Improving natural ventilation in hospital waiting and consulting rooms to reduce nosocomial tuberculosis transmission risk in a low resource setting

Assessing ventilation through ambient carbon dioxide concentrations across multiple healthcare levels in Ghana

Infection prevention and control (IPC) measures safeguard primary healthcare systems, especially as the infectious disease landscape evolves due to climate and environmental change, increased global mobility, and vaccine hesitancy and inequity, which can introduce unexpected pathogens. This study explores the importance of an "always-on," low-cost IPC approach, focusing on the role of natural ventilation in health facilities, particularly in low-resource settings. Ambient carbon dioxide (CO2) levels are increasingly used as a measure of ventilation effectiveness allowing for spot checks and targeted ventilation improvements. Data were collected through purposive sampling in Northern Ghana over a three-month period. Levels of CO2 ppm (parts per million) were measured by a handheld device in various healthcare settings, including Community-Based Health Planning and Services (CHPS) facilities, municipal and teaching hospitals, and community settings to assess ventilation effectiveness. Analyses compared CO2 readings in community and hospital settings as well as in those settings with and without natural ventilation. A total of 40 facilities were evaluated in this study; 90% were healthcare facilities and 75% had natural ventilation (with an open window, door or wall). Facilities that relied on natural ventilation were mostly community health centers (60% vs 0%) and more commonly had patients present (83% vs 40%) compared with facilities without natural ventilation. Facilities with natural ventilation had significantly lower CO2 concentrations (CO2 ppm: 663 vs 1378, p = 0.0043) and were more likely to meet international thresholds of CO2 < 800 ppm (87% vs 10%, p = <0.0001) and CO2 < 1000 ppm (97% vs 20%, p = <0.0001). The adjusted odds ratio of low CO2 in the natural facilities compared with non-natural were: odds ratios, OR (95% CI): 21.7 (1.89, 247) for CO2 < 800 ppm, and 16.8 (1.55, 183) for CO2 < 1000 ppm. Natural ventilation in these facilities was consistently significantly associated with higher likelihood of low CO2 concentrations. Improved ventilation represents one cost-effective layer of IPC. This study highlights the continuing role natural ventilation can play in health facility design in community health care clinics. Most health facilities met standard CO2 thresholds, particularly in community health facilities. Further research is needed to optimize the use of natural ventilation. The use of a handheld devices to track a simple metric, CO2 levels, could improve appreciation of ventilation among healthcare workers and public health professionals and allow for them to target improvements. This study highlights potential lessons in the built environment of community primary health facilities as a blueprint for low-cost, integrated multi-layer IPC measures to mitigate respiratory illness and anticipate future outbreaks.

Investigating socio-ecological factors influencing implementation of tuberculosis infection prevention and control in rural Papua New Guinea

BACKGROUND

Tuberculosis (TB) is a highly transmissible infectious disease killing millions of people yearly, particularly in low-income countries. TB is most likely to be transmitted in healthcare settings with poor infection control practices. Implementing TB infection prevention and control (TB-IPC) is pivotal to preventing TB transmission in healthcare settings. This study investigated diverse stakeholders' perspectives relating to barriers and strategies for TB-IPC in rural hospitals in Papua New Guinea.

METHODS

Multiple qualitative case studies were conducted with 32 key stakeholders with experience in TB services. Data collection drew on three primary sources to triangulate data: semi-structured interviews, document reviews and field notes. The data were analyzed using hybrid deductive-inductive thematic analysis.

RESULTS

Our results reveal that key stakeholders perceive multiple interdependent factors that affect TB-IPC practice. The key emerging themes include strategic planning for and prioritizing TB-IPC guidelines; governance, leadership and accountability at the provincial level; community attitudes towards TB control; institutional capacity to deliver TB care, healthcare workers' safety, and long-term partnership and integration of TB-IPC programmes into the broad IPC programme.

CONCLUSIONS

The evidence suggests that a multi-perspective approach is crucial for TB-IPC guidelines in healthcare institutions. Interventions focusing on addressing health systems strengthening may improve the implementation of TB-IPC guidelines.

A comprehensive review of microbial contamination in the indoor environment: sources, sampling, health risks, and mitigation strategies

The quality of the indoor environment significantly impacts human health and productivity, especially given the amount of time individuals spend indoors globally. While chemical pollutants have been a focus of indoor air quality research, microbial contaminants also have a significant bearing on indoor air quality. This review provides a comprehensive overview of microbial contamination in built environments, covering sources, sampling strategies, and analysis methods. Microbial contamination has various origins, including human occupants, pets, and the outdoor environment. Sampling strategies for indoor microbial contamination include air, surface, and dust sampling, and various analysis methods are used to assess microbial diversity and complexity in indoor environments. The review also discusses the health risks associated with microbial contaminants, including bacteria, fungi, and viruses, and their products in indoor air, highlighting the need for evidence-based studies that can relate to specific health conditions. The importance of indoor air quality is emphasized from the perspective of the COVID-19 pandemic. A section of the review highlights the knowledge gap related to microbiological burden in indoor environments in developing countries, using India as a representative example. Finally, potential mitigation strategies to improve microbiological indoor air quality are briefly reviewed.

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.

Tuberculosis infection prevention and control in rural Papua New Guinea: an evaluation using the infection prevention and control assessment framework

BACKGROUND

Papua New Guinea (PNG) is one of the 14 countries categorised as having a triple burden of tuberculosis (TB), multidrug-resistant TB (MDR TB), and TB-human immunodeficiency virus (HIV) co-infections. TB infection prevention and control (TB-IPC) guidelines were introduced in 2011 by the National Health Department of PNG. This study assesses the implementation of this policy in a sample of district hospitals in two regions of PNG.

METHODS

The implementation of TB-IPC policy was assessed using a survey method based on the World Health Organization (WHO) IPC assessment framework (IPCAF) to implement the WHO's IPC core components. The study included facility assessment at ten district hospitals and validation observations of TB-IPC practices.

RESULTS

Overall, implementation of IPC and TB-IPC guidelines was inadequate in participating facilities. Though 80% of facilities had an IPC program, many needed more clearly defined IPC objectives, budget allocation, and yearly work plans. In addition, they did not include senior facility managers in the IPC committee. 80% (n = 8 of 10) of hospitals had no IPC training and education; 90% had no IPC committee to support the IPC team; 70% had no surveillance protocols to monitor infections, and only 20% used multimodal strategies for IPC activities. Similarly, 70% of facilities had a TB-IPC program without a proper budget and did not include facility managers in the TB-IPC team; 80% indicated that patient flow poses a risk of TB transmission; 70% had poor ventilation systems; 90% had inadequate isolation rooms; and though 80% have personal protective equipment available, frequent shortages were reported.

CONCLUSIONS

The WHO-recommended TB-IPC policy is not effectively implemented in most of the participating district hospitals. Improvements in implementing and disseminating TB-IPC guidelines, monitoring TB-IPC practices, and systematic healthcare worker training are essential to improve TB-IPC guidelines' operationalisation in health settings to reduce TB prevalence in PNG.

Holistic Approach to Enhance Airborne Infection Control Practices in Health Care Facilities Involved in the Management of Tuberculosis in a Metropolitan City in India - An Implementation Research

Background

Airborne infection control (AIC) is a less focused aspect of tuberculosis (TB) prevention. We describe AIC practices in primary health care centres, awareness and practices of AIC among health care providers (HCPs) and TB patients. We implemented a package of interventions to improve awareness and practices among them and assessed its impact.

Methodology

The study used a quasi-experimental study design. A semi-structured checklist was used for health facility assessment and a self-administered questionnaire of HCPs. Pre- and postintervention assessments were made in urban primary health centers (UPHCs), HCPs, and patients. Interventions included sharing facility-specific recommendations, AIC plans and guidelines, HCP training, and patient education. Statistical difference between the two time periods was assessed using the Chi-square test.

Results

A total of 23 and 25 UPHCs were included for pre- and postintervention assessments. All 25 centers participated in interventions. Open areas were >20% of ground area in all facilities. No AIC committee was present in any of the facilities at both pre- and postintervention. Of all HCPs, 7% (23/337) versus 65% (202/310) had undergone AIC training. Good awareness improved from 24% (81/337) to 71% (220/310) after intervention (P < 0.001). Appropriate cough hygiene was known to 20% (51/262) versus 58% (152/263) patients at two assessments (P < 0.001).

Conclusion

Comprehensive intervention, including supportive supervision of health centers, training of HCPs, and patient education, can improve AIC practices.

Airborne transmission of biological agents within the indoor built environment: a multidisciplinary review

The nature and airborne dispersion of the underestimated biological agents, monitoring, analysis and transmission among the human occupants into building environment is a major challenge of today. Those agents play a crucial role in ensuring comfortable, healthy and risk-free conditions into indoor working and leaving spaces. It is known that ventilation systems influence strongly the transmission of indoor air pollutants, with scarce information although to have been reported for biological agents until 2019. The biological agents' source release and the trajectory of airborne transmission are both important in terms of optimising the design of the heating, ventilation and air conditioning systems of the future. In addition, modelling via computational fluid dynamics (CFD) will become a more valuable tool in foreseeing risks and tackle hazards when pollutants and biological agents released into closed spaces. Promising results on the prediction of their dispersion routes and concentration levels, as well as the selection of the appropriate ventilation strategy, provide crucial information on risk minimisation of the airborne transmission among humans. Under this context, the present multidisciplinary review considers four interrelated aspects of the dispersion of biological agents in closed spaces, (a) the nature and airborne transmission route of the examined agents, (b) the biological origin and health effects of the major microbial pathogens on the human respiratory system, (c) the role of heating, ventilation and air-conditioning systems in the airborne transmission and (d) the associated computer modelling approaches. This adopted methodology allows the discussion of the existing findings, on-going research, identification of the main research gaps and future directions from a multidisciplinary point of view which will be helpful for substantial innovations in the field.

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.

Nursing Home Adoption of CDC and ASHRAE COVID-19 Built Environment Recommendations: A Characterization Study of Colorado Nursing Home Facilities

BACKGROUND

During the COVID-19 pandemic, the Centers for Disease Control and Prevention (CDC) and ASHRAE provided infection control recommendations for the built environments and ventilation systems of nursing homes (NHs). The level of adoption of the suggested strategies is unknown, as little information has been obtained from NHs identifying the strategies that were implemented.

OBJECTIVE

The primary goal of our study was to characterize the built environments of Colorado NHs during the COVID-19 pandemic to assess the level of adoption of CDC and ASHRAE recommendations. Our secondary goal was to identify opportunities and barriers that NHs face as they work to create health-protective built environments in the future.

METHOD

We used the Nursing Home Built Environment survey to obtain data related to three main categories of CDC and ASHRAE recommendation for Colorado NHs: Resident Isolation, Improved Indoor Air Quality, and Staff Separation/Support.

RESULTS

Key findings included: (1) On average, NHs had 34% of their beds located in single-occupancy rooms; (2) seven (9%) NHs had designated COVID-positive "neighborhoods"; (3) 14 (20%) NHs had common area ventilation systems that were utilizing filters with a minimum efficiency reporting value 13 rating, or higher.

CONCLUSION

Most Colorado NHs did not fully implement the COVID-19 built environment strategies recommended by CDC and ASHRAE. While there are barriers to the adoption of many of the strategies, there are also opportunities for immediate improvements that can support the health of vulnerable NH populations as we continue to see high rates of aerosolized infectious disease spread in NH facilities.

Importance of ventilation and occupancy to Mycobacterium tuberculosis transmission rates in congregate settings

BACKGROUND

Ventilation rates are a key determinant of the transmission rate of Mycobacterium tuberculosis and other airborne infections. Targeting infection prevention and control (IPC) interventions at locations where ventilation rates are low and occupancy high could be a highly effective intervention strategy. Despite this, few data are available on ventilation rates and occupancy in congregate locations in high tuberculosis burden settings.

METHODS

We collected carbon dioxide concentration and occupancy data in congregate locations and public transport on 88 occasions, in Cape Town, South Africa. For each location, we estimated ventilation rates and the relative rate of infection, accounting for ventilation rates and occupancy.

RESULTS

We show that the estimated potential transmission rate in congregate settings and public transport varies greatly between different settings. Overall, in the community we studied, estimated infection risk was higher in minibus taxis and trains than in salons, bars, and shops. Despite good levels of ventilation, infection risk could be high in the clinic due to high occupancy levels.

CONCLUSION

Public transport in particular may be promising targets for infection prevention and control interventions in this setting, both to reduce Mtb transmission, but also to reduce the transmission of other airborne pathogens such as measles and SARS-CoV-2.

Ventilation strategies and design impacts on indoor airborne transmission: A review

The COVID-19 outbreak has brought the indoor airborne transmission issue to the forefront. Although ventilation systems provide clean air and dilute indoor contaminated air, there is strong evidence that airborne transmission is the main route for contamination spread. This review paper aims to critically investigate ventilation impacts on particle spread and identify efficient ventilation strategies in controlling aerosol distribution in clinical and non-clinical environments. This article also examines influential ventilation design features (i.e., exhaust location) affecting ventilation performance in preventing aerosols spread. This paper shortlisted published documents for a review based on identification (keywords), pre-processing, screening, and eligibility of these articles. The literature review emphasizes the importance of ventilation systems' design and demonstrates all strategies (i.e., mechanical ventilation) could efficiently remove particles if appropriately designed. The study highlights the need for occupant-based ventilation systems, such as personalized ventilation instead of central systems, to reduce cross-infections. The literature underlines critical impacts of design features like ventilation rates and the number and location of exhausts and suggests designing systems considering airborne transmission. This review underpins that a higher ventilation rate should not be regarded as a sole indicator for designing ventilation systems because it cannot guarantee reducing risks. Using filtration and decontamination devices based on building functionalities and particle sizes can also increase ventilation performance. This paper suggests future research on optimizing ventilation systems, particularly in high infection risk spaces such as multi-storey hotel quarantine facilities. This review contributes to adjusting ventilation facilities to control indoor aerosol transmission.

Assessing impact of ventilation on airborne transmission of SARS-CoV-2: a cross-sectional analysis of naturally ventilated healthcare settings in Bangladesh

OBJECTIVES

To evaluate the risk of exposure to SARS-CoV-2 in naturally ventilated hospital settings by measuring parameters of ventilation and comparing these findings with results of bioaerosol sampling.

STUDY DESIGN

Cross-sectional study.

STUDY SETTING AND STUDY SAMPLE

The study sample included nine hospitals in Dhaka, Bangladesh. Ventilation characteristics and air samples were collected from 86 healthcare spaces during October 2020 to February 2021.

PRIMARY OUTCOME

Risk of cumulative SARS-CoV-2 infection by type of healthcare area.

SECONDARY OUTCOMES

Ventilation rates by healthcare space; risk of airborne detection of SARS-CoV-2 across healthcare spaces; impact of room characteristics on absolute ventilation; SARS-CoV-2 detection by naturally ventilated versus mechanically ventilated spaces.

RESULTS

The majority (78.7%) of naturally ventilated patient care rooms had ventilation rates that fell short of the recommended ventilation rate of 60 L/s/p. Using a modified Wells-Riley equation and local COVID-19 case numbers, we found that over a 40-hour exposure period, outpatient departments posed the highest median risk for infection (7.7%). SARS-CoV-2 RNA was most frequently detected in air samples from non-COVID wards (50.0%) followed by outpatient departments (42.9%). Naturally ventilated spaces (22.6%) had higher rates of SARS-CoV-2 detection compared with mechanically ventilated spaces (8.3%), though the difference was not statistically significant (p=0.128). In multivariable linear regression with calculated elasticity, open door area and cross-ventilation were found to have a significant impact on ventilation.

CONCLUSION

Our findings provide evidence that naturally ventilated healthcare settings may pose a high risk for exposure to SARS-CoV-2, particularly among non-COVID-designated spaces, but improving parameters of ventilation can mitigate this risk.

The Risk Status of Waiting Areas for Airborne Infection Control in Delhi Hospitals

Background

Hospital waiting areas are overlooked from the airborne infection control viewpoint as they are not classified as critical for infection control. This is the area where undiagnosed and potentially infected patients gather with susceptible and vulnerable patients, and there is no mechanism to segregate the two, especially when the potentially infected visitors/patients themselves are unaware of the infection or may be asymptomatic. It is important to know whether hospitals in Delhi, a populated, low-resource setting having community transmission/occurrence of airborne diseases such as tuberculosis, consider waiting areas as critical. Hence, this study aims to determine whether hospitals in Delhi consider waiting areas as critical areas from the airborne infection control viewpoint.

Methodology

The Right to Information Act, 2005, was used to request information from 11 hospitals included in this study.

Results

After compiling the results, it was found that five out of the 11 hospitals did not consider waiting areas as critical from the infection spread point of view. Two of the 11 hospitals acknowledged the criticality of waiting areas but did not include the same in the list of critical areas. Only three out of the 11 considered waiting areas as critical and included these in the list of critical areas in a hospital.

Conclusions

This study provided evidence that most hospitals in Delhi do not include waiting areas in the list of critical areas in a hospital.

Determinants of latent tuberculosis infection among nurses at public health centers in Indonesia

Background

The incidence of latent tuberculosis among healthcare workers, especially nurses, at public health centers in Indonesia has been increased. Therefore, factors related to the tuberculosis incidence need to be further investigated.

Objective

This study aimed to identify the determinants of latent tuberculosis infection among nurses at public health centers in Indonesia.

Methods

This non-experimental, cross-sectional study included 98 nurses. Data on the determinants of latent tuberculosis infection were collected using validated questionnaires, and the infection status was confirmed by Interferon Gamma Release Assay or IGRA test. Logistic regression was used for statistical analysis, with a significance level of p < 0.05.

Results

Health facilities for tuberculosis transmission prevention were available in all public health centers (100%). Protocols for preventing tuberculosis transmission including occupational health and safety training (OR = 13.24, 95% CI [2.29-58.55]; p = 0.001), handwashing after contact with patients or specimens (OR = 20.55, 95% CI [4.23-99.93]; p = 0.000), and wearing of medical masks (OR = 9.56, 95% CI [1.99-45.69]; p = 0.005) were found to be significant determinants of latent tuberculosis infection among nurses.

Conclusion

The availability of protective equipment and implementation of health protocols among nurses at public health centers are the main determinants of latent tuberculosis infection. Hence, they should be maintained by all nurses to prevent the spread of tuberculosis.

Preparedness of tertiary care hospitals to implement the national TB infection prevention and control guidelines in Bangladesh: A qualitative exploration

In high tuberculosis (TB) burden countries, health settings, including non-designated TB hospitals, host many patients with pulmonary TB. Bangladesh's National TB Control Program aims to strengthen TB infection prevention and control (IPC) in health settings. However, there has been no published literature to date that assessed the preparedness of hospitals to comply with the recommendations. To address this gap, our study examined healthcare workers knowledge and attitudes towards TB IPC guidelines and their perceptions regarding the hospitals' preparedness in Bangladesh. Between January to December 2019, we conducted 16 key-informant interviews and four focus group discussions with healthcare workers from two public tertiary care hospitals. In addition, we undertook a review of 13 documents [i.e., hospital policy, annual report, staff list, published manuscript]. Our findings showed that healthcare workers acknowledged the TB risk and were willing to implement the TB IPC measures but identified key barriers impacting implementation. Gaps were identified in: policy (no TB policy or guidelines in the hospital), health systems (healthcare workers were unaware of the guidelines, lack of TB IPC program, training and education, absence of healthcare-associated TB infection surveillance, low priority of TB IPC, no TB IPC monitoring and feedback, high patient load and bed occupancy, and limited supply of IPC resources) and behavioural factors (risk perception, compliance, and self and social stigma). The additional service-level gap was the lack of electronic medical record systems. These findings highlighted that while there is a demand amongst healthcare workers to implement TB IPC measures, the public tertiary care hospitals have got key issues to address. Therefore, the National TB Control Program may consider these gaps, provide TB IPC guidelines to these hospitals, assist them in developing hospital-level IPC manual, provide training, and coordinate with the ministry of health to allocate separate budget, staffing, and IPC resources to implement the control measures successfully.

Examining pulmonary TB patient management and healthcare workers exposures in two public tertiary care hospitals, Bangladesh

Implementation of tuberculosis (TB) infection prevention and control (IPC) guidelines in public tertiary care general hospitals remain challenging due to limited evidence of pulmonary TB (PTB) patients' duration of hospital stay and management. To fill this evidence gap, this study examined adult PTB patient management, healthcare workers' (HCWs) exposures and IPC practices in two public tertiary care hospitals in Bangladesh.Between December 2017 and September 2019, a multidisciplinary team conducted structured observations, a hospital record review, and in-depth interviews with hospital staff from four adult medicine wards.Over 20 months, we identified 1,200 presumptive TB patients through the hospital record review, of whom 263 were confirmed PTB patients who stayed in the hospital, a median of 4.7 days without TB treatment and possibly contaminated the inpatients wards. Over 141 observation hours, we found a median of 3.35 occupants present per 10 m2 of floor space and recorded a total of 17,085 coughs and 316 sneezes: a median of 3.9 coughs or sneezes per 10 m2 per hour per ward. Only 8.4% of coughs and 21% of sneezes were covered by cloths, paper, tissues, or by hand. The HCWs reportedly could not isolate the TB patients due to limited resources and space and could not provide them with a mask. Further, patients and HCWs did not wear any respirators.The study identified that most TB patients stayed in the hospitals untreated for some duration of time. These PTB patients frequently coughed and sneezed without any facial protection that potentially contaminated the ward environment and put everyone, including the HCWs, at risk of TB infection. Interventions that target TB patients screening on admission, isolation of presumptive TB patients, respiratory hygiene, and HCWs' use of personal protective equipment need to be enhanced and evaluated for acceptability, practicality and scale-up.

Factors affecting aerosol SARS-CoV-2 transmission via HVAC systems; a modeling study

The role of heating, ventilation, and air-conditioning (HVAC) systems in the transmission of SARS-CoV-2 is unclear. To address this gap, we simulated the release of SARS-CoV-2 in a multistory office building and three social gathering settings (bar/restaurant, nightclub, wedding venue) using a well-mixed, multi-zone building model similar to those used by Wells, Riley, and others. We varied key factors of HVAC systems, such as the Air Changes Per Hour rate (ACH), Fraction of Outside Air (FOA), and Minimum Efficiency Reporting Values (MERV) to examine their effect on viral transmission, and additionally simulated the protective effects of in-unit ultraviolet light decontamination (UVC) and separate in-room air filtration. In all building types, increasing the ACH reduced simulated infections, and the effects were seen even with low aerosol emission rates. However, the benefits of increasing the fraction of outside air and filter efficiency rating were greatest when the aerosol emission rate was high. UVC filtration improved the performance of typical HVAC systems. In-room filtration in an office setting similarly reduced overall infections but worked better when placed in every room. Overall, we found little evidence that HVAC systems facilitate SARS-CoV-2 transmission; most infections in the simulated office occurred near the emission source, with some infections in individuals temporarily visiting the release zone. HVAC systems only increased infections in one scenario involving a marginal increase in airflow in a poorly ventilated space, which slightly increased the likelihood of transmission outside the release zone. We found that improving air circulation rates, increasing filter MERV rating, increasing the fraction of outside air, and applying UVC radiation and in-room filtration may reduce SARS-CoV-2 transmission indoors. However, these mitigation measures are unlikely to provide a protective benefit unless SARS-CoV-2 aerosol emission rates are high (>1,000 Plaque-forming units (PFU) / min).

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.

Reducing the risk of tuberculosis transmission for HCWs in high incidence settings

Globally, tuberculosis (TB) is a leading cause of death from a single infectious agent. Healthcare workers (HCWs) are at increased risk of hospital-acquired TB infection due to persistent exposure to Mycobacterium tuberculosis (Mtb) in healthcare settings. The World Health Organization (WHO) has developed an international system of infection prevention and control (IPC) interventions to interrupt the cycle of nosocomial TB transmission. The guidelines on TB IPC have proposed a comprehensive hierarchy of three core practices, comprising: administrative controls, environmental controls, and personal respiratory protection. However, the implementation of most recommendations goes beyond minimal physical and organisational requirements and thus cannot be appropriately introduced in resource-constrained settings and areas of high TB incidence. In many low- and middle-income countries (LMICs) the lack of knowledge, expertise and practice on TB IPC is a major barrier to the implementation of essential interventions. HCWs often underestimate the risk of airborne Mtb dissemination during tidal breathing. The lack of required expertise and funding to design, install and maintain the environmental control systems can lead to inadequate dilution of infectious particles in the air, and in turn, increase the risk of TB dissemination. Insufficient supply of particulate respirators and lack of direction on the re-use of respiratory protection is associated with unsafe working practices and increased risk of TB transmission between patients and HCWs. Delayed diagnosis and initiation of treatment are commonly influenced by the effectiveness of healthcare systems to identify TB patients, and the availability of rapid molecular diagnostic tools. Failure to recognise resistance to first-line drugs contributes to the emergence of drug-resistant Mtb strains, including multidrug-resistant and extensively drug-resistant Mtb. Future guideline development must consider the social, economic, cultural and climatic conditions to ensure that recommended control measures can be implemented in not only high-income countries, but more importantly low-income, high TB burden settings. Urgent action and more ambitious investments are needed at both regional and national levels to get back on track to reach the global TB targets, especially in the context of the COVID-19 pandemic.

Ventilation and air-conditioning systems in dental clinics and COVID-19: How much do we know?

Background

This study evaluated the association between knowledge and management of ventilation and air-conditioning systems (VAC) to avoid the spread of the SARS-CoV-2 virus in health facilities by dentists and demographic variables.

Material and Methods

A cross-sectional digital media survey was administered to dentists as part of global research. The core questionnaire was used including four additional questions on VAC (Q1: knowledge, Q2: work settings, Q3: temperature, and Q4: maintenance). A descriptive analysis was conducted for sociodemographic and VAC variables, and bivariate analysis was carried out using different tests.

Results

5370 dentists answered the survey (median age of 45 years; 72.22% women). About half of the respondents said that they knew about the guidelines issued for the management of air conditioners (AC) during the pandemic, and 16.77% have made modifications to their VAC systems during this period. The most frequent AC temperature range used in the dentists’ offices during the pandemic was 18°C to 20°C. As age increased, self-reported knowledge about VAC guidelines expanded. Remote and rural regions were perceived to have less knowledge of the guidelines.

Conclusions

Although perceptions of knowledge about VAC systems during the COVID-19 pandemic was high, the temperature in dental offices was colder than that recommended. Greater disclosure of VAC management practices and adherence to VAC management guidelines are required.

Key words:Air conditioning, dentistry, coronavirus.

Estimating ventilation rates in rooms with varying occupancy levels: Relevance for reducing transmission risk of airborne pathogens

BACKGROUND

In light of the role that airborne transmission plays in the spread of SARS-CoV-2, as well as the ongoing high global mortality from well-known airborne diseases such as tuberculosis and measles, there is an urgent need for practical ways of identifying congregate spaces where low ventilation levels contribute to high transmission risk. Poorly ventilated clinic spaces in particular may be high risk, due to the presence of both infectious and susceptible people. While relatively simple approaches to estimating ventilation rates exist, the approaches most frequently used in epidemiology cannot be used where occupancy varies, and so cannot be reliably applied in many of the types of spaces where they are most needed.

METHODS

The aim of this study was to demonstrate the use of a non-steady state method to estimate the absolute ventilation rate, which can be applied in rooms where occupancy levels vary. We used data from a room in a primary healthcare clinic in a high TB and HIV prevalence setting, comprising indoor and outdoor carbon dioxide measurements and head counts (by age), taken over time. Two approaches were compared: approach 1 using a simple linear regression model and approach 2 using an ordinary differential equation model.

RESULTS

The absolute ventilation rate, Q, using approach 1 was 2407 l/s [95% CI: 1632-3181] and Q from approach 2 was 2743 l/s [95% CI: 2139-4429].

CONCLUSIONS

We demonstrate two methods that can be used to estimate ventilation rate in busy congregate settings, such as clinic waiting rooms. Both approaches produced comparable results, however the simple linear regression method has the advantage of not requiring room volume measurements. These methods can be used to identify poorly-ventilated spaces, allowing measures to be taken to reduce the airborne transmission of pathogens such as Mycobacterium tuberculosis, measles, and SARS-CoV-2.

Infection control in dental health care during and after the SARS-CoV-2 outbreak

COVID-19 is an emerging infectious disease caused by the widespread transmission of the coronavirus SARS-CoV-2. Some of those infected become seriously ill. Others do not show any symptoms, but can still contribute to transmission of the virus. SARS-CoV-2 is excreted in the oral cavity and can be spread via aerosols. Aerosol generating procedures in dental health care can increase the risk of transmission of the virus. Due to the risk of infection of both dental healthcare workers and patients, additional infection control measures for all patients are strongly recommended when providing dental health care. Consideration should be given to which infection control measures are necessary when providing care in both the current situation and in the future.

The Profile of the Patients with Double Infection HIV and TB in South West of Romania

Background: Co-infection with human immunodeficiency virus (HIV) / tuberculosis (TB) raises important diagnostic and treatment problems as the lung is one of the target organs for HIV. Studies have shown that an HIV patient is 5-15 times more likely to switch from Koch's bacillus-infected status to active tuberculosis. Material and method: Retrospective study on 207 patients with HIV/TB coinfection in the Oltenia area registered in the Regional Center for Monitoring and Evaluation of HIV/AIDS infection in Craiova to define the profile of patients with double TB-HIV infection in southern Romania for cases registered between 2005-2015. Results: 53.14% of patients were females. Most cases were from rural areas (56.10%) Half of them are born between 1988 and 1990 but only 5% graduated university. 66.18% don’t have a job and are supported by state with a monthly minimum income. 29.4% are smokers. More than 60% of cases had pulmonary TB and other 25% had concomitant pulmonary and extrapulmonary TB. TB and HIV have been diagnosed almost at the same time in 25% of cases. At the time of TB diagnosis 75% of patients had CD4+lymphocytes count <200cel/ml. We also noticed the absence of prophylaxis for TB in patients infected with HIV (PIH) and high incidence of hepatitis B (30.43%). Conclusions: Clinical expression, radiological and bacteriological aspects are often atypical in HIV/TB coinfected patients. The lack of TB prophylaxis and TB endemicity in the studied area may justify the large number of TB cases in HIV-infected patients.

Reducing the risk of infection to patients and staff during gynaecological outpatient and ambulatory appointments

This chapter explores ways to reduce the risk of severe acute respiratory syndrome coronavirus-2 transmission to women and staff within gynaecology outpatient clinics. The likely routes of transmission are discussed, namely through droplets, aerosols and fomites. Using the 'hierarchy of control' categories, elimination, substitution, engineering, administration and personal protective equipment, practical strategies for modifying virus exposure are presented. The management of specific clinical conditions are reviewed based on advice prepared by the specialist societies in conjunction with each other and the Royal College of Obstetricians and Gynaecologists. The need to maintain at least a minimal level of gynaecological services is recognised and that this should provide safe, equitable and effective care. Ways to reduce clinic attendance are discussed with the substitution of face-to-face with remote consultations and when this is relevant. Current recommendations for ambulatory procedures, which include colposcopy and hysteroscopy, are considered so that best use is made of reduced resources.

Self-contained system for mitigation of contaminated aerosol sources of SARS-CoV-2

Contaminated aerosols and micro droplets are easily generated by infected hosts through sneezing, coughing, speaking and breathing1-3 and harm humans' health and the global economy. While most of the efforts are usually targeted towards protecting individuals from getting infected,4 eliminating transmissions from infection sources is also important to prevent disease transmission. Supportive therapies for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV-2) pneumonia such as oxygen supplementation, nebulizers and non-invasive mechanical ventilation all carry an increased risk for viral transmission via aerosol to healthcare workers.5-9 In this work, we study the efficacy of five methods for self-containing aerosols emitted from infected subjects undergoing nebulization therapies with a diverse spectrum on oxygen delivery therapies. The work includes five study cases: Case I: Use of a Full-Face Mask with biofilter in bilevel positive airway pressure device (BPAP) therapy, Case II: Use of surgical mask in High Flow Nasal Cannula (HFNC) therapy, Case III: Use of a modified silicone disposable mask in a HFNC therapy, Case IV: Use of a modified silicone disposable mask with a regular nebulizer and normal breathing, Case V: Use of a mitigation box with biofilter in a Non-Invasive Positive Pressure Ventilator (NIPPV). We demonstrate that while cases I, III and IV showed efficacies of 98-100%; cases II and V, which are the most commonly used, resulted with significantly lower efficacies of 10-24% to mitigate the dispersion of nebulization aerosols. Therefore, implementing cases I, III and IV in health care facilities may help battle the contaminations and infections via aerosol transmission during a pandemic.

Engineering Solutions for Preventing Airborne Transmission in Hospitals with Resource Limitation and Demand Surge

Among the various strategies for the prevention of airborne transmission, engineering measures are placed high in the hierarchy of control. Modern hospitals in high-income countries have mechanical systems of building ventilation also called HVAC (heating, ventilation, and air-conditioning) but installation and maintenance of such systems is a challenging and resource-intensive task. Even when the state-of-the-art technology was used to build airborne infection isolation rooms (AIIRs), recommended standards were often not met in field studies. The current coronavirus disease-2019 pandemic has highlighted the need to find cost-effective and less resource-intensive engineering solutions. Moreover, there is a need for the involvement of interdisciplinary teams to find innovative infection control solutions and doctors are frequently lacking in their understanding of building ventilation-related problems as well as their possible solutions. The current article describes building ventilation strategies (natural ventilation and hybrid ventilation) for hospitals where HVAC systems are either lacking or do not meet the recommended standards. Other measures like the use of portable air cleaning technologies and temporary negative-pressure rooms can be used as supplementary strategies in situations of demand surge. It can be easily understood that thermal comfort is compromised in buildings that are not mechanically fitted with HVAC systems, therefore the given building ventilation strategies are more helpful when climatic conditions are moderate or other measures are combined to maintain thermal comfort.

Pragmatic Recommendations for Safety while Caring for Hospitalized Patients with COVID-19 in Low- and Middle-Income Countries

Infection prevention and control measures to control the spread of COVID-19 are challenging to implement in many low- and middle-income countries (LMICs). This is compounded by the fact that most recommendations are based on evidence that mainly originates in high-income countries. There are often availability, affordability, and feasibility barriers to applying such recommendations in LMICs, and therefore, there is a need for developing recommendations that are achievable in LMICs. We used a modified version of the GRADE method to select important questions, searched the literature for relevant evidence, and formulated pragmatic recommendations for safety while caring for patients with COVID-19 in LMICs. We selected five questions related to safety, covering minimal requirements for personal protective equipment (PPE), recommendations for extended use and reuse of PPE, restriction on the number of times healthcare workers enter patients' rooms, hand hygiene, and environmental ventilation. We formulated 21 recommendations that are feasible and affordable in LMICs.

Architectural design strategies for infection prevention and control (IPC) in health-care facilities: towards curbing the spread of Covid-19

Background

Sustainable design strategies are targeted at finding architectural solutions that reassure the well-being and coexistence of inorganic features, living organisms, and humans that make up the ecosystem. The emergence of the novel coronavirus, an increase in microbial resistance, and lack of a vaccine for the present pandemic have made it imperative to appraise the preventive strategies employed during the pre-antibiotic period. Sustainable architecture for children's hospital design and childcare facilities, apart from low energy and carbon emission, must integrate design strategies to confront the impact of infectious diseases.

Aim

The aim of the paper is to identify how the space patients and health-care workers0 occupy can be made safer from an architectural design perspective with the view of developing guidelines for policymakers and highlighting the architect's role in combating the pandemic.

Objectives

The objectives include; to examine the evolution of medical architecture and the nexus between infectious diseases and architectural space and suggest a design approach that enhances infection prevention and control (IPC).

Method

The paper relied on existing literature, interviews, and interactions with healthcare workers.

Results/Conclusion

The findings showed that design strategies have always played a significant role in infection prevention and control (IPC) and could as well be a panacea for curbing the spread of Covid -19.

Aerosol Transmission of SARS-CoV-2: Physical Principles and Implications

Evidence has emerged that SARS-CoV-2, the coronavirus that causes COVID-19, can be transmitted airborne in aerosol particles as well as in larger droplets or by surface deposits. This minireview outlines the underlying aerosol science, making links to aerosol research in other disciplines. SARS-CoV-2 is emitted in aerosol form during normal breathing by both asymptomatic and symptomatic people, remaining viable with a half-life of up to about an hour during which air movement can carry it considerable distances, although it simultaneously disperses. The proportion of the droplet size distribution within the aerosol range depends on the sites of origin within the respiratory tract and on whether the distribution is presented on a number or volume basis. Evaporation and fragmentation reduce the size of the droplets, whereas coalescence increases the mean droplet size. Aerosol particles containing SARS-CoV-2 can also coalesce with pollution particulates, and infection rates correlate with pollution. The operation of ventilation systems in public buildings and transportation can create infection hazards via aerosols, but provides opportunities for reducing the risk of transmission in ways as simple as switching from recirculated to outside air. There are also opportunities to inactivate SARS-CoV-2 in aerosol form with sunlight or UV lamps. The efficiency of masks for blocking aerosol transmission depends strongly on how well they fit. Research areas that urgently need further experimentation include the basis for variation in droplet size distribution and viral load, including droplets emitted by "superspreader" individuals; the evolution of droplet sizes after emission, their interaction with pollutant aerosols and their dispersal by turbulence, which gives a different basis for social distancing.

Healthcare Worker's Knowledge, Attitude, and Practice of Proper Face Mask Utilization, and Associated Factors in Police Health Facilities of Addis Ababa, Ethiopia

Background

Face masks were considered as an effective method of preventing respiratory infections like coronavirus infection. Identifying knowledge, attitude, and practice of healthcare workers regarding face mask utilization is very important to identify gaps and intervene immediately to control the spread of the infection. Hence, the main aim of this study was to determine the health worker’s knowledge, attitude, and practice of proper face mask utilization and associated factors at police health faculties in Addis Ababa, Ethiopia, 2020.

Methods

Across-sectional, quantitative approach study was conducted from June to July 2020. The study covered 408 health professionals of all categories working in the different police health facilities found in Addis Ababa, Ethiopia, during the study period. Data were collected using a pre-tested self-administered questionnaire adopted from different studies after getting consent from the study participants. After the data were collected, it was entered and analyzed using SPSS version 23 computer software. A logistic regression model was used to measure the association between the predictor and outcome variables. Statistical significance was declared at p-value<0.05. Direction and strength of association were expressed using OR and 95% CI.

Results

The study showed that the overall knowledge, attitude, and practice of the healthcare provider towards proper face mask utilization were 98 (33.5%), 185 (45.3%), and 272 (33.3%) respectively. Factors associated with proper utilization of face mask were educational status (AOR = 10.4, 95% CI: 2.51, 43.32), police rank (AOR=0.2. CI: 0.05, 0.41), profession (AOR = 7.7, 95% CI: 2.63, 22.65), and knowledge about face mask use (AOR = 0.01, 95% CI: 0.003, 0.023).

Conclusion

In this study, the level of knowledge and attitude towards face mask utilization was relatively low, and the level of proper face mask utilization was quite low in comparison with some studies. Comprehensive training about a face mask that focuses on its proper use should be designed and given by the authorities to healthcare workers who are on the front-line in the fight against COVID-19.

Interventions to reduce contaminated aerosols produced during dental procedures for preventing infectious diseases

BACKGROUND

Many dental procedures produce aerosols (droplets, droplet nuclei and splatter) that harbour various pathogenic micro-organisms and may pose a risk for the spread of infections between dentist and patient. The COVID-19 pandemic has led to greater concern about this risk.

OBJECTIVES

To assess the effectiveness of methods used during dental treatment procedures to minimize aerosol production and reduce or neutralize contamination in aerosols.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases on 17 September 2020: Cochrane Oral Health's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (in the Cochrane Library, 2020, Issue 8), MEDLINE Ovid (from 1946); Embase Ovid (from 1980); the WHO COVID-19 Global literature on coronavirus disease; the US National Institutes of Health Trials Registry (ClinicalTrials.gov); and the Cochrane COVID-19 Study Register. We placed no restrictions on the language or date of publication.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and controlled clinical trials (CCTs) on aerosol-generating procedures (AGPs) performed by dental healthcare providers that evaluated methods to reduce contaminated aerosols in dental clinics (excluding preprocedural mouthrinses). The primary outcomes were incidence of infection in dental staff or patients, and reduction in volume and level of contaminated aerosols in the operative environment. The secondary outcomes were cost, accessibility and feasibility.

DATA COLLECTION AND ANALYSIS

Two review authors screened search results, extracted data from the included studies, assessed the risk of bias in the studies, and judged the certainty of the available evidence. We used mean differences (MDs) and 95% confidence intervals (CIs) as the effect estimate for continuous outcomes, and random-effects meta-analysis to combine data. We assessed heterogeneity.

MAIN RESULTS

We included 16 studies with 425 participants aged 5 to 69 years. Eight studies had high risk of bias; eight had unclear risk of bias. No studies measured infection. All studies measured bacterial contamination using the surrogate outcome of colony-forming units (CFU). Two studies measured contamination per volume of air sampled at different distances from the patient's mouth, and 14 studies sampled particles on agar plates at specific distances from the patient's mouth. The results presented below should be interpreted with caution as the evidence is very low certainty due to heterogeneity, risk of bias, small sample sizes and wide confidence intervals. Moreover, we do not know the 'minimal clinically important difference' in CFU. High-volume evacuator Use of a high-volume evacuator (HVE) may reduce bacterial contamination in aerosols less than one foot (~ 30 cm) from a patient's mouth (MD -47.41, 95% CI -92.76 to -2.06; 3 RCTs, 122 participants (two studies had split-mouth design); very high heterogeneity I² = 95%), but not at longer distances (MD -1.00, -2.56 to 0.56; 1 RCT, 80 participants). One split-mouth RCT (six participants) found that HVE may not be more effective than conventional dental suction (saliva ejector or low-volume evacuator) at 40 cm (MD CFU -2.30, 95% CI -5.32 to 0.72) or 150 cm (MD -2.20, 95% CI -14.01 to 9.61). Dental isolation combination system One RCT (50 participants) found that there may be no difference in CFU between a combination system (Isolite) and a saliva ejector (low-volume evacuator) during AGPs (MD -0.31, 95% CI -0.82 to 0.20) or after AGPs (MD -0.35, -0.99 to 0.29). However, an 'n of 1' design study showed that the combination system may reduce CFU compared with rubber dam plus HVE (MD -125.20, 95% CI -174.02 to -76.38) or HVE (MD -109.30, 95% CI -153.01 to -65.59). Rubber dam One split-mouth RCT (10 participants) receiving dental treatment, found that there may be a reduction in CFU with rubber dam at one-metre (MD -16.20, 95% CI -19.36 to -13.04) and two-metre distance (MD -11.70, 95% CI -15.82 to -7.58). One RCT of 47 dental students found use of rubber dam may make no difference in CFU at the forehead (MD 0.98, 95% CI -0.73 to 2.70) and occipital region of the operator (MD 0.77, 95% CI -0.46 to 2.00). One split-mouth RCT (21 participants) found that rubber dam plus HVE may reduce CFU more than cotton roll plus HVE on the patient's chest (MD -251.00, 95% CI -267.95 to -234.05) and dental unit light (MD -12.70, 95% CI -12.85 to -12.55). Air cleaning systems One split-mouth CCT (two participants) used a local stand-alone air cleaning system (ACS), which may reduce aerosol contamination during cavity preparation (MD -66.70 CFU, 95% CI -120.15 to -13.25 per cubic metre) or ultrasonic scaling (MD -32.40, 95% CI - 51.55 to -13.25). Another CCT (50 participants) found that laminar flow in the dental clinic combined with a HEPA filter may reduce contamination approximately 76 cm from the floor (MD -483.56 CFU, 95% CI -550.02 to -417.10 per cubic feet per minute per patient) and 20 cm to 30 cm from the patient's mouth (MD -319.14 CFU, 95% CI - 385.60 to -252.68). Disinfectants ‒ antimicrobial coolants Two RCTs evaluated use of antimicrobial coolants during ultrasonic scaling. Compared with distilled water, coolant containing chlorhexidine (CHX), cinnamon extract coolant or povidone iodine may reduce CFU: CHX (MD -124.00, 95% CI -135.78 to -112.22; 20 participants), povidone iodine (MD -656.45, 95% CI -672.74 to -640.16; 40 participants), cinnamon (MD -644.55, 95% CI -668.70 to -620.40; 40 participants). CHX coolant may reduce CFU more than povidone iodine (MD -59.30, 95% CI -64.16 to -54.44; 20 participants), but not more than cinnamon extract (MD -11.90, 95% CI -35.88 to 12.08; 40 participants).

AUTHORS' CONCLUSIONS

We found no studies that evaluated disease transmission via aerosols in a dental setting; and no evidence about viral contamination in aerosols. All of the included studies measured bacterial contamination using colony-forming units. There appeared to be some benefit from the interventions evaluated but the available evidence is very low certainty so we are unable to draw reliable conclusions. We did not find any studies on methods such as ventilation, ionization, ozonisation, UV light and fogging. Studies are needed that measure contamination in aerosols, size distribution of aerosols and infection transmission risk for respiratory diseases such as COVID-19 in dental patients and staff.

Displacement ventilation: a viable ventilation strategy for makeshift hospitals and public buildings to contain COVID-19 and other airborne diseases

The SARS-CoV-2 virus has so far infected more than 31 million people around the world, and its impact is being felt by all. Patients with diseases such as COVID-19 should ideally be treated in negative pressure isolation rooms. However, due to the overwhelming demand for hospital beds, patients have been treated in general wards, hospital corridors and makeshift hospitals. Adequate building ventilation in hospitals and public spaces is a crucial factor to contain the disease (Escombe et al. 2007 PLoS Med. 4; Escombe et al. 2019 BMC Infect. Dis. 19, 88 (doi:10.1186/s12879-019-3717-9); Morawska & Milton 2020 Clin. Infect. Dis. ciaa939. (doi:10.1093/cid/ciaa939)), to exit lockdown safely, and reduce the chance of subsequent waves of outbreaks. A recently reported air-conditioner-induced COVID-19 outbreak caused by an asymptomatic patient, in a restaurant in Guangzhou, China (Lu et al. 2020 Emerg. Infect. Dis. 26) exposes our vulnerability to future outbreaks linked to ventilation in public spaces. We argue that displacement ventilation (either mechanical or natural ventilation), where air intakes are at low level and extracts are at high level, is a viable alternative to negative pressure isolation rooms, which are often not available on site in hospital wards and makeshift hospitals. Displacement ventilation produces negative pressure at the occupant level, which draws fresh air from outdoors, and positive pressure near the ceiling, which expels the hot and contaminated air out. We acknowledge that, in both developed and developing countries, many modern large structures lack the openings required for natural ventilation. This lack of openings can be supplemented by installing extract fans. We have also discussed and addressed the issue of the 'lock-up effect'. We provide guidelines for such mechanically assisted, naturally ventilated makeshift hospitals.

Airborne route and bad use of ventilation systems as non-negligible factors in SARS-CoV-2 transmission

The world is facing a pandemic of unseen proportions caused by a corona virus named SARS-CoV-2 with unprecedent worldwide measures being taken to tackle its contagion. Person-to-person transmission is accepted but WHO only considers aerosol transmission when procedures or support treatments that produce aerosol are performed. Transmission mechanisms are not fully understood and there is evidence for an airborne route to be considered, as the virus remains viable in aerosols for at least 3 h and that mask usage was the best intervention to prevent infection. Heating, Ventilation and Air Conditioning Systems (HVAC) are used as a primary infection disease control measure. However, if not correctly used, they may contribute to the transmission/spreading of airborne diseases as proposed in the past for SARS. The authors believe that airborne transmission is possible and that HVAC systems when not adequately used may contribute to the transmission of the virus, as suggested by descriptions from Japan, Germany, and the Diamond Princess Cruise Ship. Previous SARS outbreaks reported at Amoy Gardens, Emergency Rooms and Hotels, also suggested an airborne transmission. Further studies are warranted to confirm our hypotheses but the assumption of such way of transmission would cause a major shift in measures recommended to prevent infection such as the disseminated use of masks and structural changes to hospital and other facilities with HVAC systems.

Modeling of the Transmission of Coronaviruses, Measles Virus, Influenza Virus, Mycobacterium tuberculosis, and Legionella pneumophila in Dental Clinics

Dental health care workers are in close contact to their patients and are therefore at higher risk for contracting airborne infectious diseases. The transmission rates of airborne pathogens from patient to dental health care workers are unknown. With the outbreaks of infectious diseases, such as seasonal influenza, occasional outbreaks of measles and tuberculosis, and the current pandemic of the coronavirus disease COVID-19, it is important to estimate the risks for dental health care workers. Therefore, the transmission probability of these airborne infectious diseases was estimated via mathematical modeling. The transmission probability was modeled for Mycobacterium tuberculosis, Legionella pneumophila, measles virus, influenza virus, and coronaviruses per a modified version of the Wells-Riley equation. This equation incorporated the indoor air quality by using carbon dioxide as a proxy and added the respiratory protection rate from medical face masks and N95 respirators. Scenario-specific analyses, uncertainty analyses, and sensitivity analyses were run to produce probability rates. A high transmission probability was characterized by high patient infectiousness, the absence of respiratory protection, and poor indoor air quality. The highest transmission probabilities were estimated for measles virus (100%), coronaviruses (99.4%), influenza virus (89.4%), and M. tuberculosis (84.0%). The low-risk scenario leads to transmission probabilities of 4.5% for measles virus and 0% for the other pathogens. From the sensitivity analysis, it shows that the transmission probability is strongly driven by indoor air quality, followed by patient infectiousness, and the least by respiratory protection from medical face mask use. Airborne infection transmission of pathogens such as measles virus and coronaviruses is likely to occur in the dental practice. The risk magnitude, however, is highly dependent on specific conditions in each dental clinic. Improved indoor air quality by ventilation, which reduces carbon dioxide, is the most important factor that will either strongly increase or decrease the probability of the transmission of a pathogen.

Endoscopy during the Covid-19 outbreak: experience and recommendations from a single center in a high-incidence scenario

A dramatic SARS-Cov-2 outbreak is hitting Italy hard. To face the new scenario all the hospitals have been re-organised in order to reduce all the outpatient services and to devote almost all their personnel and resources to the management of Covid-19 patients. As a matter of fact, all the services have undergone a deep re-organization guided by: the necessity to reduce exams, to create an environment that helps reduce the virus spread, and to preserve the medical personnel from infection. In these days a re-organization of the endoscopic unit, sited in a high-incidence area, has been adopted, with changes to logistics, work organization and patients selection. With the present manuscript, we want to support gastroenterologists and endoscopists in the organization of a "new" endoscopy unit that responds to the "new" scenario, while remaining fully aware that resources, availability and local circumstances may extremely vary from unit to unit.

Editorial: the airborne microbiome - implications for aerosol transmission and infection control - special issue

Although the title of the Special Issue is 'Airborne Microbiome' the manuscripts received have highlighted a variety of peripheral, yet related aspects of this. The contributions are a mixture of primary research, reviews and commentaries, including: new methods to explore environmental niches where such microbes may grow, their detection and characterisation in the human host, which pathogens are present in the respiratory tract and can be exhaled in human breath to potentially spread via the airborne route, and some strategies for their control. Finally, a historical-to-current overview explores human-microbial interactions, including problems with sampling and detection methods, drug resistance, the role of super-spreaders and issues around research funding.