Respiratory Particles Research Articles

Evaluation of transmission risk of respiratory particles under different ventilation strategies in an elevator

Evaluation of transmission risk of respiratory particles under different ventilation strategies in an elevator

Respiratory particles: from analytical estimates to disease transmission

Respiratory particles containing infectious pathogens are responsible for a large number of diseases. To define health politics and save lives, it is important to study their transmission mechanisms, namely the path of particles once expelled. This path depends on several driving factors as intrinsic properties of particles, environmental aspects and morphology of the scenario. Following physical arguments and taking into account the results of experimental works, we consider a mathematical drift model for the mixture composed by two phases: air and particles. The relative motion between the two phases is described by a kinematic constitutive relation. We prove the stability of the model for fixed times and establish an a priori estimate for the total number of infectious particles. The upper bound of this estimate exhibits sound physical dependencies on the driving factors, in agreement with the experimental literature and mounting epidemiological evidences. Namely, we establish that the amount of particles expelled and their emission rate can explain why some people are superspreaders. Several numerical simulations illustrate the theoretical results.

Study on the Effects of Dust Particle Size and Respiratory Intensity on the Pattern of Respiratory Particle Deposition in Humans

Nowadays, dust exposure pollution is receiving a lot of attention due to its significant impact on public health. To investigate the impact of dust particle size and human respiratory strength on respiratory particle deposition patterns, data was collected through on‐site surveys. The study analyzed the equivalent respiratory strength, dust environment characteristics, and bronchial particle escape and deposition patterns of humans in fully mechanized mining faces at various operating times. This was done using ergonomic energy consumption simulation experiments and a fluid–solid interaction method of CFD‐DEM. The findings revealed that as humans worked continuously for 5, 15, 30, 45, and 60 min, their respiratory intensity corresponded to 8, 18, 30, 42, and 50 L/min, respectively. According to the field investigation and particle size analysis, the particle size distribution of 1~5, 5~10, 10~20, 20~30, and 30~40 μm particles accounted for 36%, 26%, 15%, 11%, and 10%, respectively. In general, the deposition rate of dust was highest in the main bronchus of the respiratory tract, followed by the trachea area. Particles ranging from 5 to 10 μm in size were observed to have a higher likelihood of escaping from the tertiary bronchioles and entering the secondary bronchial regions. Conversely, particles larger than 20 μm exhibited a deposition rate of up to 80% in the tertiary bronchial regions. It was noted that the bronchial deposition rate of particles of varying sizes increased with respiratory strength, with smaller particles showing greater sensitivity to changes in respiratory strength in terms of the deposition fraction. Among the different particle sizes, the deposition rate of 5–10 μm particles exhibited the most variation with increasing respiration intensity, ranging up to 17%.

Investigation of the Emission Rate of Particles when Musicians Play Wind, Woodwind, and Brass Instruments

In the context of the high risk of airborne transmission of COVID-19, the question of the production of particles while playing wind instruments is highly relevant. Therefore, in this study, 23 professional musicians played their instruments in a cleanroom in cleanroom-grade clothing. The most common orchestral wind instruments flute, oboe, clarinet, and trumpet were therefore chosen. Aerosol measurements using a laser particle counter were conducted to quantify the emission rate of respiratory particles. Orchestral excerpts as well as sustained tones in two dynamic levels were played. The emitted particles were mostly in a submicron size range. For all instruments besides the clarinet, an influence of the loudness of playing on the emission rate could be observed. The emission rates for all musical instruments were independent of the passages played. Flute and oboe showed similar emission rates but lower than the values for clarinet and trumpet. While playing a note with a small volume, the flute, oboe, and trumpet have a similar emission rate as found for speaking.

Dynamics and Viability of Airborne Respiratory Syncytial Virus under Various Indoor Air Conditions.

The factors governing the viability of airborne viruses embedded within respiratory particles are not well understood. This study aimed to investigate the relative humidity (RH)-dependent viability of airborne respiratory syncytial virus (RSV) in simulated respiratory particles suspended in various indoor air conditions. We tested airborne RSV viability in three static indoor air conditions, including sub-hysteresis (RH < 39%), hysteresis (39% < RH < 65%), and super-hysteresis (RH > 65%) air as well as in three dynamic indoor air conditions, including the transitions between the static conditions. The dynamic conditions were hysteresis → super-hysteresis → hysteresis, sub-hysteresis → hysteresis, and super-hysteresis → hysteresis. We found that after 45 min of particle aging in static conditions, the viability of RSV in sub-hysteresis, hysteresis, and super-hysteresis air was 0.72% ± 0.06%, 0.03% ± 0.006%, and 0.27% ± 0.008%, respectively. After 45 min of aging in dynamic conditions, the RSV viability decreased for particles that remained in a liquid (deliquesced) state during aging when compared with particles in a solid (effloresced) state. The decreased viability of airborne RSV for deliquesced particles is consistent with prolonged exposure to elevated aqueous solutes. These results represent the first measurements of the survival of airborne RSV over particle aging time, with equal viability in low, intermediate, and high RHs at 5 and 15 min and a V-shaped curve after 45 min.

Respiratory particle emission rates from children during speaking

The number of respiratory particles emitted during different respiratory activities is one of the main parameters affecting the airborne transmission of respiratory pathogens. Information on respiratory particle emission rates is mostly available for adults (few studies have investigated adolescents and children) and generally involves a limited number of subjects. In the present paper we attempted to reduce this knowledge gap by conducting an extensive experimental campaign to measure the emission of respiratory particles of more than 400 children aged 6 to 12 years while they pronounced a phonetically balanced word list at two different voice intensity levels (“speaking” and “loudly speaking”). Respiratory particle concentrations, particle distributions, and exhaled air flow rates were measured to estimate the respiratory particle emission rate. Sound pressure levels were also simultaneously measured. We found out that median respiratory particle emission rates for speaking and loudly speaking were 26 particles s−1 (range 7.1–93 particles s−1) and 41 particles s−1 (range 10–146 particles s−1), respectively. Children sex was significant for emission rates, with higher emission rates for males during both speaking and loudly speaking. No effect of age on the emission rates was identified. Concerning particle size distributions, for both respiratory activities, a main mode at approximately 0.6 µm and a second minor mode at < 2 µm were observed, and no differences were found between males and females. This information provides important input parameters in predictive models adopted to estimate the transmission risk of airborne pathogens in indoor spaces.

An experimental study on lung deposition of inhaled 2 μm particles in relation to lung characteristics and deposition models

BackgroundThe understanding of inhaled particle respiratory tract deposition is a key link to understand the health effects of particles or the efficiency for medical drug delivery via the lung. However, there are few experimental data on particle respiratory tract deposition, and the existing data deviates considerably when comparing results for particles > 1 μm.MethodsWe designed an experimental set-up to measure deposition in the respiratory tract for particles > 1 μm, more specifically 2.3 μm, with careful consideration to minimise foreseen errors. We measured the deposition in seventeen healthy adults (21–68 years). The measurements were performed at tidal breathing, during three consecutive 5-minute periods while logging breathing patterns. Pulmonary function tests were performed, including the new airspace dimension assessment (AiDA) method measuring distal lung airspace radius (rAiDA). The lung characteristics and breathing variables were used in statistical models to investigate to what extent they can explain individual variations in measured deposited particle fraction. The measured particle deposition was compared to values predicted with whole lung models. Model calculations were made for each subject using measured variables as input (e.g., breathing pattern and functional residual capacity).ResultsThe measured fractional deposition for 2.3 μm particles was 0.60 ± 0.14, which is significantly higher than predicted by any of the models tested, ranging from 0.37 ± 0.08 to 0.53 ± 0.09. The multiple-path particle dosimetry (MPPD) model most closely predicted the measured deposition when using the new PNNL lung model. The individual variability in measured particle deposition was best explained by breathing pattern and distal airspace radius (rAiDA) at half inflation from AiDA. All models underestimated inter-subject variability even though the individual breathing pattern and functional residual capacity for each participant was used in the model.ConclusionsWhole lung models need to be tuned and improved to predict the respiratory tract particle deposition of micron-sized particles, and to capture individual variations – a variation that is known to be higher for aged and diseased lungs. Further, the results support the hypothesis that the AiDA method measures dimensions in the peripheral lung and that rAiDA, as measured by the AiDA, can be used to better understand the individual variation in the dose to healthy and diseased lungs.

Respiratory function of workers at some wood factories in Bac Tu Liem district, 2022

Objectives: This study aimed to assess the respiratory function status and associated factors among workers in wood factories in Bac Tu Liem district. Methods: A total of 80 workers from six woodworking establishments participated in this cross-sectional study. Respiratory symptom questionnaires based on ECCS-87 and ATS-DLD-78a were used to collect data on symptoms experienced within the past 12 months. Respiratory function measurements were also conducted during breaks and at the end of shifts. Results: Workers with 3-5 years of experience accounted for 63.8% of the total sample. The majority (92.5%) were exposed to harmful workplace factors for more than 8 hours per day. Only 13.8% reported using full personal protective equipment. Concentrations of respiratory particles and Total Suspended Particulate (TSP) in wood facilities exceeded allowable standards. Cough was the most commonly reported respiratory symptom, with a prevalence of 28.8%. Approximately 66.3% of subjects had normal respiratory function, while restrictive ventilation disorder accounted for the highest proportion of respiratory disorders at 21.3%. Statistical analysis revealed significant associations between respiratory dysfunction and work experience (OR=2.56, p&lt;0.01), duration of exposure to hazardous factors (OR=1.8, p&lt;0.05), use of personal protective equipment (OR=7.12, p&lt;0.05), and the occurrence of respiratory symptoms (OR=1.73, p&lt;0.01). Conclusions: workers in furniture manufacturing facilities in Bac Tu Liem district face exposure to high concentrations of total particles, respiratory particles, and toxic gases that surpass permissible standards. The study also found a significant relationship between respiratory dysfunction and employee characteristics. Keywords: Respiratory function, wood workers, wood factories.

Inactivation mechanisms of influenza A virus under pH conditions encountered in aerosol particles as revealed by whole-virus HDX-MS.

Multiple respiratory viruses, including influenza A virus (IAV), can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. Indoors, small exhaled aerosols undergo rapid acidification to pH ~4. IAV is known to be sensitive to mildly acidic conditions encountered within host endosomes; however, it is unknown whether the same mechanisms could mediate viral inactivation within the more acidic aerosol micro-environment. Here, we identified that transient exposure to pH 4 caused IAV inactivation by a two-stage process, with an initial sharp decline in infectious titers mainly attributed to premature attainment of the post-fusion conformation of viral protein haemagglutinin (HA). Protein changes were observed by hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) as early as 10 s post-exposure to acidic conditions. Our HDX-MS data are in agreement with other more labor-intensive structural analysis techniques, such as X-ray crystallography, highlighting the ease and usefulness of whole-virus HDX-MS for multiplexed protein analyses, even within enveloped viruses such as IAV. Additionally, virion integrity was partially but irreversibly affected by acidic conditions, with a progressive unfolding of the internal matrix protein 1 (M1) that aligned with a more gradual decline in viral infectivity with time. In contrast, no acid-mediated changes to the genome or lipid envelope were detected. Improved understanding of respiratory virus fate within exhaled aerosols constitutes a global public health priority, and information gained here could aid the development of novel strategies to control the airborne persistence of seasonal and/or pandemic influenza in the future. IMPORTANCE It is well established that COVID-19, influenza, and many other respiratory diseases can be transmitted by the inhalation of aerosolized viruses. Many studies have shown that the survival time of these airborne viruses is limited, but it remains an open question as to what drives their infectivity loss. Here, we address this question for influenza A virus by investigating structural protein changes incurred by the virus under conditions relevant to respiratory aerosol particles. From prior work, we know that expelled aerosols can become highly acidic due to equilibration with indoor room air, and our results indicate that two viral proteins are affected by these acidic conditions at multiple sites, leading to virus inactivation. Our findings suggest that the development of air treatments to quicken the speed of aerosol acidification would be a major strategy to control infectious bioburdens in the air.

Evaluation of intervention measures in reducing the driver's exposure to respiratory particles in a taxi with infected passengers

In the fifth wave of the COVID-19 epidemic in Hong Kong in early 2022, the large number of infected persons caused a shortage of ambulances and transportation vehicles operated by the government. To solve the problem, taxi drivers were recruited to transport infected persons to hospitals in their taxis. However, many of the drivers were infected after they began to participate in the plan. To tackle this issue, the present study numerically evaluated the effectiveness of several intervention measures in reducing the infection risk for taxi drivers. First, experiments were conducted inside a car to validate the large-eddy simulation (LES)-Lagrangian model for simulation of particle transport in a car. The validated model was then applied to calculate the particle dispersion and deposition in a Hong Kong taxi with intervention measures that included opening windows, installing partitions, and using a far-UVC lamp. The results show that opening the windows can significantly reduce the driver's total exposure by 97.4 %. Installing partitions and using a far-UVC lamp can further reduce the infection risk of driver by 55.9 % and 32.1 %, respectively. The results of this study can be used to support the implementation of effective intervention measures to protect taxi drivers from infection.

Binding of respiratory syncytial virus particles to platelets does not result in their degranulation in vitro.

Respiratory syncytial virus (RSV) is a major cause of severe respiratory infection in infants and the elderly. The mechanisms behind severe RSV disease are incompletely understood, but a dysregulated immune response probably plays an important role. Platelets are increasingly being recognized as immune cells and are involved in the pathology of several viruses. The release of chemokines from platelets upon activation may attract, for example, neutrophils to the site of infection, which is a hallmark of RSV pathology. In addition, since RSV infections are sometimes associated with cardiovascular events and platelets express several known RSV receptors, we investigated the effect of RSV exposure on platelet degranulation. Washed human platelets were incubated with sucrose-purified RSV particles. P-selectin and CD63 surface expression and CCL5 secretion were measured to assess platelet degranulation. We found that platelets bind and internalize RSV particles, but this does not result in degranulation. Our results suggest that platelets do not play a direct role in RSV pathology by releasing chemokines to attract inflammatory cells.

ASSESSMENT OF USED NOSE MASKS FOR THE PRESENCE OF SARS-CoV-2

The science around the use of masks by the public to impede COVID-19 transmission is advancing rapidly. A primary route of transmission of COVID-19 is via respiratory particles, and it is known to be transmissible from pre-symptomatic, pauci-symptomatic and asymptomatic individuals. This study was carried with the aim of evaluating the presence of SARS-CoV-2 in used nose masks in Benin City. Three different locations were chosen; University of Benin Teaching Hospital, Department of Microbiology, Faculty of Life Sciences and Ekae market at Sapele Road. New packs of sealed nose masks were purchased and used in the course of the study. The study was conducted within the dry and wet seasons. Nose masks were distributed to different volunteers in the various study locations at day 1, day 2 and day 3. The nose masks were retrieved at the time lapse from the volunteers and taken to the laboratory for analysis. Samples of nose masks retrieved from the volunteers were subjected to SARS-CoV-2 identification test was carried out on the nosemask samples. Also used and unused nose masks were subjected to viral detection technique to determine the possible presence of SARS-COV 2. Viral detection techniques revealed no presence of SARS-CoV-2 in nose masks samples analysed. This study provided early evidence for the microbial contamination of nose masks which should be a basis for improved hygienic practices by nose mask wearers.

Inhalation exposure assessment techniques on ventilation dilution of infectious respiratory particles in a retrofitted hospital lung function room

Controlling the spread of respiratory infections in healthcare settings is important to prevent nosocomial infections. To assess the effectiveness of commonly used techniques in the hospital for evaluating the performance of building retrofit to reduce the risk of nosocomial infection, we employed computational fluid dynamics (CFD) simulation, real-time carbon dioxide (CO2) monitoring, microorganism culturing, and microorganism sequencing. These techniques can quantitatively assess the direct and indirect inhalation exposure risk of healthcare workers (HCWs) to infectious respiratory particles (IRPs) exhaled by patients in a hospital lung function room under two ventilation configurations. Originally, the ventilation system provided 2 air changes per hour (ACH) for clean air and 2 ACH for recirculated air. After retrofitting, the ventilation system was modified to increase clean air to 6 ACH and remove recirculated air. However, the assessment techniques yielded conflicting results regarding the percentage differences in exposure risk before and after the retrofit. The findings indicated that the retrofit system reduced indirect inhalation exposure risk, as estimated by real-time CO2 monitoring and microorganism culture, by over 50.00%. However, the CFD simulation indicated an increase in inhalation exposure risk when 6 ACH of clean air was supplied. These results suggest that removing recirculated air and increasing the air change rate are effective in reducing long-range indirect inhalation exposure in the lung function room. However, they are insufficient to minimize the direct inhalation exposure of patients exhaling IRPs in close proximity. Given the conflicting results obtained from the commonly accepted techniques used in our study, it is necessary to provide a better understanding of infection control associated with the ventilation dilution of IRPs for hospital architects, hospital healthcare workers, and built-environment researchers.

Correction to “Size-Resolved Elemental Composition of Respiratory Particles in Three Healthy Subjects”

ADVERTISEMENT RETURN TO ARTICLES ASAPPREVCorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Size-Resolved Elemental Composition of Respiratory Particles in Three Healthy Subjects”Aaron J. Prussin IIAaron J. Prussin, IIMore by Aaron J. Prussin, IIhttps://orcid.org/0000-0002-9991-8537, Zezhen ChengZezhen ChengMore by Zezhen Chenghttps://orcid.org/0000-0001-6320-4519, Weinan LengWeinan LengMore by Weinan Leng, Swarup ChinaSwarup ChinaMore by Swarup Chinahttps://orcid.org/0000-0001-7670-335X, and Linsey C. Marr*Linsey C. MarrMore by Linsey C. Marrhttps://orcid.org/0000-0003-3628-6891Cite this: Environ. Sci. Technol. Lett. 2023, XXXX, XXX, XXX-XXXPublication Date (Web):June 13, 2023Publication History Received5 June 2023Accepted9 June 2023Revised9 June 2023Published online13 June 2023https://doi.org/10.1021/acs.estlett.3c00380© 2023 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views-Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (824 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Color Get e-Alerts

Lung aerosol particle emission increases with age at rest and during exercise

Airborne respiratory aerosol particle transmission of pathogens such as severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), influenza, or rhinoviruses plays a major role in the spread of infectious diseases. The infection risk is increased during indoor exercise, as aerosol particle emission can increase by more than 100-fold from rest to maximal exercise. Earlier studies have investigated the effect of factors such as age, sex, and body mass index (BMI), but only at rest and without taking ventilation into account. Here, we report that during both rest and exercise, subjects aged 60 to 76y emit on average more than twice as many aerosol particles per minute than subjects aged 20 to 39y. In terms of volume, older subjects emit on average five times as much dry volume (i.e., the residue of dried aerosol particles) than younger subjects. There was no statistically significant effect of sex or BMI within the test group. Together, this suggests that aging of the lung and respiratory tract is associated with an increased generation of aerosol particles irrespective of ventilation. Our findings demonstrate that age and exercise increase aerosol particle emission. In contrast, sex or BMI only have minor effects.

Mitigation of Respirable Aerosol Particles from Speech and Language Therapy Exercises

Phonation and speech are known sources of respirable aerosol in humans. Voice assessment and treatment manipulate all the subsystems of voice production, and previous work (Saccente-Kennedy et al., 2022) has demonstrated such activities can generate >10 times more aerosol than conversational speech and 30 times more aerosol than breathing. Aspects of voice therapy may therefore be considered aerosol generating procedures and pose a greater risk of potential airborne pathogen (eg, SARS-CoV-2) transmission than typical speech. Effective mitigation measures may be required to ensure safe service delivery for therapist and patient. To assess the effectiveness of mitigation measures in reducing detectable respirable aerosol produced by voice assessment/therapy. We recruited 15 healthy participants (8 cis-males, 7 cis-females), 9 of whom were voice-specialist speech-language pathologists. Optical Particle Sizers (OPS) (Model 3330, TSI) were used to measure the number concentration of respirable aerosol particles (0.3 µm-10 µm) generated during a selection of voice assessment/therapy tasks, both with and without mitigation measures in place. Measurements were performed in a laminar flow operating theatre, with near-zero background aerosol concentration, allowing us to quantify the number concentration of respiratory aerosol particles produced. Mitigation measures included the wearing of Type IIR fluid resistant surgical masks, wrapping the same masks around the end of straws, and the use of heat and moisture exchange microbiological filters (HMEFs) for a water resistance therapy (WRT) task. All unmitigated therapy tasks produced more aerosol than unmasked breathing or speaking. Mitigation strategies reduced detectable aerosol from all tasks to a level significantly below, or no different to, that of unmasked breathing. Pooled filtration efficiencies determined that Type IIR surgical masks reduced detectable aerosol by 90%. Surgical masks wrapped around straws reduced detectable aerosol by 96%. HMEF filters were 100% effective in mitigating the aerosol from WRT, the exercise that generated more aerosol than any other task in the unmitigated condition. Voice therapy and assessment causes the release of significant quantities of respirable aerosol. However, simple mitigation strategies can reduce emitted aerosol concentrations to levels comparable to unmasked breathing.

Application of nanotechnology in air purifiers as a viable approach to protect against Corona virus.

The outbreak of COVID-19 disease, the cause of severe acute respiratory syndrome, is considered a worldwide public health concern. Although studies indicated that the virus could spread through respiratory particles or droplets in close contact, current research have revealed that the virus stays viable in aerosols for several hours. Numerous investigations have highlighted the protective role of air purifiers in the management of COVID-19 transmission, however, there are still some doubts regarding the efficiency and safety of these technologies. According to those observations, using a proper ventilation system can extensively decrease the spread of COVID-19. However, most of those strategies are currently in the experimental stages. This review aimed at summarising the safety and effectiveness of the recent approaches in this field including using nanofibres that prevent the spread of airborne viruses like SARS-CoV-2. Here, the efficacy of controlling COVID-19 by means of combining multiple strategies is comprehensively discussed.

Dissolving Microneedles Loaded with Nanoparticle Formulation of Respiratory Syncytial Virus Fusion Protein Virus-like Particles (F-VLPs) Elicits Cellular and Humoral Immune Responses.

Respiratory syncytial virus (RSV) is one of the leading causes of bronchiolitis and pneumonia in children ages five years and below. Recent outbreaks of the virus have proven that RSV remains a severe burden on healthcare services. Thus, a vaccine for RSV is a need of the hour. Research on novel vaccine delivery systems for infectious diseases such as RSV can pave the road to more vaccine candidates. Among many novel vaccine delivery systems, a combined system with polymeric nanoparticles loaded in dissolving microneedles holds a lot of potential. In this study, the virus-like particles of the RSV fusion protein (F-VLP) were encapsulated in poly (D, L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). These NPs were then loaded into dissolving microneedles (MNs) composed of hyaluronic acid and trehalose. To test the in vivo immunogenicity of the nanoparticle-loaded microneedles, Swiss Webster mice were immunized with the F-VLP NPs, both with and without adjuvant monophosphoryl lipid A (MPL) NPs loaded in the MN. The mice immunized with the F-VLP NP + MPL NP MN showed high immunoglobulin (IgG and IgG2a) levels both in the serum and lung homogenates. A subsequent analysis of lung homogenates post-RSV challenge revealed high IgA, indicating the generation of a mucosal immune response upon intradermal immunization. A flowcytometry analysis showed high CD8+ and CD4+ expression in the lymph nodes and spleens of the F-VLP NP + MPL NP MN-immunized mice. Thus, our vaccine elicited a robust humoral and cellular immune response in vivo. Therefore, PLGA nanoparticles loaded in dissolving microneedles could be a suitable novel delivery system for RSV vaccines.

Influence of two-dimensional expiratory airflow variations on respiratory particle propagation during pronunciation of the fricative [f

Propagation of respiratory particles, potentially containing viable viruses, plays a significant role in the transmission of respiratory diseases (e.g., COVID-19) from infected people. Particles are produced in the upper respiratory system and exit the mouth during expiratory events such as sneezing, coughing, talking, and singing. The importance of considering speaking and singing as vectors of particle transmission has been recognized by researchers. Recently, in a companion paper, dynamics of expiratory flow during fricative utterances were explored, and significant variations of airflow jet trajectories were reported. This study focuses on respiratory particle propagation during fricative productions and the effect of airflow variations on particle transport and dispersion as a function of particle size. The commercial ANSYS-Fluent computational fluid dynamics (CFD) software was employed to quantify the fluid flow and particle dispersion from a two-dimensional mouth model of sustained fricative [f] utterance as well as a horizontal jet flow model. The fluid velocity field and particle distributions estimated from the mouth model were compared with those of the horizontal jet flow model. The significant effects of the airflow jet trajectory variations on the pattern of particle transport and dispersion during fricative utterances were studied. Distinct differences between the estimations of the horizontal jet model for particle propagation with those of the mouth model were observed. The importance of considering the vocal tract geometry and the failure of a horizontal jet model to properly estimate the expiratory airflow and respiratory particle propagation during the production of fricative utterances were emphasized.

Assessment of Mask Effectiveness to Prevent the Spread of SARS-Cov-2: A Review

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus diseases 2019 (COVID-19) is mainly spread person-to-person through droplets and aerosols. It is often recommended that healthcare workers and other people take precautionary measures to reduce their exposure to SARS-CoV-2 by wearing masks. However, the effectiveness of the masks is not well understood at the community level. Methods: To assess the effectiveness of the masks against the SARS-CoV-2 virus, we searched electronic databases (Pubmed, Scopus, and Web of Science) for studies that assessed mask or respirator effectiveness in the prevention of SARS-CoV-2 transmission. Results: The majority of studies reviewed suggested that all types of masks (e.g., N95 respirators, surgical masks, and cloth masks) protect the human respiratory system against airborne viral pathogens, such as SARS-CoV-2. The quality and effectiveness of the masks vary depending on the materials, structures, and methods used for construction. The data shows that both surgical masks and N95 respirators can provide similar protection against airborne respiratory infections, including SARS-CoV-2, for healthcare workers, but due to its better facial fit, N95 is recommended for high-risk environments. However, although masks reduce the spread of SARS-CoV-2, they may not entirely provide proper protection against biologic particles, which are considerably smaller than the accepted most penetrating particle size used in certification tests. Conclusion: While all types of masks have technical pros and cons, wearing them correctly can significantly improve their effectiveness since a complete seal of respiratory particles is unlikely due to side leakage of aerosols of different sizes.