐effective means to control airborne transmission. One technology recommended by Centers for Disease Control and Prevention and the World Health Organization for lowering indoor concentration of these and other microorganisms and viruses is upper‐room ultraviolet 254 nm (UVC₂₅₄) systems. Applying both a material balance as well as some nondimensional parameters developed by Rudnick and First, the impact of several critical parameters and their effect on the fraction of microorganisms surviving UVC₂₅₄ exposure was evaluated. Vertical airspeed showed a large impact at velocities <0.05 m s⁻¹ but a lesser effect at velocities >0.05 m s⁻¹. In addition, the efficacy of any upper‐room UVC system is influenced greatly by the mean room fluence rate as opposed to a simple volume‐ or area‐based dosing criteria. An alternative UVC₂₅₄ dosing strategy was developed based on the fluence rate as a function of the UVC₂₅₄ luminaire output (W) and the square root of the product of the room volume and the ceiling height.

Air Disinfection for Airborne Infection Control with a Focus on COVID-19: Why Germicidal UV is Essential†

Aerosol transmission is now widely accepted as the principal way that COVID‐19 is spread, as has the importance of ventilation—natural and mechanical. But in other than healthcare facilities, mechanical ventilation is designed for comfort, not airborne infection control, and cannot achieve the 6 to 12 room air changes per hour recommended for airborne infection control. More efficient air filters have been recommended in ventilation ducts despite a lack of convincing evidence that SARS‐CoV‐2 virus spreads through ventilation systems. Most transmission appears to occur in rooms where both an infectious source COVID‐19 case and other susceptible occupants share the same air. Only two established room‐based technologies are available to supplement mechanical ventilation: portable room air cleaners and upper room germicidal UV air disinfection. Portable room air cleaners can be effective, but performance is limited by their clean air delivery rate relative to room volume. SARS‐CoV‐2 is highly susceptible to GUV, an 80‐year‐old technology that has been shown to safely, quietly, effectively and economically produce the equivalent of 10 to 20 or more air changes per hour under real life conditions. For these reasons, upper room GUV is the essential engineering intervention for reducing COVID‐19 spread.

Healthcare worker protection against epidemic viral respiratory disease

Lower respiratory infections are often caused or precipitated by viruses and are a leading cause of global morbidity and mortality. Mutations in these viral genomes can produce highly infectious strains that transmit across species and have the potential to initiate epidemic, or pandemic, human viral respiratory disease. Transmission between humans primarily occurs via the airborne route and is accelerated by our increasingly interconnected and globalised society. To this date, there have been four major human viral respiratory outbreaks in the 21st century. Healthcare workers (HCWs) are at particular risk during respiratory epidemics or pandemics. This is due to crowded working environments where social distancing, or wearing respiratory personal protective equipment for prolonged periods, might prove difficult, or performing medical procedures that increase exposure to virus-laden aerosols, or bodily fluids. This review aims to summarise the evidence and approaches to occupational risk and protection of HCWs during epidemic or pandemic respiratory viral disease.

Bare-bulb Upper-Room Germicidal Ultraviolet-C (GUV) Indoor Air Disinfection for COVID-19†

Reliable indoor air disinfection could make clinical and other necessary indoor spaces safer during epidemics with airborne transmission like COVID‐19. Low‐dose upper‐room germicidal ultraviolet‐C (GUV 254 nm) is well suited for this because of the SARS‐CoV‐2 virus' sensitivity to GUV inactivation and GUV's relatively easy adaptability to many types of indoor spaces without respect to outside weather conditions. However, most existing upper‐room GUV fixtures are relatively expensive and inefficient at creating an upper‐room disinfection zone due to loss of disinfecting UV‐C photons caused by the casing and louvers designed to protect persons in the occupied space. Presented herein are two moderate‐size restaurant spaces, 900 ft² (83.6 m²) and 630 ft² (58.5 m²), respectively, in which low‐cost bare‐bulb GUV fixtures, without exterior casing, were installed with upward‐pulling ceiling fans to provide upper‐room disinfection and lower‐room safety. Proper safety‐tested installations like these are adaptable to hospital emergency department waiting rooms, clinics, nursing home and prison common areas, public libraries, schools and restaurants.

Upper-room ultraviolet air disinfection might help to reduce COVID-19 transmission in buildings: a feasibility study

As the world's economies come out of the lockdown imposed by the COVID-19 pandemic, there is an urgent need for technologies to mitigate COVID-19 transmission in confined spaces such as buildings. This feasibility study looks at one such technology, upper-room ultraviolet (UV) air disinfection, that can be safely used while humans are present in the room space, and which has already proven its efficacy as an intervention to inhibit the transmission of airborne diseases such as measles and tuberculosis. Using published data from various sources, it is shown that the SARS-CoV-2 virus, the causative agent of COVID-19, is highly likely to be susceptible to UV-C damage when suspended in air, with a UV susceptibility constant likely to be in the region 0.377-0.590 m²/J, similar to that for other aerosolised coronaviruses. As such, the UV-C flux required to disinfect the virus is expected to be acceptable and safe for upper-room applications. Through analysis of expected and worst-case scenarios, the efficacy of the upper-room UV-C approach for reducing COVID-19 transmission in confined spaces (with moderate but sufficient ceiling height) is demonstrated. Furthermore, it is shown that with SARS-CoV-2, it should be possible to achieve high equivalent air change rates using upper-room UV air disinfection, suggesting that the technology might be particularly applicable to poorly ventilated spaces.

Control Measures for SARS-CoV-2: A Review on Light-Based Inactivation of Single-Stranded RNA Viruses

SARS-CoV-2 is a single-stranded RNA virus classified in the family Coronaviridae. In this review, we summarize the literature on light-based (UV, blue, and red lights) sanitization methods for the inactivation of ssRNA viruses in different matrixes (air, liquid, and solid). The rate of inactivation of ssRNA viruses in liquid was higher than in air, whereas inactivation on solid surfaces varied with the type of surface. The efficacy of light-based inactivation was reduced by the presence of absorptive materials. Several technologies can be used to deliver light, including mercury lamp (conventional UV), excimer lamp (UV), pulsed-light, and light-emitting diode (LED). Pulsed-light technologies could inactivate viruses more quickly than conventional UV-C lamps. Large-scale use of germicidal LED is dependent on future improvements in their energy efficiency. Blue light possesses virucidal potential in the presence of exogenous photosensitizers, although femtosecond laser (ultrashort pulses) can be used to circumvent the need for photosensitizers. Red light can be combined with methylene blue for application in medical settings, especially for sanitization of blood products. Future modelling studies are required to establish clearer parameters for assessing susceptibility of viruses to light-based inactivation. There is considerable scope for improvement in the current germicidal light-based technologies and practices.

A novel upper-room UVC-LED irradiation system for disinfection of indoor bioaerosols under different operating and airflow conditions

The potential of inactivating indoor bacteria aerosols using a novel rotating ultraviolet-C (UV-C) light-emitting-diode (LED) system was investigated. The system was installed in the upper level of a full scale chamber and its effectiveness against aerosolized E. coli, S. marcescens, and S. epidermidis under the well-mixed with stationary UV-LED scenario was initially tested. The estimated susceptibility values were 1.068, 1.148, and 0.156 m²/J for E. coli, S. marcescens, and S. epidermidis, respectively. Three additional scenarios of experiments were conducted, in which E. coli was aerosolized into the test chamber and then allowed to decay under (i) poorly-mixed condition with stationary system, (ii) well-mixed with rotating system, and (iii) poorly-mixed conditions with rotating system. Our results showed no significant difference between the performance of stationary and rotating UR-UVGI-LED systems under a well-mixed condition. While the performance of the stationary UR-UVGI-LED system under a poorly-mixed condition decreased by 52.90-79.38 % compared to a well-mixed condition, rotating the UR-UVGI-LED system under a poorly-mixed condition, compared to the stationary system, enhanced its performance by 22.36-49.86 %. Thus, our proposed rotating irradiation offers great potential for application in environments where bioaerosols are unevenly distributed in a built environment.

Back to Normal: An Old Physics Route to Reduce SARS-CoV-2 Transmission in Indoor Spaces

We advocate the widespread use of UV-C light as a short-term, easily deployable, and affordable way to limit virus spread in the current SARS-CoV-2 pandemic. Radical social distancing with the associated shutdown of schools, restaurants, sport clubs, workplaces, and traveling has been shown to be effective in reducing virus spread, but its economic and social costs are unsustainable in the medium term. Simple measures like frequent handwashing, facial masks, and other physical barriers are being commonly adopted to prevent virus transmission. However, their efficacy may be limited, particularly in shared indoor spaces, where, in addition to airborne transmission, elements with small surface areas such as elevator buttons, door handles, and handrails are frequently used and can also mediate transmission. We argue that additional measures are necessary to reduce virus transmission when people resume attending schools and jobs that require proximity or some degree of physical contact. Among the available alternatives, UV-C light satisfies the requirements of rapid, widespread, and economically viable deployment. Its implementation is only limited by current production capacities, an increase of which requires swift intervention by industry and authorities.

The Effectiveness of Individual and Environmental Infection Control Measures in Reducing the Transmission of Mycobacterium tuberculosis: A Systematic Review

Background

Transmission of Mycobacterium tuberculosis in healthcare settings is a preventable driver of the global tuberculosis epidemic. We aimed to assess the evidence for infection control interventions, including cough etiquette, engineering and personal respiratory protection measures, to prevent transmission of M. tuberculosis in healthcare settings.

Methods

Three independent systematic reviews were performed using 6 databases and clinical trials websites. Randomized trials, cohort studies, before-after studies, and case-control studies were included. Searches were performed for controlled studies evaluating respiratory hygiene, engineering, and personal respiratory protection measures. Outcome measures included the incidence of tuberculosis infection and disease. Studies involving transmission to either humans or animals were included.

Results

Evaluation of respiratory hygiene and cough etiquette interventions identified 4 human studies, with 22 855 participants, and 1 guinea pig study. Studies in humans evaluated the effects of multiple concurrent interventions. Patient use of surgical masks reduced infection by 14.8%, and tuberculosis disease was reduced by between 0.5% and 28.9%. Engineering and environmental interventions were evaluated in 10 studies of humans, including 31 776 human participants, and 2 guinea pig studies. Mechanical ventilation was associated with between 2.9% and 14% less infection. Nine studies of personal respiratory protection were included, including 33 913 participants. Infection was reduced by between 0% and 14.8% in studies where particulate respirators were used. The quality of included studies was assessed as low.

Conclusions

Respiratory hygiene, engineering, and environmental infection controls and personal respiratory protection interventions were associated with reduced transmission of M. tuberculosis and reduced tuberculosis disease in healthcare settings.

Preventing Transmission of Mycobacterium Tuberculosis-A Refocused Approach

Traditional tuberculosis (TB) infection control focuses on the known patient with TB, usually on appropriate treatment. A refocused, intensified TB infection control approach is presented. Combined with active case finding and rapid molecular diagnostics, an approach called FAST is described as a convenient way to call attention to the untreated patient. Natural ventilation is the mainstay of air disinfection in much of the world. Germicidal ultraviolet technology is the most sustainable approach to air disinfection under resource-limited conditions. Testing and treatment of latent TB infection works to prevent reactivation but requires greater risk targeting in both low- and high-risk settings.

Perceived Health System Barriers to Tuberculosis Control Among Health Workers in South Africa

Background

The healthcare workforce in high tuberculosis burden countries such as South Africa is at elevated risk of tuberculosis infection and disease with adverse consequences for their well-being and productivity. Despite the availability of international guidelines on protection of health workers from tuberculosis, research globally has focused on proximal deficiencies in practice rather than on health system barriers.

Objective

This study sought to elicit perceptions of informed persons within the health system regarding health system barriers to protecting health workers from tuberculosis.

Methods

Semi-structured interviews were conducted with 18 informants active in spheres related to workplace tuberculosis prevention and management in South Africa. Interviews were audio recorded and transcribed verbatim, validated and analysed to derive emergent themes. Responses were analysed using the World Health Organization building blocks as core elements of a health system bearing on protection of its health workforce.

Findings

The following health system barriers were identified by informants: leadership and governance were "top-down" and fragmented; lack of funding was a major barrier; there were insufficient numbers of staff trained in infection prevention and control and occupational health; occupational health services were not comprehensively available and the ability to sustain protective technologies was questioned. A cross-cutting barrier was lack of priority afforded to workforce occupational health associated with lack of accurate information on cases of TB among health workers.

Conclusions

We conclude that deficiencies in implementation of recommended infection control and tuberculosis management practices are unlikely to be corrected until health system barriers are addressed. More committed leadership from senior health system management and greater funding are needed. The process could be assisted by the development of indicators to characterise such barriers and monitor progress.

Treatment as prevention and other interventions to reduce transmission of multidrug-resistant tuberculosis

Drug-resistant tuberculosis (DR-TB) represents a major programmatic challenge at the national and global levels. Only ∼30% of patients with multidrug-resistant TB (MDR-TB) were diagnosed, and ∼25% were initiated on treatment for MDR-TB in 2016. Increasing evidence now points towards primary transmission of DR-TB, rather than inadequate treatment, as the main driver of the DR-TB epidemic. The cornerstone of DR-TB transmission prevention should be earlier diagnosis and prompt initiation of effective treatment for all patients with DR-TB. Despite the extensive scale-up of Xpert^® MTB/RIF testing, major implementation barriers continue to limit its impact. Although there is longstanding evidence in support of the rapid impact of treatment on patient infectiousness, delays in the initiation of effective DR-TB treatment persist, resulting in ongoing transmission. However, it is also imperative to address the burden of latent drug-resistant tuberculous infection because it is estimated that many DR-TB patients will become infectious before seeking care and encounter various diagnostic delays before treatment. Addressing latent DR-TB primarily consists of identifying, treating and following the contacts of patients with MDR-TB, typically through household contact evaluation. Adjunctive measures, such as improved ventilation and use of germicidal ultraviolet technology can further reduce TB transmission in high-risk congregate settings. Although many gaps remain in our biological understanding of TB transmission, implementation barriers to early diagnosis and rapid initiation of effective DR-TB treatment can and must be overcome if we are to impact DR-TB incidence in the short and long term.

Emergency Department Design in Low- and Middle-Income Settings: Lessons from a University Hospital in Haiti

Background:

Studies from high-income settings have demonstrated that emergency department (ED) design is closely related to operational success; however, no standards exist for ED design in low- and middle-income countries (LMICs).

Objective:

We present ED design recommendations for LMICs based on our experience designing and operating the ED at Hôpital Universitaire de Mirebalais (HUM), an academic hospital in central Haiti. We also propose an ideal prototype for similar settings based on these recommendations.

Methods:

As part of a quality improvement project to redesign the HUM ED, we collected feedback on the current design from key stakeholders to identify design features impacting quality and efficiency of care. Feedback was reviewed by the clinical and design teams and consensus reached on key lessons learned, from which the prototype was designed.

Findings and conclusions:

ED design in LMICs must balance construction costs, sustainability in the local context, and the impact of physical infrastructure on care delivery. From our analysis, we propose seven key recommendations: 1) Design the “front end” of the ED with waiting areas that meet the needs of LMICs and dedicated space for triage to strengthen care delivery and patient safety. 2) Determine ED size and bed capacity with an understanding of the local health system and disease burden, and ensure line-of-sight visibility for ill patients, given limited monitoring equipment. 3) Accommodate for limited supply chains by building storage spaces that can manage large volumes of supplies. 4) Prioritize a maintainable system that can provide reliable oxygen. 5) Ensure infection prevention and control, including isolation rooms, by utilizing simple and affordable ventilation systems. 6) Give consideration to security, privacy, and well-being of patients, families, and staff. 7) Site the ED strategically within the hospital. Our prototype incorporates these features and may serve as a model for other EDs in LMICs.

Comparison of disinfection performance of UVC-LED and conventional upper-room UVGI systems

We developed a novel, compact upper-room ultraviolet germicidal irradiation system with light-emitting diode sources (UR-UVGI-LED) to enhance the disinfection of bioaerosols in an enclosed room space. Its effectiveness was evaluated and compared with the conventional upper-room ultraviolet germicidal irradiation system with mercury vapor sources (UR-UVGI-MV). Escherichia coli, Serratia marcescens, and Staphylococcus epidermidis were atomized under the well-mixed condition and exposed to UR-UVGI-LED (or UR-UVGI-MV) device. The intensity output of the UR-UVGI-LED was also varied from 0% (no LED), 25%, 50% to 100% to further evaluate the UR-UVGI-LED disinfection effectiveness under different power levels. The decay rates for UR-UVGI-LED ranged from -0.1420 ± 0.04 min^-1 to -0.3331 ± 0.07 min^-1 for Escherichia coli, -0.1288 ± 0.01 min^-1 to -0.3583 ± 0.02 min^-1 for Serratia marcescens, and -0.0330 ± 0.01 min^-1 to -0.0487 ± 0.01 min^-1 for Staphylococcus epidermidis. It was noticed that the intensity level had a non-linear influence on the UR-UVGI-LED's performance. The decay rates achieved by the UR-UVGI-MV system were -0.3867 ± 0.08 min^-1 , -0.4745 ± 0.002 min^-1 , and -0.1624 ± 0.02 min^-1 for Escherichia coli, Serratia marcescens, and Staphylococcus epidermidis, respectively. Hence, the disinfection performance of both UR-UVGI-LED and UR-UVGI-MV systems was comparable for Escherichia coli and Serratia marcescens. These results demonstrate that the UR-UVGI-LED system has a high potential to be used as a safe and effective irradiated light source to disinfect indoor airborne pathogens.

Potential benefits and harms of the use of UV radiation in transmission of tuberculosis in South African health facilities

The incidence and prevalence of transmitted Mycobacterium tuberculosis have risen very rapidly in modern society. Environmental control measure such as ultraviolet radiation has been introduced in various health care facilities. This preventative measure has been extensively explored in the medical, legislative and public forums. However, the guidelines and manufacturer's claims have created controversies, in terms of prevention of cross-transmission of M. tuberculosis in health care facilities. In this article, the authors reviewed the overall benefits and harms associated with the use of ultraviolet radiation in the prevention of M. tuberculosis transmission. The author concluded that there are still existing gaps in proving beyond any reasonable doubt that ultraviolet radiations absolutely prevent the spread of M. tuberculosis in South African health facilities.

Reducing tuberculosis transmission: a consensus document from the World Health Organization Regional Office for Europe

Evidence-based guidance is needed on 1) how tuberculosis (TB) infectiousness evolves in response to effective treatment and 2) how the TB infection risk can be minimised to help countries to implement community-based, outpatient-based care.This document aims to 1) review the available evidence on how quickly TB infectiousness responds to effective treatment (and which factors can lower or boost infectiousness), 2) review policy options on the infectiousness of TB patients relevant to the World Health Organization European Region, 3) define limitations of the available evidence and 4) provide recommendations for further research.The consensus document aims to target all professionals dealing with TB (e.g TB specialists, pulmonologists, infectious disease specialists, primary healthcare professionals, and other clinical and public health professionals), as well as health staff working in settings where TB infection is prevalent.

Modeling the Airborne Infection Risk of Tuberculosis for a Research Facility in eMalahleni, South Africa

A detailed mathematical modeling framework for the risk of airborne infectious disease transmission in indoor spaces was developed to enable mathematical analysis of experiments conducted at the Airborne Infections Research (AIR) facility, eMalahleni, South Africa. A model was built using this framework to explore possible causes of why an experiment at the AIR facility did not produce expected results. The experiment was conducted at the AIR facility from August 31, 2015 to December 4, 2015, in which the efficacy of upper room germicidal ultraviolet (GUV) irradiation as an environmental control was tested. However, the experiment did not produce the expected outcome of having fewer infections in the test animal room than the control room. The simulation results indicate that dynamic effects, caused by switching the GUV lights, power outages, or introduction of new patients, did not result in the unexpected outcomes. However, a sensitivity analysis highlights that significant uncertainty exists with risk of transmission predictions based on current measurement practices, due to the reliance on large viable literature ranges for parameters.

A pilot study on the disinfection efficacy of localized UV on the flushing-generated spread of pathogens

The process of toilet-flushing can generate flushing-associated water droplets which can potentially expose humans to pathogen-laden aerosols. Very little is known about such aerosol dissemination or the means for minimizing exposure to these aerosols. This study has evaluated the efficacy of ultraviolet waveband C (UV-C) for disinfection of flushing-generated pathogen-laden aerosols through tests with localized disinfection systems for airborne and surface contaminations. Three types of bacteria were chosen for investigation: Staphylococcus epidermidis, Escherichia coli, and Salmonella typhimurium. Tests were conducted with UV-C tubes of 5 W and 10 W. High levels of disinfection efficacies were observed, ranging from 76% to 97% for bacteria-laden aerosols at sources of emission, and efficiencies of 53% to 79% for surface samples in localized systems. The results from the localized systems were further compared with those obtained with an upper-room ultraviolet germicidal irradiation (UVGI) system. As it is important to note, the UV-C doses and ozone emissions for the localized systems were found well below the limits recommended in current guidelines. This research has shown that the disinfection of flushing-generated pathogen-laden aerosols in proximity to the source of emission was more effective than at the more distant sites where aerosols may be dispersed to the environment.

Where is tuberculosis transmission happening? Insights from the literature, new tools to study transmission and implications for the elimination of tuberculosis

More than 10 million new cases of tuberculosis (TB) are diagnosed worldwide each year. The majority of these cases occur in low- and middle-income countries where the TB epidemic is predominantly driven by transmission. Efforts to 'end TB' will depend upon our ability to halt ongoing transmission. However, recent studies of new approaches to interrupt transmission have demonstrated inconsistent effects on reducing population-level TB incidence. TB transmission occurs across a wide range of settings, that include households and hospitals, but also community-based settings. While home-based contact investigations and infection control programmes in hospitals and clinics have a successful track record as TB control activities, there is a gap in our knowledge of where, and between whom, community-based transmission of TB occurs. Novel tools, including molecular epidemiology, geospatial analyses and ventilation studies, provide hope for improving our understanding of transmission in countries where the burden of TB is greatest. By integrating these diverse and innovative tools, we can enhance our ability to identify transmission events by documenting the opportunity for transmission-through either an epidemiologic or geospatial connection-alongside genomic evidence for transmission, based upon genetically similar TB strains. A greater understanding of locations and patterns of transmission will translate into meaningful improvements in our current TB control activities by informing targeted, evidence-based public health interventions.

Better than a pound of cure: preventing the development of multidrug-resistant tuberculosis

Diagnostic and treatment delays contribute to increased death and disability among the 490,000 adults and children who develop multidrug-resistant (MDR) tuberculosis every year. Since the treatment of MDR tuberculosis is complex, costly and often toxic, tuberculosis control programs should prioritize strategies to prevent drug-resistant tuberculosis. Opportunities to limit transmission and prevent disease progression in close contacts of MDR tuberculosis cases are often neglected. Effective MDR tuberculosis preventive strategies could minimize the costs for patients and healthcare systems. This review characterizes the biological basis for the development of MDR tuberculosis, outlines the evidence for strategies to reduce transmission and highlights programmatic approaches to the management of patients infected with drug-resistant strains of Mycobacterium tuberculosis.

Drug-Resistant tuberculosis - primary transmission and management

The DOTS strategy assisted global tuberculosis (TB) control, but was unable to prevent the emergence and spread of drug-resistant strains. Genomic evidence confirms the transmission of drug-resistant Mycobacterium tuberculosis strains in many different settings, indicative of epidemic spread. These findings emphasise the need for enhanced infection control measures in health care and congregate settings. Young children in TB endemic areas are particularly vulnerable. Although advances in TB drug and vaccine development are urgently needed, improved access to currently available preventive therapy and treatment for drug resistant TB could reduce the disease burden and adverse outcomes experienced by children. We review new insights into the transmission dynamics of drug resistant TB, the estimated disease burden in children and optimal management strategies to consider.

Designing and Evaluating Interventions to Halt the Transmission of Tuberculosis

To reduce the incidence of tuberculosis, it is insufficient to simply understand the dynamics of tuberculosis transmission. Rather, we must design and rigorously evaluate interventions to halt transmission, prioritizing those interventions most likely to achieve population-level impact. Synergy in reducing tuberculosis transmission may be attainable by combining interventions that shrink the reservoir of latent Mycobacterium tuberculosis infection (preventive therapy), shorten the time between disease onset and treatment initiation (case finding and diagnosis), and prevent transmission in key settings, such as the built environment (infection control). In evaluating efficacy and estimating population-level impact, cluster-randomized trials and mechanistic models play particularly prominent roles. Historical and contemporary evidence suggests that effective public health interventions can halt tuberculosis transmission, but an evidence-based approach based on knowledge of local epidemiology is necessary for success. We provide a roadmap for designing, evaluating, and modeling interventions to interrupt the process of transmission that fuels a diverse array of tuberculosis epidemics worldwide.

The epidemiology, pathogenesis, transmission, diagnosis, and management of multidrug-resistant, extensively drug-resistant, and incurable tuberculosis

Global tuberculosis incidence has declined marginally over the past decade, and tuberculosis remains out of control in several parts of the world including Africa and Asia. Although tuberculosis control has been effective in some regions of the world, these gains are threatened by the increasing burden of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis. XDR tuberculosis has evolved in several tuberculosis-endemic countries to drug-incurable or programmatically incurable tuberculosis (totally drug-resistant tuberculosis). This poses several challenges similar to those encountered in the pre-chemotherapy era, including the inability to cure tuberculosis, high mortality, and the need for alternative methods to prevent disease transmission. This phenomenon mirrors the worldwide increase in antimicrobial resistance and the emergence of other MDR pathogens, such as malaria, HIV, and Gram-negative bacteria. MDR and XDR tuberculosis are associated with high morbidity and substantial mortality, are a threat to health-care workers, prohibitively expensive to treat, and are therefore a serious public health problem. In this Commission, we examine several aspects of drug-resistant tuberculosis. The traditional view that acquired resistance to antituberculous drugs is driven by poor compliance and programmatic failure is now being questioned, and several lines of evidence suggest that alternative mechanisms-including pharmacokinetic variability, induction of efflux pumps that transport the drug out of cells, and suboptimal drug penetration into tuberculosis lesions-are likely crucial to the pathogenesis of drug-resistant tuberculosis. These factors have implications for the design of new interventions, drug delivery and dosing mechanisms, and public health policy. We discuss epidemiology and transmission dynamics, including new insights into the fundamental biology of transmission, and we review the utility of newer diagnostic tools, including molecular tests and next-generation whole-genome sequencing, and their potential for clinical effectiveness. Relevant research priorities are highlighted, including optimal medical and surgical management, the role of newer and repurposed drugs (including bedaquiline, delamanid, and linezolid), pharmacokinetic and pharmacodynamic considerations, preventive strategies (such as prophylaxis in MDR and XDR contacts), palliative and patient-orientated care aspects, and medicolegal and ethical issues.

Tuberculosis Infection Control in Health-Care Facilities: Environmental Control and Personal Protection

Transmission of tuberculosis (TB) is a recognized risk to patients and healthcare workers in healthcare settings. The literature review suggests that implementation of combination control measures reduces the risk of TB transmission. Guidelines suggest a three-level hierarchy of controls including administrative, environmental, and respiratory protection. Among environmental controls, installation of ventilation systems is a priority because ventilation reduces the number of infectious particles in the air. Natural ventilation is cost-effective but depends on climatic conditions. Supplemented intervention such as air-cleaning methods including high efficiency particulate air filtration and ultraviolet germicidal irradiation should be considered in areas where adequate ventilation is difficult to achieve. Personal protective equipment including particulate respirators provides additional benefit when administrative and environmental controls cannot assure protection.

Indoor environmental control of tuberculosis and other airborne infections

Tuberculosis (TB) remains the airborne infection of global importance, although many environmental interventions to control TB apply to influenza and other infections with airborne potential. This review focuses on the global problem and the current state of available environmental interventions. TB transmission is facilitated in overcrowded, poorly ventilated congregate settings, such as hospitals, clinics, prisons, jails, and refugee camps. The best means of TB transmission control is source control- to identify unsuspected infectious cases and to promptly begin effective therapy. However, even with active case finding and rapid diagnostics, not every unsuspected case will be identified, and environmental control measures remain the next intervention of choice. Natural ventilation is the main means of air disinfection and has the advantage of wide availability, low cost, and high efficacy-under optimal conditions. It is usually not applicable all year in colder climates and may not be effective when windows are closed on cold nights in warm climates, for security, and for pest control. In warm climates, windows may be closed when air conditioning is installed for thermal comfort. Although mechanical ventilation, if properly installed and maintained, can provide adequate air disinfection, it is expensive to install, maintain, and operate. The most cost-effective way to achieve high levels of air disinfection is upper room germicidal irradiation. The safe and effective application of this poorly defined intervention is now well understood, and recently published evidence-based application guidelines will make implementation easier.

The microbiome of the built environment and mental health

The microbiome of the built environment (MoBE) is a relatively new area of study. While some knowledge has been gained regarding impacts of the MoBE on the human microbiome and disease vulnerability, there is little knowledge of the impacts of the MoBE on mental health. Depending on the specific microbial species involved, the transfer of microorganisms from the built environment to occupant's cutaneous or mucosal membranes has the potential to increase or disrupt immunoregulation and/or exaggerate or suppress inflammation. Preclinical evidence highlighting the influence of the microbiota on systemic inflammation supports the assertion that microorganisms, including those originating from the built environment, have the potential to either increase or decrease the risk of inflammation-induced psychiatric conditions and their symptom severity. With advanced understanding of both the ecology of the built environment, and its influence on the human microbiome, it may be possible to develop bioinformed strategies for management of the built environment to promote mental health. Here we present a brief summary of microbiome research in both areas and highlight two interdependencies including the following: (1) effects of the MoBE on the human microbiome and (2) potential opportunities for manipulation of the MoBE in order to improve mental health. In addition, we propose future research directions including strategies for assessment of changes in the microbiome of common areas of built environments shared by multiple human occupants, and associated cohort-level changes in the mental health of those who spend time in the buildings. Overall, our understanding of the fields of both the MoBE and influence of host-associated microorganisms on mental health are advancing at a rapid pace and, if linked, could offer considerable benefit to health and wellness.