Modeling of aerosol transmission of airborne pathogens in ICU rooms of COVID-19 patients with acute respiratory failure

Assessing respiratory epidemic potential in French hospitals through collection of close contact data (April-June 2020)

The transmission risk of SARS-CoV-2 within hospitals can exceed that in the general community because of more frequent close proximity interactions (CPIs). However, epidemic risk across wards is still poorly described. We measured CPIs directly using wearable sensors given to all present in a clinical ward over a 36-h period, across 15 wards in three hospitals in April-June 2020. Data were collected from 2114 participants and combined with a simple transmission model describing the arrival of a single index case to the ward to estimate the risk of an outbreak. Estimated epidemic risk ranged four-fold, from 0.12 secondary infections per day in an adult emergency to 0.49 per day in general paediatrics. The risk presented by an index case in a patient varied 20-fold across wards. Using simulation, we assessed the potential impact on outbreak risk of targeting the most connected individuals for prevention. We found that targeting those with the highest cumulative contact hours was most impactful (20% reduction for 5% of the population targeted), and on average resources were better spent targeting patients. This study reveals patterns of interactions between individuals in hospital during a pandemic and opens new routes for research into airborne nosocomial risk.

Effectiveness of SplashGuard Caregiver prototype in reducing the risk of aerosol transmission in intensive care unit rooms of SARS-CoV-2 patients: a prospective and simulation study

BACKGROUND

The contagiousness of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is known to be linked to the emission of bioaerosols. Thus, aerosol-generating procedures (AGPs) could increase the risk of infection among healthcare workers (HCWs).

AIM

To investigate the impact of an aerosol protection box, the SplashGuard Caregiver (SGGC) with suction system, by direct analysis of the presence of viral particles after an AGP, and by using the computational fluid dynamics (CFD) simulation method.

METHODS

This prospective observational study investigated HCWs caring for patients with SARS-CoV-2 admitted to an intensive care unit (ICU). Rooms were categorized as: SGCG present and SGCG absent. Virus detection was performed through direct analysis, and using a CFD model to simulate the movement dynamics of airborne particles produced by a patient's respiratory activities.

FINDINGS

Of the 67 analyses performed, three samples tested positive on quantitative polymerase chain reaction: one of 33 analyses in the SCCG group (3%) and two of 34 analyses in the non-SGCG group (5.9%). CFD simulations showed that: (1) reduction of the gaps of an SGCG could decrease the number of emitted particles remaining airborne within the room by up to 70%; and (2) positioning HCWs facing the opposite direction to the main air flow would reduce their exposure.

CONCLUSIONS

This study documented the presence of SARS-CoV-2 among HCWs in a negative pressure ICU room of an infected patient with or without the use of an SGCG. The simulation will help to improve the design of the SGCG and the positioning of HCWs in the room.

Perspectives on human movement considerations in indoor airflow assessment: a comprehensive data-driven systematic review

Understanding particle dispersion characteristics in indoor environments is crucial for revising infection prevention guidelines through optimized engineering control. The secondary wake flow induced by human movements can disrupt the local airflow field, which enhances particle dispersion within indoor spaces. Over the years, researchers have explored the impact of human movement on indoor air quality (IAQ) and identified noteworthy findings. However, there is a lack of a comprehensive review that systematically synthesizes and summarizes the research in this field. This paper aims to fill that gap by providing an overview of the topic and shedding light on emerging areas. Through a systematic review of relevant articles from the Web of Science database, the study findings reveal an emerging trend and current research gaps on the topic titled Impact of Human Movement in Indoor Airflow (HMIA). As an overview, this paper explores the effect of human movement on human microenvironments and particle resuspension in indoor environments. It delves into the currently available methods for assessing the HMIA and proposes the integration of IoT sensors for potential indoor airflow monitoring. The present study also emphasizes incorporating human movement into ventilation studies to achieve more realistic predictions and yield more practical measures. This review advances knowledge and holds significant implications for scientific and public communities. It identifies future research directions and facilitates the development of effective ventilation strategies to enhance indoor environments and safeguard public health.

Peak risk of SARS-CoV-2 infection within 5 s of face-to-face encounters: an observational/retrospective study

The link between aerosol dynamics and viral exposure risk is not fully understood, particularly during movement and face-to-face interactions. To investigate this, we employed Particle Trace Velocimetry with a laser sheet and a high-speed camera to measure microparticles from a human mannequin's mouth. The average peak time in the non-ventilated condition (expiratory volume, 30 L; passing speed, 5 km/h) was 1.33 s (standard deviation = 0.32 s), while that in the ventilated condition was 1.38 s (standard deviation = 0.35 s). Our results showed that the peak of viral exposure risk was within 5 s during face-to-face encounters under both ventilated and non-ventilated conditions. Moreover, the risk of viral exposure greatly decreased in ventilated conditions compared to non-ventilated conditions. Based on these findings, considering a risk mitigation strategy for the duration of 5 s during face-to-face encounters is expected to significantly reduce the risk of virus exposure in airborne transmission.

The Effectiveness of a Novel Air-Barrier Device for Aerosol Reduction in a Dental Environment: Computational Fluid Dynamics Simulation

The use of equipment such as dental handpieces and ultrasonic tips in the dental environment has potentially heightened the generation and spread of aerosols, which are dispersant particles contaminated by etiological factors. Although numerous types of personal protective equipment have been used to lower contact with contaminants, they generally do not exhibit excellent removal rates and user-friendliness in tandem. To solve this problem, we developed a prototype of an air-barrier device that forms an air curtain as well as performs suction and evaluated the effect of this newly developed device through a simulation study and experiments. The air-barrier device derived the improved design for reducing bioaerosols through the simulation results. The experiments also demonstrated that air-barrier devices are effective in reducing bioaerosols generated at a distance in a dental environment. In conclusion, this study demonstrates that air-barrier devices in dental environments can play an effective role in reducing contaminating particles.

A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches

In the past few years, significant efforts have been made to investigate the transmission of COVID-19. This paper provides a review of the COVID-19 airborne transmission modeling and mitigation strategies. The simulation models here are classified into airborne transmission infectious risk models and numerical approaches for spatiotemporal airborne transmissions. Mathematical descriptions and assumptions on which these models have been based are discussed. Input data used in previous simulation studies to assess the dispersion of COVID-19 are extracted and reported. Moreover, measurements performed to study the COVID-19 airborne transmission within indoor environments are introduced to support validations for anticipated future modeling studies. Transmission mitigation strategies recommended in recent studies have been classified to include modifying occupancy and ventilation operations, using filters and air purifiers, installing ultraviolet (UV) air disinfection systems, and personal protection compliance, such as wearing masks and social distancing. The application of mitigation strategies to various building types, such as educational, office, public, residential, and hospital, is reviewed. Recommendations for future works are also discussed based on the current apparent knowledge gaps covering both modeling and mitigation approaches. Our findings show that different transmission mitigation measures were recommended for various indoor environments; however, there is no conclusive work reporting their combined effects on the level of mitigation that may be achieved. Moreover, further studies should be conducted to understand better the balance between approaches to mitigating the viral transmissions in buildings and building energy consumption.

Assessment of aerosol persistence in ICUs via low-cost sensor network and zonal models

The COVID-19 pandemic raised public awareness about airborne particulate matter (PM) due to the spread of infectious diseases via the respiratory route. The persistence of potentially infectious aerosols in public spaces and the spread of nosocomial infections in medical settings deserve careful investigation; however, a systematic approach characterizing the fate of aerosols in clinical environments has not been reported. This paper presents a methodology for mapping aerosol propagation using a low-cost PM sensor network in ICU and adjacent environments and the subsequent development of the data-driven zonal model. Mimicking aerosol generation by a patient, we generated trace NaCl aerosols and monitored their propagation in the environment. In positive (closed door) and neutral-pressure (open door) ICUs, up to 6% or 19%, respectively, of all PM escaped through the door gaps; however, the outside sensors did not register an aerosol spike in negative-pressure ICUs. The K-means clustering analysis of temporospatial aerosol concentration data suggests that ICU can be represented by three distinct zones: (1) near the aerosol source, (2) room periphery, and (3) outside the room. The data suggests two-phase plume behavior: dispersion of the original aerosol spike throughout the room, followed by an evacuation phase where "well-mixed" aerosol concentration decayed uniformly. Decay rates were calculated for positive, neutral, and negative pressure operations, with negative-pressure rooms clearing out nearly twice as fast. These decay trends closely followed the air exchange rates. This research demonstrates the methodology for aerosol monitoring in medical settings. This study is limited by a relatively small data set and is specific to single-occupancy ICU rooms. Future work needs to evaluate medical settings with high risks of infectious disease transmission.

A numerical approach for preventing the dispersion of infectious disease in a meeting room

Airborne transmission of respiratory aerosols carrying infectious viruses has generated many concerns about cross-contamination risks, particularly in indoor environments. ANSYS Fluent software has been used to investigate the dispersion of the viral particles generated during a coughing event and their transport dynamics inside a safe social-distance meeting room. Computational fluid dynamics based on coupled Eulerian-Lagrangian techniques are used to explore the characteristics of the airflow field in the domain. The main objective of this study is to investigate the effects of the window opening frequency, exhaust layouts, and the location of the air conditioner systems on the dispersion of the particles. The results show that reducing the output capacity by raising the concentration of suspended particles and increasing their traveled distance caused a growth in the individuals' exposure to contaminants. Moreover, decreasing the distance between the ventilation systems installed location and the ceiling can drop the fraction of the suspended particles by over 35%, and the number of individuals who are subjected to becoming infected by viral particles drops from 6 to 2. As well, the results demonstrated when the direction of input airflow and generated particles were the same, the fraction of suspended particles of 4.125%, whereas if the inputs were shifted to the opposite direction of particle injection, the fraction of particles in fluid increased by 5.000%.

Effects of surgical masks on aerosol dispersion in professional singing

BACKGROUND

In the CoVID-19 pandemic, singing came into focus as a high-risk activity for the infection with airborne viruses and was therefore forbidden by many governmental administrations.

OBJECTIVE

The aim of this study is to investigate the effectiveness of surgical masks regarding the spatial and temporal dispersion of aerosol and droplets during professional singing.

METHODS

Ten professional singers performed a passage of the Ludwig van Beethoven's "Ode of Joy" in two experimental setups-each with and without surgical masks. First, they sang with previously inhaled vapor of e-cigarettes. The emitted cloud was recorded by three cameras to measure its dispersion dynamics. Secondly, the naturally expelled larger droplets were illuminated by a laser light sheet and recorded by a high-speed camera.

RESULTS

The exhaled vapor aerosols were decelerated and deflected by the mask and stayed in the singer's near-field around and above their heads. In contrast, without mask, the aerosols spread widely reaching distances up to 1.3 m. The larger droplets were reduced by up to 86% with a surgical mask worn.

SIGNIFICANCE

The study shows that surgical masks display an effective tool to reduce the range of aerosol dispersion during singing. In combination with an appropriate aeration strategy for aerosol removal, choir singers could be positioned in a more compact assembly without contaminating neighboring singers all singers.

Pathways to community transmission of COVID-19 due to rapid evaporation of respiratory virulets

HYPOTHESIS

The formation of virus-laden colloidal respiratory microdroplets - the sneeze or cough virulets and their evaporation driven miniaturization in the open air are found to have a significant impact on the community transmission of COVID-19 pandemic.

SIMULATION DETAILS

We simulate the motions and trajectories of virulets by employing laminar fluid flow coupled with droplet tracing physics. A force field analysis has been included considering the gravity, drag, and inertial forces to unleash some of the finer features of virulet trajectories leading to the droplet and airborne transmissions of the virus. Furthermore, an analytical model corroborates temperature (T) and relative humidity (RH) controlled droplet miniaturization.

RESULTS

The study elucidates that the tiny (1-50 µm) and intermediate (60-100 µm) size ranged virulets tend to form bioaerosol and facilitate an airborne transmission while the virulets of larger dimensions (300 to 500 µm) are more prone to gravity dominated droplet transmission. Subsequently, the mapping between the T and RH guided miniaturization of virulets with the COVID-19 cases for six different cities across the globe justifies the significant contribution of miniaturization-based bioaerosol formation for community transmission of the pandemic.

Multi-objective performance assessment of HVAC systems and physical barriers on COVID-19 infection transmission in a high-speed train

A computational fluid dynamics (CFD) simulation was performed to model and study the transmission risk associated with cough-related SARS-CoV-2 droplets in a real-world high-speed train (HST). In this study, the evaporating of the droplets was considered. Simulation data were post-processed to assess the fraction of the particles deposited on each passenger's face and body, suspended in air, and escaped from exhausts. Firstly, the effects of temperature, relative humidity, ventilation rate, injection source, exhausts' location and capacity, and adding the physical barriers on evaporation and transport of respiratory droplets are investigated in long distance HST. The results demonstrate that overall, 6–43% of the particles were suspended in the cabin after 2.7 min, depending on conditions, and 3–58% of the particles were removed from the cabin in the same duration. Use of physical barriers and high ventilation rate is therefore recommended for both personal and social protection. We found more exhaust capacity and medium relative humidity to be effective in reducing the particles' transmission potential across all studied scenarios. The results indicate that reducing ventilation rate and exhaust capacity, increased aerosols shelf time and dispersion throughout the cabin.

Effect of inlet-outlet configurations on the cross-transmission of airborne bacteria between animal production buildings

Cross-transmission of airborne pathogens between buildings facilitates the spread of both human and animal diseases. Rational spatial arrangement of buildings and air inlet-outlet design are well-established preventive measures, but the effectiveness of current configurations for mitigating pathogens cross-transmission is still under assessment. An intensive field study in a laying hen farm was conducted to elucidate the spatial distribution of airborne bacteria (AB) and the source of AB at the inlets under different wind regimes. We found higher concentrations of AB at the interspace and sidewall inlets of buildings with sidewall exhaust systems than at those with endwall exhaust systems. We observed significant differences in bacterial diversity and richness at the interspace and sidewall inlets between buildings with side exhaust systems and those with endwall exhaust systems. We further found that the AB emitted from buildings could translocate to the sidewall inlets of adjacent building to a greater extent between buildings with sidewall exhaust systems than between those with endwall exhaust systems. Our findings revealed that sidewall exhaust systems aggravate cross-transmission of AB between buildings, suggesting that endwall exhaust systems or other compensatory preventive measures combined with sidewall exhaust systems could be a better choice to suppress airborne cross-transmission.

Exposure Risk to Medical Staff in a Nasopharyngeal Swab Sampling Cabin under Four Different Ventilation Strategies

Medical staff working in a nasopharyngeal swab sampling cabin are exposed to a higher exposure risk of COVID-19. In this study, computational fluid dynamics (CFD) are used to evaluate the exposure risk to medical staff in a nasopharyngeal swab sampling cabin of Chinese customs under four different ventilation strategies, i.e., multiple supply fans ventilation (MSFV), multiple exhaust fans ventilation (MEFV), single exhaust fan and outer windows closed ventilation (SEFV), and single exhaust fan and outer windows opened ventilation (SEFV-W). The impact of physical partitions on exposure risk is also discussed. The results show that MSFV performed best in reducing exposure risk. No significant difference was found between MEFV and SEFV. SEFV-W performed better than SEFV with a ventilation rate of 10–50 L/(s∙Person), while it performed worse with a ventilation rate of 50–90 L/(s∙Person). The exposure risk to medical staff did not decrease linearly with the increase in the ventilation flow rate under the four ventilation strategies. For MSFV, the installation of partitions is conducive to the reduction in the exposure risk. This study is expected to provide some guidance for ventilation designs in sampling cabins.

3D modelling and simulation of the dispersion of droplets and drops carrying the SARS-CoV-2 virus in a railway transport coach

Computational fluid dynamics (CFD) modelling and 3D simulations of the air flow and dispersion of droplets or drops in semi-confined ventilated spaces have found topical applications with the unfortunate development of the Covid-19 pandemic. As an illustration of this scenario, we have considered the specific situation of a railroad coach containing a seated passenger infected with the SARS-CoV-2 virus (and not wearing a face mask) who, by breathing and coughing, releases droplets and drops that contain the virus and that present aerodynamic diameters between 1 and 1000 µm. The air flow is generated by the ventilation in the rail coach. While essentially 3D, the flow is directed from the bottom to the top of the carriage and comprises large to small eddies visualised by means of streamlines. The space and time distribution of the droplets and drops is computed using both an Eulerian model and a Lagrangian model. The results of the two modelling approaches are fully consistent and clearly illustrate the different behaviours of the drops, which fall down close to the infected passenger, and the droplets, which are carried along with the air flow and invade a large portion of the rail coach. This outcome is physically sound and demonstrates the relevance of CFD for simulating the transport and dispersion of droplets and drops with any diameter in enclosed ventilated spaces. As coughing produces drops and breathing produces droplets, both modes of transmission of the SARS-CoV-2 virus in human secretions have been accounted for in our 3D numerical study. Beyond the specific, practical application of the rail coach, this study offers a much broader scope by demonstrating the feasibility and usefulness of 3D numerical simulations based on CFD. As a matter of fact, the same computational approach that has been implemented in our study can be applied to a huge variety of ventilated indoor environments such as restaurants, performance halls, classrooms and open-plan offices in order to evaluate if their occupation could be critical with respect to the transmission of the SARS-CoV-2 virus or to other airborne respiratory infectious agents, thereby enabling relevant recommendations to be made.

Defining biological and biophysical properties of SARS-CoV-2 genetic material in wastewater

SARS-CoV-2 genetic material has been detected in raw wastewater around the world throughout the COVID-19 pandemic and has served as a useful tool for monitoring community levels of SARS-CoV-2 infections. SARS-CoV-2 genetic material is highly detectable in a patient's feces and the household wastewater for several days before and after a positive COVID-19 qPCR test from throat or sputum samples. Here, we characterize genetic material collected from raw wastewater samples and determine recovery efficiency during a concentration process. We find that pasteurization of raw wastewater samples did not reduce SARS-CoV-2 signal if RNA is extracted immediately after pasteurization. On the contrary, we find that signal decreased by approximately half when RNA was extracted 24-36 h post-pasteurization and ~90% when freeze-thawed prior to concentration. As a matrix control, we use an engineered enveloped RNA virus. Surprisingly, after concentration, the recovery of SARS-CoV-2 signal is consistently higher than the recovery of the control virus leading us to question the nature of the SARS-CoV-2 genetic material detected in wastewater. We see no significant difference in signal after different 24-hour temperature changes; however, treatment with detergent decreases signal ~100-fold. Furthermore, the density of the samples is comparable to enveloped retrovirus particles, yet, interestingly, when raw wastewater samples were used to inoculate cells, no cytopathic effects were seen indicating that wastewater samples do not contain infectious SARS-CoV-2. Together, this suggests that wastewater contains fully intact enveloped particles.

Rôle de la transmission air lors d’un Cluster de cas Covid-19 en Pneumologie : investigation épidémiologique, analyse génomique et modélisation d’aérosols

Introduction

La pandémie COVID-19 a suscité de nombreuses inquiétudes quant aux risques de contamination croisée en milieu hospitalier. Les aérosols chargés de virus produits par les patients infectés peuvent se propager dans les pièces mal ventilées et mettre en danger les soignants et les patients non infectés [1].

Objectif

Caractérisation du mode de transmission air de SARS Cov-2, lors de deux clusters Covid-19 en janvier et avril 2021 dans un service de Pneumologie.

Méthodes

Quatre étapes d’investigations: (1) Enquête épidémiologique avec chronogramme du cluster; (2) Enquête environnementale: prélèvements d’air à la recherche de SARS Cov-2 et mesure de teneur en CO₂; (3) Comparaison génotypique des souches de SARS Cov-2 des patients et des soignants; (4) Modélisation d’aérosols en 3 dimensions dans les chambres et couloirs du service. Différents scénarios à l’aide de cinq “patients” virtuels infectés par des particules de 3 microns, répartis dans le service. Le lâcher d’aérosols permet de voir où celle-ci se déplacent, en fonction d’ouverture ou de fermeture des portes et/ou fenêtres et de l’arrêt ou non de l’extraction d’air.

Résultats

Au total, 31 cas nosocomiaux chez 14 soignants (23%) et 17 patients (39%). Un même profil génomique entre les souches patients. 9 parmi 35 contrôles d’air sont RT-PCR positifs (26%). Les cultures virales sont négatives. L’extraction d’air dans les chambres est très faible (6% en 70 secondes), vu le faible taux de renouvellement d’air = 2,8 volumes/heure. La modélisation montre une ascension verticale d’aérosols vers le plafond suivi d’une dispersion le long des poutres froides des chambres puis stagnation du côté opposé au patient. Les aérosols diffusent dans les couloirs si les portes sont ouvertes. L’ouverture d’une fenêtre crée un appel d’air des autres chambres en moins de 76 secondes.

Conclusion

Un taux de renouvellement d’air insuffisant avec un déficit d’extraction semble avoir contribué à la transmission air d’aérosols infectés aux soignants. L’absence de port de lunettes par les soignants et le non port de masque par les patients, ont eu un rôle d’accélérateur de la diffusion de la souche épidémique.

Modeling and Simulations of Moving Droplets in Relation to SARS-CoV-19 Generated by Respiratory System

Contemporary issues such as epidemics and the prevalence of infectious indicate that there is a pressing need to better understand the dynamics of transmission in air and facemasks. Consistent with previous literature, coronavirus disease (COVID-2019) is caused by the novel virus SARS-CoV-2. Coronavirus adds a new element to fluid fragmentation leading to respiratory droplets and which are transmitted via air during coughing, sneezing and talking. The behavior of virus-laden droplets of saliva particles arising from a human cough is described by Navier–Stokes equation for turbulent flow. The predicted velocity and pressure for droplets flow with time are presented. Hence, wall-normal profiles of velocity, pressure and concentration are obtained from boundary-layer approximations and the Navier–Stokes equations are solved on a two-dimensional shell mesh. The purpose of this study is to provide a perspective on the role of masks in the COVID-19 pandemic with an emphasis on the mechanism of droplet leakage and the droplet dispersion in this masks medical non-pharmaceutical intervention.

Surfaces and Air contamination by SARS-CoV-2 using High-flow Nasal Oxygenation or Assisted Mechanical Ventilation System in ICU rooms of COVID-19 Patients

BACKGROUND

Understanding patterns of environmental contamination by SARS-CoV-2 is essential for infection prevention policies.

METHODS

We screened surfaces and air samples from single bed ICU rooms of COVID-19 adult patients for SARS-CoV-2 RNA and viable viruses.

RESULTS AND DISCUSSION

We evidenced viral RNA environmental contamination in 76% of 100 surfaces samples and in 30% of 40 air samples without any viable virus detection by cell culture assays. No significant differences of viral RNA levels on surfaces and in ambient air were observed between rooms of patients with assisted mechanical ventilation and those of patients with high-flow nasal cannula system. Using an original experimental SARS-CoV-2 infection model of surfaces, we assessed that infectious viruses might have been present on benches within 15 hours before the time of sampling in patient rooms.

CONCLUSIONS

We observed that SARS-CoV-2 environmental contamination around COVID-19 patients hospitalized in single ICU rooms was extensive and that a high-flow nasal cannula system did not generate more viral aerosolization than a mechanical ventilation system in COVID-19 patients. Despite an absence of SARS-CoV-2 viable particles in study samples, our experimental model confirmed the need to apply strict environmental disinfection procedures and classical standard and droplet precautions in ICU wards.

Computational fluid dynamics-based disease transmission modeling of SARS-CoV-2 intensive care unit

Covid-19 has become one of the most severe diseases causing acute respiratory problems and has killed millions of people worldwide. It was declared as the ongoing pandemic by the World Health Organization. It is an infectious virus which can be transmitted by sneezing, coughing and exhalation of air by any infected person. There are certain places having high chances of becoming contaminated like hospital rooms. In this context, we studied the transmission of Covid-19 particles in an ICU room. We have considered the combined effect of both of air-conditioning (AC) and ceiling fan in the room. The infected person can transmit the disease when under influence of fan and AC. The work highlights the flow of aerosol particles considering the combined effect as well as the individual effects of fan and AC. The results also emphasized that the aerosol particle flow have a promising application in sanitizing the room.

A position statement and practical guide to the use of particulate filtering facepiece respirators (N95, FFP2, or equivalent) for South African health workers exposed to respiratory pathogens including Mycobacterium tuberculosis and SARS-CoV-2

SUMMARY

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is transmitted mainly by aerosol in particles <10 µm that can remain suspended for hours before being inhaled. Because particulate filtering facepiece respirators ('respirators'; e.g. N95 masks) are more effective than surgical masks against bio-aerosols, many international organisations now recommend that health workers (HWs) wear a respirator when caring for individuals who may have COVID-19. In South Africa (SA), however, surgical masks are still recommended for the routine care of individuals with possible or confirmed COVID-19, with respirators reserved for so-called aerosol-generating procedures. In contrast, SA guidelines do recommend respirators for routine care of individuals with possible or confirmed tuberculosis (TB), which is also transmitted via aerosol. In health facilities in SA, distinguishing between TB and COVID-19 is challenging without examination and investigation, both of which may expose HWs to potentially infectious individuals. Symptom-based triage has limited utility in defining risk. Indeed, significant proportions of individuals with COVID-19 and/or pulmonary TB may not have symptoms and/or test negative. The prevalence of undiagnosed respiratory disease is therefore likely significant in many general clinical areas (e.g. waiting areas). Moreover, a proportion of HWs are HIV-positive and are at increased risk of severe COVID-19 and death.

RECOMMENDATIONS

Sustained improvements in infection prevention and control (IPC) require reorganisation of systems to prioritise HW and patient safety. While this will take time, it is unacceptable to leave HWs exposed until such changes are made. We propose that the SA health system adopts a target of 'zero harm', aiming to eliminate transmission of respiratory pathogens to all individuals in every healthcare setting. Accordingly, we recommend: the use of respirators by all staff (clinical and non-clinical) during activities that involve contact or sharing air in indoor spaces with individuals who: (i) have not yet been clinically evaluated; or (ii) are thought or known to have TB and/or COVID-19 or other potentially harmful respiratory infections;the use of respirators that meet national and international manufacturing standards;evaluation of all respirators, at the least, by qualitative fit testing; andthe use of respirators as part of a 'package of care' in line with international IPC recommendations. We recognise that this will be challenging, not least due to global and national shortages of personal protective equipment (PPE). SA national policy around respiratory protective equipment enables a robust framework for manufacture and quality control and has been supported by local manufacturers and the Department of Trade, Industry and Competition. Respirator manufacturers should explore adaptations to improve comfort and reduce barriers to communication. Structural changes are needed urgently to improve the safety of health facilities: persistent advocacy and research around potential systems change remain essential.