Numerical simulation of social distancing of preventing airborne transmission in open space with lateral wind direction, taking into account temperature of human body and floor surface.

This paper presents the numerical results of particle propagation in open space, taking into account the temperature of the human body and the surface of the ground. And also, the settling of particles or droplets under the action of gravitational force and transport in the open air is taken into account, taking into account the temperature during the process of breathing and sneezing or coughing. The temperature of the body and the surface of the ground, different rates of particle emission from the mouth, such as breathing and coughing or sneezing, are numerically investigated. The effect of temperature, cross-inlet wind, and the velocity of particle ejection from a person's mouth on social distancing is being investigated using a numerical calculation. The variable temperature of the human body forms a thermal plume, which affects the increase in the trajectory of the particle propagation, taking into account the lateral air flow. The thermal plume affects the particles in the breathing zone and spreads the particles over long distances in the direction of the airflow. The result of this work shows that in open space, taking into account the temperature of the body and the surface of the ground, a 2-m social distance may be insufficient for the process of sneezing and social distance must be observed depending on the breathing mode.

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.

Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread.

Effects of indoor temperature (T∞) and relative humidity (RH∞) on the airborne transmission of sneeze droplets in a confined space were studied over the T∞ range of 15-30 °C and RH∞ of 22-62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH∞,crit of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T∞. At RH∞ < RH∞,crit, the sneezing jet velocity decreased by increasing T∞ from 15 to 30 °C, while its trend was reversed at RH∞ > RH∞,crit. The maximum spreading distance of aerosols increased by decreasing the RH∞ and increasing T∞, while the droplet lifetime increased by decreasing T∞ at RH∞ > RH∞,crit. The mean diameter of aerosolized droplets was less affected by T∞ than the large droplets at RH∞ < RH∞,crit, while the mean diameter and number fraction of aerosols were more influenced by RH∞ than the T∞ in the range of 46% ≤ RH∞ ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19.

Are elderly people exhibiting greater sensitivity to the nature of communication due to sneezing and nasal discharge?

OBJECTIVE: Communication with elderly has always presented specific challenges which do not affect other groups. The aim of the study was to investigate how elderly patients perceive communication with doctors due to sneezing and nasal discharge, in particular during COVID-19 pandemic having personal protective equipment, including goggles, face shield, mask and hazard suits affects the quality of communication. SUBJECTS AND METHODS: 100 patients (50 male and 50 female), all over the age of 65 years, were enrolled as the study group. Elderly patients attending the otorhinolaryngology department, for any reason, were invited to participate in the study, which was carried out during the COVID-19 pandemic. A control group, consisting of 50 patients (male and female), and aged between 25 and 35 years, was also recruited in the same way. Communication questionnaire and Social Communication Skills Rating Scale were applied to all participants. RESULTS: The results indicate that patients sneezing, with nasal discharge symptoms, and doctors' use of personal protective equipment, including goggles, facial shields, masks and hazard suits and the precautions in behavior designed to protect the doctor during the COVID-19 pandemic were associated with negative effects on doctor-patient communication. CONCLUSIONS: It is a cultural expectation that seniors be invariably treated with respect. In the extraordinary circumstances of the current pandemic, clinicians need to pay even more attention than usual to how they communicate, to ensure that communication remains both effective and respectful at all times.

Effect of indoor temperature on the velocity fields and airborne transmission of sneeze droplets: An experimental study and transient CFD modeling.

The spread of the COVID-19 pandemic through the airborne transmission of coronavirus-containing droplets emitted during coughing, sneezing, and speaking has now been well recognized. This study presented the effect of indoor temperature (T∞) on the airflow dynamics, velocity fields, size distribution, and airborne transmission of sneeze droplets in a confined space through experimental investigation and computational fluid dynamic (CFD) modeling. The CFD simulations were performed using the renormalization group k-ε turbulence model. The experimental shadowgraph imaging and CFD simulations showed the time evolution of sneeze droplet concentrations into the turbulent expanded puff, droplet cloud, and fully-dispersed droplets. Also, the predicted mean velocity of droplets was compared with the obtained experimental data to assess the accuracy of the results. In addition, the validated computational model was used to study the sneeze complex airflow behavior and airborne transmission of small, medium, and large respiratory droplets in confined spaces at different temperatures. The warm room showed more than ∼14 % increase in airborne aerosols than the room with a mild temperature. The study provides information on the effect of room temperature on the evaporation of respiratory droplets during sneezing. The findings of this fundamental study may be used in developing exposure guidelines by controlling the temperature level in indoor environments to reduce the exposure risk of COVID-19.

Assessment of the frequency of coughing and sneezing triggered by nasopharyngeal swabbing in the pandemic setting.

A variety of medical procedures are classified as aerosol generating. However there is no consensus on whether some procedures such as nasopharyngeal swabbing can generate aerosols. During specimen collection, the contact of the nasopharyngeal swab with the respiratory mucosa often triggers defense reflexes such as sneezing and coughing, which generate airborne particles. The accumulation and persistence of a viral load from infectious aerosols for hours after their generation can represent a threat for increased spread of infection. Prospective observational cohort study in individuals tested for RT-PCR SARS-CoV-2 from July to October 2020. Participants were evaluated for the prevalence of aerosol generating events (AGEs) triggered by the nasopharyngeal swabbing. We used descriptive statistics to analyze the data set and the chi-square test for AGE comparison between sexes. Among 1239 individuals, we reported 264 in which AGEs were triggered by the specimen collection. 97 individuals tested positive for SARS-CoV-2, of which 20 presented AGEs. There were no significant differences in the occurrence of AGEs by age, but significant differences have been identified between sex and the occurrence of AGEs both in the SARS-CoV-2 negative and SARS-CoV-2 positive individuals. The prevalence of coughing or sneezing triggered by the nasopharyngeal swabbing was high among tested individuals. Testing facilities should ensure adequate availability of personal protective equipment (PPE) for the testing personnel, ensure appropriate ventilation of the rooms, and develop additional strategies to limit the risk of contamination of other participants to the testing session from potentially infectious and persistent aerosols.

Numerical investigation on indoor environment decontamination after sneezing.

More than 320 million people worldwide were affected by SARS-CoV-2 or COVID-19, which already caused more than 5.5 million deaths. COVID-19 spreads through air when an infected person breathes, coughs, or sneezes out droplets containing virus. Emerging variants like Omicron with positivity rate of 16 (highest among others) present a greater risk of virus spread, so all types of indoor environments become critically important. Strategically adopted Heating Ventilation and Air Conditioning (HVAC) approach can significantly reduce the virus spread by early removal of contaminated aerosolized droplets. We modeled different HVAC configurations to characterize the diffusion of contaminated droplets cloud through Computational Fluid Dynamics (CFD) simulations of sneeze in standard hospital room as indoor scenario. Injection of saliva droplets with characteristics of exhaled air from lungs was applied to mimic real sneeze. CFD simulations have been performed for three HVAC configurations at two Air Change per Hour (ACH) rates; 6 and 15 ACH. For the first time, use of air curtain at low flow rate has been examined. Simulations provide high fidelity spatial and temporal droplets cloud diffusion under different HVAC configurations, showing spread in room indoor environment up to 360 s. Over 92% of ejected sneeze mass is removed from room air within seconds while the remaining 8% or less becomes airborne with droplets (<50 µm size) and tends to spread uniformly with regular HVAC configuration. Low-speed air curtain accelerates decontamination by efficiently removing aerosolized 1-50 µm size droplets. Study investigates role of droplets removal mechanisms such as escape, evaporation, and deposition on surfaces. Interestingly, results show presence of contaminated droplets even after 5 min of sneeze, which can be effectively removed using low-speed air curtain. Study finds that high ventilation rate requirements can be optimized to modify earlier and new hospital designs to reduce the spread of airborne disease.

Assessment of airborne transmission from coughing processes with thermal plume adjacent to body and radiators on effectiveness of social distancing.

The new coronavirus disease COVID-19 has caused a worldwide pandemic to be declared in a very short period of time. The complexity of the infection lies in asymptomatic carriers that can inadvertently transmit the virus through airborne droplets. This kind of viral disease can infect the human body with tiny particles that carry various bacteria that are generated by the respiratory system of infected patients. In this study, numerical results are proposed that demonstrate the effect of human body temperature and temperature from radiators in a room on the spread of the smallest droplets and particles in an enclosed space. The numerical model proposed in this work takes into account the sedimentation of particles and droplets under the action of gravitational sedimentation and transport in a closed room during the processes of breathing, sneezing or coughing. Various cases were considered, taking into account normal human breathing, coughing or sneezing, as well as three different values of the rate of emission of particles from the human mouth. The heat plume, which affects the concentration of particles in the breathing zone, spreads the particle up to a distance of 4.29 m in the direction of the air flow. It can also be seen from the results obtained that the presence of radiators strongly affects the propagation of particles of various sizes in a closed room. From the obtained results, it should be noted that in order to recommend the optimal social distance, it is necessary to take into account many factors, especially momentum, gravity, human body temperature, as well as the process of natural convection, which greatly affect the propagation of particles in a closed room. The conclusions drawn from the results of this work show that, given the environmental conditions, the social distance of 2 m may not be enough.

Computational characterization of the behavior of a saliva droplet in a social environment.

The conduct of respiratory droplets is the basis of the study to reduce the spread of a virus in society. The pandemic suffered in early 2020 due to COVID-19 shows the lack of research on the evaporation and fate of droplets exhaled in the environment. The current study, attempts to provide solution through computational fluid dynamics techniques based on a multiphase state with the help of Eulerian-Lagrangian techniques to the activity of respiratory droplets. A numerical study has shown how the behavior of droplets of pure water exhaled in the environment after a sneeze or cough have a dynamic equal to the experimental curve of Wells. The droplets of saliva have been introduced as a saline solution. Considering the mass transferred and the turbulence created, the results has showed that the ambient temperature and relative humidity are parameters that significantly affect the evaporation process, and therefore to the fate. Evaporation time tends to be of a higher value when the temperature affecting the environment is lower. With constant parameters of particle diameter and ambient temperature, an increase in relative humidity increases the evaporation time. A larger particle diameter is consequently transported at a greater distance, since the opposite force it affects is the weight. Finally, a neural network-based model is presented to predict particle evaporation time.

Variations in human saliva viscoelasticity affect aerosolization propensity.

Some contagious diseases, such as COVID-19, spread through the transmission of aerosols and droplets. Aerosol and droplet formation occurs inside and outside of the respiratory tract, the latter being observed during speaking and sneezing. Upon sneezing, saliva is expelled as a flat sheet, which destabilizes into filaments that subsequently break up into droplets. The presence of macromolecules (such as mucins) in saliva influences the dynamics of aerosol generation, since elasticity is expected to stabilize both fluid sheets and filaments, hence deterring droplet formation. In this study, the process of aerosol formation outside the respiratory tract is systematically replicated using an impinging jet setup, where two liquid jets collide and form a thin fluid sheet that can fragment into ligaments and droplets. The experimental setup enables us to investigate a range of dynamic conditions, quantified by the relevant non-dimensional numbers, which encompass those experienced during sneezing. Experiments are conducted with human saliva provided by different donors, revealing significant variations in their stability and breakup. We quantify the effect of viscoelasticity via shear and extensional rheology experiments, concluding that the extensional relaxation time is the most adequate measure of a saliva's elasticity. We summarize our results in terms of the dimensionless Weber, Reynolds, and Deborah numbers and construct universal state diagrams that directly compare our data to human sneezing, concluding that the aerosolization propensity is correlated with diminished saliva elasticities, higher emission velocities, and larger ejecta volumes. This could entail variations in disease transmission between individuals which hitherto have not been recognized.

Expiratory aerosol particle escape from surgical masks due to imperfect sealing.

Wearing surgical masks or other similar face coverings can reduce the emission of expiratory particles produced via breathing, talking, coughing, or sneezing. Although it is well established that some fraction of the expiratory airflow leaks around the edges of the mask, it is unclear how these leakage airflows affect the overall efficiency with which masks block emission of expiratory aerosol particles. Here, we show experimentally that the aerosol particle concentrations in the leakage airflows around a surgical mask are reduced compared to no mask wearing, with the magnitude of reduction dependent on the direction of escape (out the top, the sides, or the bottom). Because the actual leakage flowrate in each direction is difficult to measure, we use a Monte Carlo approach to estimate flow-corrected particle emission rates for particles having diameters in the range 0.5-20 µm. in all orientations. From these, we derive a flow-weighted overall number-based particle removal efficiency for the mask. The overall mask efficiency, accounting both for air that passes through the mask and for leakage flows, is reduced compared to the through-mask filtration efficiency, from 93 to 70% for talking, but from only 94-90% for coughing. These results demonstrate that leakage flows due to imperfect sealing do decrease mask efficiencies for reducing emission of expiratory particles, but even with such leakage surgical masks provide substantial control.

The impact of surgical masks on the nasal function in the COVID-19 era.

BACKGROUND: The Covid-19 pandemics has obliged to using different types of personal protective devices (PPD) for a prolonged time of the day, especially in the Health Centers, with preference of surgical masks (SM) during the first pandemic waves. AIMS/OBJECTIVES: This study was designed to assess the eventual changes of the nasal respiratory condition during continuous SM wearing. MATERIAL AND METHODS: Fourteen healthcare professionals filled a visual analogue scale (VAS) questionnaire for the detection of eventual nasal breathing impairment or symptoms. Nasal resistance and flow values were obtained via the active anterior rhinomanometry (AAR) that was performed under the basal condition, as well as immediately after wearing the surgical mask (SM) and 3 h after its continuous use. RESULTS: The increase of inspiratory resistance was significantly correlated to the reduction of the maximum flux, when comparing SM parameters to the basal ones (r = -0.70, p < .05). At VAS evaluation, SM wearing showed to induce itching in 70% of the subjects, nasal dryness in 55%, nasal blockage in 50%, headache in 39%, watery nasal discharge in 20% and sneezing in 18%. CONCLUSIONS AND SIGNIFICANCE: The SMs do not induce evident physiological variations of the nasal function due to a compensatory respiratory mechanism that, despite a progressive increase of nasal resistances, is not inducing significant changes of the nasal fluxes.

Propagation of viral bioaerosols indoors.

Here we look into the spread of aerosols indoors that may potentially carry viruses. Many viruses, including the novel SARS-CoV-2, are known to spread via airborne and air-dust pathways. From the literature data and our research on the propagation of fine aerosols, we simulate herein the carryover of viral aerosols in indoor air. We demonstrate that a lot of fine droplets released from an infected person's coughing, sneezing, or talking propagate very fast and for large distances indoors, as well as bend around obstacles, lift up and down over staircases, and so on. This study suggests equations to evaluate the concentration of those droplets, depending on time and distance from the source of infection. Estimates are given for the safe distance to the source of infection, and available methods for neutralizing viral aerosols indoors are considered.

Effect of saliva fluid properties on pathogen transmissibility.

With an increasing body of evidence that SARS-CoV-2 is an airborne pathogen, droplet character formed during speech, coughs, and sneezes are important. Larger droplets tend to fall faster and are less prone to drive the airborne transmission pathway. Alternatively, small droplets (aerosols) can remain suspended for long time periods. The small size of SARS-CoV-2 enables it to be encapsulated in these aerosols, thereby increasing the pathogen's ability to be transmitted via airborne paths. Droplet formation during human respiratory events relates to airspeed (speech, cough, sneeze), fluid properties of the saliva/mucus, and the fluid content itself. In this work, we study the fluidic drivers (fluid properties and content) and their influence on factors relating to transmissibility. We explore the relationship between saliva fluid properties and droplet airborne transmission paths. Interestingly, the natural human response appears to potentially work with these drivers to mitigate pathogen transmission. In this work, the saliva is varied using two approaches: (1) modifying the saliva with colloids that increase the viscosity/surface tension, and (2) stimulating the saliva content to increased/decreased levels. Through modern experimental and numerical flow diagnostic methods, the character, content, and exposure to droplets and aerosols are all evaluated. The results indicate that altering the saliva properties can significantly impact the droplet size distribution, the formation of aerosols, the trajectory of the bulk of the droplet plume, and the exposure (or transmissibility) to droplets. High-fidelity numerical methods used and verify that increased droplet size character enhances droplet fallout. In the context of natural saliva response, we find previous studies indicating natural human responses of increased saliva viscosity from stress and reduced saliva content from either stress or illness. These responses both favorably correspond to reduced transmissibility. Such a finding also relates to potential control methods, hence, we compared results to a surgical mask. In general, we find that saliva alteration can produce fewer and larger droplets with less content and aerosols. Such results indicate a novel approach to alter SARS-CoV-2's transmission path and may act as a way to control the COVID-19 pandemic, as well as influenza and the common cold.

Shielding of viruses such as SARS-Cov-2 from ultraviolet radiation in particles generated by sneezing or coughing: Numerical simulations of survival fractions.

SARS-CoV-2 and other microbes within aerosol particles can be partially shielded from UV radiation. The particles refract and absorb light, and thereby reduce the UV intensity at various locations within the particle. Previously, we demonstrated shielding in calculations of UV intensities within spherical approximations of SARS-CoV-2 virions within spherical particles approximating dried-to-equilibrium respiratory fluids. The purpose of this paper is to extend that work to survival fractions of virions (i.e., fractions of virions that can infect cells) within spherical particles approximating dried respiratory fluids, and to investigate the implications of these calculations for using UV light for disinfection. The particles may be on a surface or in air. Here, the survival fraction (S) of a set of individual virions illuminated with a UV fluence (F, in J/m2) is assumed described by S(kF) = exp(-kF), where k is the UV inactivation rate constant (m2/J). The average survival fraction (Sp) of the simulated virions in a group of particles is calculated using the energy absorbed by each virion in the particles. The results show that virions within particles of dried respiratory fluids can have larger Sp than do individual virions. For individual virions, and virions within 1-, 5-, and 9-µm particles illuminated (normal incidence) on a surface with 260-nm UV light, the Sp = 0.00005, 0.0155, 0.22, and 0.28, respectively, when kF = 10. The Sp decrease to <10-7, <10-7, 0.077, and 0.15, respectively, for kF = 100. Results also show that illuminating particles with UV beams from widely separated directions can strongly reduce the Sp. These results suggest that the size distributions and optical properties of the dried particles of virion-containing respiratory fluids are likely important to effectively designing and using UV germicidal irradiation systems for microbes in particles. The results suggest the use of reflective surfaces to increase the angles of illumination and decrease the Sp. The results suggest the need for measurements of the Sp of SARS-CoV-2 in particles having compositions and sizes relevant to the modes of disease transmission.

Quantitative Microbial Risk Assessment for Airborne Transmission of SARS-CoV-2 via Breathing, Speaking, Singing, Coughing, and Sneezing.

BACKGROUND: Evidence for indoor airborne transmission of SARS-CoV-2 is accumulating. OBJECTIVES: We assessed of the risk of illness due to airborne SARS-CoV-2 particles from breathing, speaking, singing, coughing, and sneezing in indoor environments. METHODS: A risk assessment model, AirCoV2, for exposure to SARS-CoV-2 particles in aerosol droplets was developed. Previously published data on droplets expelled by breathing, speaking, singing, coughing, and sneezing by an infected person were used as inputs. Scenarios encompassed virus concentration, exposure time, and ventilation. Newly collected data of virus RNA copies in mucus from patients are presented. RESULTS: The expelled volume of aerosols was highest for a sneeze, followed by a cough, singing, speaking, and breathing. After 20 min of exposure, at 107 RNA copies/mL in mucus, all mean illness risks were largely estimated to be below 0.001, except for the "high" sneeze scenario. At virus concentrations above 108 RNA copies/mL, and after 2 h of exposure, in the high and "low" sneeze scenarios, the high cough scenario and the singing scenario, risks exceeded 0.01 and may become very high, whereas the low coughing scenario, the high and low speaking scenarios and the breathing scenario remained below 0.1. After 2 h of exposure, singing became the second highest risk scenario. One air exchange per hour reduced risk of illness by about a factor of 2. Six air exchanges per hour reduced risks of illness by a factor of 8-13 for the sneeze and cough scenarios and by a factor of 4-9 for the other scenarios. DISCUSSION: The large variation in the volume of expelled aerosols is discussed. The model calculations indicated that SARS-CoV-2 transmission via aerosols outside of the 1.5-m social distancing norm can occur. Virus concentrations in aerosols and/or the amount of expelled aerosol droplets need to be high for substantial transmission via this route. AirCoV2 is made available as interactive computational tool. https://doi.org/10.1289/EHP7886.

Natural nasal-esophageal fiberscopy in the COVID-19 pandemic-preventing sneezing without anesthesia: a case report.

BACKGROUND: We are laryngologists. We observe natural phonatory and swallowing functions in clinical examinations with a trans-nasal laryngeal fiberscope (TNLF). Before each observation, we use epinephrine to enlarge and smooth the common nasal meatus (bottom of nostril) and then insert a wet swab inside the nose, as in taking a swab culture in the nasopharynx. During the current COVID-19 pandemic situation, this careful technique prevents any complications, including nasal bleeding, painfulness, and induced sneezing. Here, we introduce our routine to observe esophageal movement in swallowing in a natural (sitting) position without anesthesia. CASE PRESENTATION: The case was a 70-year-old female who complained that something was stuck in her esophagus; there was a strange sensation below the larynx and pharynx. After enlarging and smoothing the common nasal meatus, we inserted the TNLF (slim type ⌀2.9 mm fiberscope, VNL8-J10, PENTAX Medical, Tokyo, Japan.) in the normal way. We then observed the phonatory and swallowing movements of the vocal folds. As usual, to not interfere with natural movements, we used no anesthesia. We found no pathological condition in the pyriform sinus. We asked the patient to swallow the fiberscope. During the swallow, we pushed the TNLF and inserted the tip a bit deeper, which made the fiberscope easily enter the esophagus, like in the insertion of a nasogastric tube. We then asked the patient to swallow a sip of water or saliva to clear and enlarge the lumen of the esophagus. This made it possible to observe the esophagus easily without any air supply. With tone enhancement scan, the esophagus was found to be completely normal except for glycogenic acanthosis. CONCLUSIONS: The advantage of this examination is that it is easily able to perform without anesthesia and with the patient in sitting position. It is quick and minimally invasive, enabling observation the physiologically natural swallowing. It is also possible to observe without anesthesia down to the level of the esophagogastric junction using with a thin type flexible bronchoscope. In the future, gastric fiberscopes might be thinner, even with narrow band imaging (NBI) function. Before that time, physicians should remember to just insert along the bottom of the nose.