Effectiveness of RANS in predicting indoor airborne viral transmission: A critical evaluation against LES

We investigate the dispersal of droplet nuclei inside a canonical room of size 10×10×3.2m3 with a four-way cassette air-conditioning unit placed at the center of the ceiling. We use Reynolds averaged Navier–Stokes (RANS) simulations with three flow rates corresponding to air changes per hour (ACH) values of 2.5, 5, and 10. The room setup as well as the operating conditions are chosen to match those of a recent high-fidelity large eddy simulation (LES) study. We use statistical overloading with a total of one million droplet nuclei being initially distributed randomly with uniform probability within the room. Six nuclei sizes are considered ranging in radius from 0.1 to 10μm (166,667 nuclei per size). The simulations are one-way coupled and employ the Langevin equations to model sub-grid motion. The flow and particle statistics are compared against the reference LES simulations, and we find that the RANS k−ɛ realizable model may be used as a computationally cheaper alternative to LES for predicting pathogen concentration in confined spaces albeit, with potentially increased statistical discrepancy. © 2023 Elsevier Ltd

Management skills and digital transition for Mipymes Zone 3-Ecuador

After the Covid-19 pandemic, companies have faced a challenge in their economic activities, especially in the profile of human resources. The main objective of this research was to diagnose the managerial competencies of FMCG MSMEs in Zone 3-Ecuador necessary for a digital transition during the post-pandemic period. It is conceived as a descriptive study, with a prospective approach that used a structured survey for data collection, focused on a sample of 371 MSMEs in zone 3. Statistical tools were used for a quantitative analysis. In the results, two sections are presented, the first one focused on the diagnosis of the current situation of the companies, and the second one aligned to a statistical analysis where it was proved that managerial competences influence an adequate digital transition. It is concluded that it was evidenced that these are of vital importance because they support the improvement of the preparation and knowledge that both management and operational personnel possess;as well as, to face the challenges in the face of unexpected events. © 2023, Universidad del Zulia. All rights reserved.

Scintigraphic Patterns In Planar Pulmonary Perfusion-Only Studies In Patients With Dyspnea and Clinical Suspicion of COVID-19 Infection

Aim/Introduction: The purpose of this study is to perform a descriptive analysis of the scintigraphic patterns in pulmonary perfusion studies in patients with COVID-19 clinical suspicion, and its relation with biological (PCR positiviy) and biochemical parameters (D dimer plasmatic levels (DD)) as well as the presence of comorbidities. Material(s) and Method(s): 84 patients (44 male: 52.4% and 40 female: 47.6%, mean age: 68.08+/-15.85), either outpatients or hospitalized, with clinical COVID-19 suspicion, with conduction of the study from the onset of symptoms to even 19 months after it, in case of clinical persistence, and their pulmonary perfusion studies have been analyzed by three nuclear medicine physicians. The different patterns observed have been categorized in homogeneous, heterogeneous and segmental, and independence test have been run, by means of Chi square test (X2) or Fisher's exact test (FET), to detect a possible association of the latter with laboratory confirmation of COVID-19 infection, DD plasmatic levels (normal: <500ng/ml, high: 500-1.000ng/ ml, and very high:>1.000ng/ml) and the absence or presence of comorbidity (pulmonary disease, cardiovascular disease or both).Odds Ratio (OR) calculation has been run to estimate the probability of presenting a heterogeneous scintigraphic pattern in COVID infected vs. not infected patients, as well as in patients with very high vs. high DD levels. Result(s): Different scintigraphic patterns (31% homogeneous, 58.3% heterogeneous or 10,7% segmental) have been observed in patients with suspected COVID-19, of whom 65.5% were confirmed cases. Independence tests showed association between scintigraphic perfusion patterns and COVID-19 confirmation [X2= 8.0, p<0.05, Phi=0,324], while it did not in relation to DD levels [FET= 2.74, p>0.05]. The relative risk of presenting a heterogeneous scintigraphy in COVID+ patients is 0.16 ([0.043-0.595] %95 CI), thus infection can be considered a mild protector factor for heterogeneity. With regard to absence of previous disease (27.4%) or presence of pulmonary (4.8%), cardiac (57.1%) or coexistence of both diseases (10.7%), no significant association to the scintigraphic pattern could be found (chi2= 7.511, p>0.05]). Conclusion(s): Different scintigraphic patterns in pulmonary perfusion studies have been observed in patients with COVID-19 suspicion, being the heterogeneous one remarkably more frequent. It is significantly associated to positive microbiological test results but not to plasmatic DD levels or presence of comorbidity. Covid-infected patients have lower probability of presenting a heterogeneous scintigraphy pattern than not infected ones.

Sensitivity of puff dynamics and airborne droplet nuclei distribution to variations in violent expiration events

We use large eddy simulations to investigate the puff and droplet dynamics from violent expiratory events such as coughs and sneezes in the first few seconds following an ejection. For each of the eleven simulations considered, over 60,000 droplets are ejected and individually tracked using the point-particle Euler–Lagrange approach. We test the sensitivity of the puff and droplet dynamics to various parameters including the ejection volume, momentum, and orientation. We also explore the effect of the mouth shape on the aforementioned dynamics by considering elliptical and circular inlet cross-sections. The results from the simulations compare favorably with a recent theoretical framework put forth by Balachandar et al. (2020) in terms of the puff size and propagation velocity. More importantly however, the theory is able to accurately predict the number and size spectra of the potentially virus-laden droplet nuclei that remain airborne within the puff. We observe that the ejection angle and mouth shape do not significantly affect the puff and droplet dynamics. Additionally, we quantify the carrying capacity of the detached puff portions in terms of the number and size spectra of droplets/droplet nuclei suspended within. © 2022 Elsevier Ltd

Management skills and digital transition for Mipymes Zone 3-Ecuador

After the Covid-19 pandemic, companies have faced a challenge in their economic activities, especially in the profile of human resources. The main objective of this research was to diagnose the managerial competencies of FMCG MSMEs in Zone 3-Ecuador necessary for a digital transition during the post-pandemic period. It is conceived as a descriptive study, with a prospective approach that used a structured survey for data collection, focused on a sample of 371 MSMEs in zone 3. Statistical tools were used for a quantitative analysis. In the results, two sections are presented, the first one focused on the diagnosis of the current situation of the companies, and the second one aligned to a statistical analysis where it was proved that managerial competences influence an adequate digital transition. It is concluded that it was evidenced that these are of vital importance because they support the improvement of the preparation and knowledge that both management and operational personnel possess;as well as, to face the challenges in the face of unexpected events. © 2023, Universidad del Zulia. All rights reserved.

Effect of Vaccination on Household Transmission of SARS-CoV-2

Background. Understanding how COVID-19 vaccination affects transmission of SARS-CoV-2 within households may affect policy and healthcare decisions. We hypothesized that vaccination reduces transmission and viral load in vaccinated household members. Methods. We prospectively enrolled participants during March 2020 - October 2021. Index cases (IC) were eligible if they tested positive for SARS-CoV-2 within the previous 10 days and did not have household contacts (HC) who had tested positive or had symptoms of COVID-19. Participants self-collected anterior nares swabs daily for SARS-CoV-2 RT-PCR for at least 21 days, or once every member of the household had 7 consecutive negative tests. Baseline data included demographics and self-reported vaccination status. Complete COVID-19 vaccination was defined as receiving 2 doses of Moderna/Pfizer or 1 dose of Johnson & Johnson vaccine, and incomplete vaccination as receiving 1 dose of Moderna/Pfizer vaccine. Household transmission was analyzed via STATA 14.2 using logistic regression with robust standard error clustered by household, and SARS-CoV-2 cycle threshold was graphed by day of study enrollment using lowess smoothing. Results. There were 60 households with positive ICs and 103 HCs for a total of 163 participants. ICs had median age 41.5 years (range 1-86) with 9 (18.0%) < 18 years. HCs had median age 34 years (range 0-87) with 32 (31.1%) HCs < 18 years. Overall, 33 (20.2%) participants received at least one COVID-19 vaccine dose. A total of 50 households had at least one HC (median 2, max 7). Transmission of SARS-CoV-2 occurred in 45 HCs (43.7%). Odds of SARS-CoV-2 transmission was lower in HCs who were vaccinated prior to study enrollment, though this finding was not statistically significant (Table 1). There were 507 positive SARS-CoV-2 tests collected among 74 participants (Figure 1). Completely vaccinated: Received primary COVID-19 vaccination series (2 doses Pfizer or Moderna vaccine, or 1 dose Johnson & Johnson vaccine) prior to enrollment Conclusion. Vaccination of HCs may be protective against household SARS-CoV-2 transmission. However, analyses were limited due to low numbers of vaccinated study participants. Study enrollment is ongoing, and future analyses will include transmission during the 2022 Omicron surge, and daily symptom data which has been collected.

Use of a SARS-CoV-2 Strand-specific Assay to evaluate for Prolonged Viral Replication among Hospitalized Patients. Tertiary Care Center, California 2020- 2022

Background. Determining if a patient with SARS-CoV-2 remains infectious is an infection control challenge in healthcare settings;specially, among critically ill or profoundly immunosuppressed patients. We use an assay that detects minus-strand RNA as a surrogate for actively replicating SARS-CoV-2. We report positive strand-specific assays in relationship to time since admission and describe patients with a detectable strand-specific assay >20 days since admission. Methods. We use a 2-step rRT-PCR specific to the minus strand of the SARS-CoV-2 envelope gene. The strand-specific assay is used to evaluate for infectivity in asymptomatic patients with a positive admission screening or pre-procedural test or if ongoing replication is suspected (critical illness or profound immunosuppression). We retrieved strand-specific test results for patients hospitalized at Stanford Healthcare during August 2020-March 2022. We describe clinical characteristics for patients with a detectable minus strand-specific test >20 days since admission. Results. A total of 774 strand-specific tests were collected from 624 hospitalized patients. A total of 523 patients had only one test (84%) and 101 (16%) had >=2 tests. The test positivity rate varied by time since admission: 19% in tests performed 0-5 days, 28% in 6-10 days, 22% in 11-20 days, and 41% in those >20 days since admission. Among 35 patients tested >20 days since admission, 13 (37%) had >=1 detectable minus strand-specific test. Most were male (n=8, 62%) and mean age was 59. Of 13 patients with a detectable assay, seven (54%) had prolonged viral replication with persistent symptoms and detectable minus strand assays for >20 days from symptom onset. Of these seven patients, four had a transplant (3 lung, 1 liver), 1 ovarian cancer, 1 CAR-T cell therapy, and 1 ESRD without immunosuppression. The remaining eight patients with a detectable assay >20 days since admission had illness onset while hospitalized. Conclusion. Among hospitalized patients with SARS-CoV-2 infection, we found a varying positivity rate according to the timing of testing, possibly reflecting different indications for the test. The strand-specific assay may help assess for infectiousness in profoundly immunocompromised patients.

Lack of SARS-CoV-2 transmission from a Healthcare Worker to a Cohort of Immunosuppressed Patients during the Omicron Surge, California, 2022

Background. The Omicron surge caused a significant strain on the healthcare system, particularly as it relates to healthcare worker (HCW) infections. Occult infection transmission from HCWs to patients is an important area upon which infection control programs can continue to improve. Methods. We conducted a retrospective chart review of 9 patients on the immunocompromised solid organ transplant service who were exposed to a highly infectious vaccinated and boosted healthcare worker across 2 days during the Omicron surge in January 2022. Results. The index healthcare worker began to show symptoms shortly after rounds on the second day of clinical service. Nasopharyngeal rtPCR testing for SARS CoV 2 was positive, Ct value 15.9;a routine screening Covid19 test the day prior using an anterior nares swab had been negative. All 9 patients who were exposed and received follow-up testing on days 3-5 since exposure were negative for SARS CoV 2. One additional healthcare worker who was also exposed tested negative on followup testing despite several hours of close contact across 2 days. Both HCWs wore N95 respirators during all patient care and in breakrooms. Patient exposures were less than 15 minutes in duration, but also less than 6 feet in distance. Conclusion. The index healthcare worker did not transmit SARS CoV 2 to a cohort of immunocompromised patients or to a fellow HCW despite being very infectious. The index HCW wore an N95 respirator during all patient encounters which could have reduced the chance for transmission.

Use of a SARS-CoV-2 Strand-specific Assay to detect Relapse or Ongoing Infection at a Tertiary Care Center, California 2020-2022

Background. Determining if a patient with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains infectious can be challenging in patients with severe disease or those profoundly immunosuppressed. We use an assay that detects minus-strand RNA as a surrogate for actively replicating SARS-CoV-2. Here, we describe a cohort of patients who had strand-assay reversion: a detectable minus strandspecific assay after having had an undetectable value which may signify relapse of infection or reinfection. Methods. We used a 2-step rRT-PCR specific to the minus strand of the SARS-CoV-2 envelope gene. The strand-specific assay is used to evaluate for infectivity in asymptomatic patients with a positive screening admission or pre-procedural test or in cases when ongoing infection was suspected (critical illness or profound immunosuppression). We collected minus strand-specific assays performed at Stanford Healthcare during August 2020-April 2022. We describe basic demographics and clinical characteristics for patients who reverted from undetectable to detectable using the minus strand-specific assay. Results. A total of 2,505 strand-specific tests were collected from August 2020-April 2022 from 2,064 patients. A total of 292 (14%) had two or more strandspecific tests. Of them, 19 (7%) had an undetected minus strand-specific assay followed by a subsequent detectable value. Of them, seven (37%) had a minus strandspecific CT value of < 33.Most were male (n=4), median age was 54 (range: 8-62). All were profoundly immunosuppressed: Four had hematologic malignancies and three were post transplantation (kidney, lung, bone marrow). Median time from onset of symptoms or first positive test to reversion was 41 days (range:27-159). Median time from undetectable to detectable minus strand specific test was 26 days (range:4-34). All cases were considered relapses or ongoing infection rather than a new infection. Conclusion. Among patients with SARS-CoV-2 infection and consecutive strand-specific testing, a small proportion reverted from negative to positive. Most were profoundly immunosuppressed. The strand-specific assay can be an important tool in the evaluation of suspected cases of relapse or reinfection.

ON THE EJECTION SCALE PROBLEM OF EXPIRATORY EVENTS FROM THEORY AND SIMULATIONS

The overall purpose of this study is to investigate expiratory events such as coughs and sneezes in the ejection scale framework, i.e. within a short time span immediately after the expiration process. We conducted large eddy simulations (LES) and compared the results with a recent theoretical model put forth by Balachandar et al. [2]. The theoretical model [2] has been formulated to estimate the evolution of expiratory events such as coughs and sneezes. Some of the key features of the model include estimates for the time evolution of the puff centroid, its size, as well as the number and size of droplets suspended within. The theoretical model includes closure parameters that have been obtained from LES [6, 7]. The simulations cover a wide range of parameters, such as the ejection volume of the puff, its momentum, the ejection angle (whether horizontal, inclined, or vertical), and the ambient humidity. One of the important findings is that while certain aspects such as the front-most location and the lateral extent of the puff, show large variability from one realization to the other, global parameters, such as the centroid location, total volume, and buoyancy show are much less sensitive to turbulent fluctuations. The results also indicate that humid ambient conditions favor stronger gravitational settling of the ejected virus-laden droplets, thus decreasing the risk of infection from the dominant airborne route. Furthermore, the simulations highlight a mechanism for transporting a relatively large amount of droplets over distances upward of 2 meters in a time span on the order of one second. This mechanism, which is also observed in experiments, consists of fast moving detached vortex rings that propagate in a seemingly random direction. We further quantify the size and viral content of the detached portions. © 2022 Begell House Inc.. All rights reserved.

Corowa-kun: Impact of a COVID-19 Vaccine Information Chatbot on Vaccine Hesitancy, Japan 2021

Background. Japan has one of the highest vaccine hesitancy rates in the world. According to a previous study, less than 30% of people strongly agreed that vaccines were safe, important, or effective. We created a COVID-19 vaccine information chatbot in a popular messenger app in Japan to answer COVID-19 vaccine frequently asked questions (FAQs) via text messages. We assessed the impact of chatbot text messages on COVID-19 vaccine hesitancy by conducting a cross-sectional survey among chatbot users. Methods. LINE is the most popular messenger app in Japan;about 86 million people in Japan (roughly two-thirds of the population) use this messenger app. Corowa-kun, a free chatbot, was created in LINE on February 6, 2021. Corowa-kun provides instant, automated answers to frequently asked COVID-19 vaccine questions. A cross-sectional survey assessing COVID-19 vaccine hesitancy was conducted via Corowa-kun during April 5 to 12, 2021. We included persons ages 16 years old and older who had not received a COVID-19 vaccine. The survey was written in Japanese and consisted of 21 questions. Corowa-kun is the mascot of an online chatbot. This chatbot in LINE is used to answer COVID-19 vaccine frequently asked questions (FAQs) via text messages. As of May 10th, 70 FAQs are available. Results. A total of 59,676 persons used Corowa-kun during February to April 2021. The most commonly accessed message categories were: "I have (select comorbidity), can I get a COVID-19 vaccine?" (23%);followed by questions on adverse reactions (22%) and how the vaccine works (20%). 10,192 users (17%) participated in the survey. Median age was 55 years (range 16 to 97), and most were female (74%). Intention to receive a COVID-19 vaccine increased from 59% to 80% after using Corowa-kun (p < 0.01). Overall, 20% remained hesitant: 16% (1,675) were unsure, and 4% (364) did not intend to be vaccinated. Factors associated with vaccine hesitancy were: age 16 to 34 (odds ratio [OR] = 3.7, 95% confidential interval [CI]: 3.0-4.6, compared to age ≥65), female sex (OR = 2.4, Cl: 2.1-2.8), and history of another vaccine side-effect (OR = 2.5, Cl: 2.2-2.9). Being a physician (OR = 0.2, Cl: 0.1-0.4) and having received a flu vaccine the prior season (OR = 0.4, Cl: 0.3-0.4) were protective. COVID-19 vaccine acceptance increased and hesitancy decreased after using Corowa-kun, Japan, 2021 (n=10,192) ∗There was a statistically significant difference in responses between before and after using Corowa-kun (p < 0.01, Chi-square test). Univariable logistic regression models of factors associated with COVID-19 vaccine hesitancy, Japan, 2021 (n=10,192) Ref: reference NA: Logistic regression was not performed due to too small number (n≤3) Conclusion. Corowa-kun reduced vaccine hesitancy by providing COVID-19 vaccine information in a messenger app. Mobile messenger apps could be leveraged to increase COVID-19 vaccine acceptance.

Asymptomatic Pre-Operative COVID-19 Screening for Essential and Elective Surgeries: Early Results of Universal Screening at a Midwestern Academic Medical Center

Background: During the novel Coronavirus 2019 (COVID-19) worldwide pandemic, viral testing has largely focused on patients presenting with fever and respiratory symptoms. Although Centers for Disease Control has reported 1,551,095 cases in the United States as of May 21, 2020, asymptomatic infection rates remain unknown within the U.S., especially in geographically disparate regions. Methods: On April 7, 2020 our hospital established universal SARS-CoV-2 screening using RT-PCR RNA detection from nasopharyngeal swabs from asymptomatic patients prior to essential and elective surgeries. This study included 1,997 asymptomatic patients undergoing surgical procedures and 1,797 admitted for medical management at a Midwestern academic hospital between April 7, 2020 and May 21, 2020. Results: As of May 21, asymptomatic testing for SARS-CoV-2 infection had been completed for 1,997 surgical patients and 1,797 non-surgical patients. Initial testing was positive in 26 patients, with an additional four positive tests occurring during repeat testing when greater than 48 hours had elapsed since initial testing. Overall asymptomatic infection rate was 0.79%. Asymptomatic infection rate was significantly lower in surgical patients (0.35% vs. 1.28%, p=0.001). Surgical patients tended to be older than non-surgical patients, although this was not statistically significant (51, IQR 27-65 vsx 46, IQR 28-64, p=0.057). Orthopedic surgery patients were significantly younger than those from other surgical services (42 vs. 53 yrs, p<0.001), however orthopedic and non-orthopedic surgical patients had similar asymptomatic infection rates (0.70% vs. 0.25%, p=0.173). Conclusion: Among asymptomatic patients tested at a Midwestern academic medical center, 0.79% were infected with SARS-CoV-2 virus. These findings will help guide screening protocols at medical centers while providing essential and elective procedures during the COVID-19 pandemic. While the asymptomatic infection rate was low, this data substantiates the threat of asymptomatic infections and potential for community viral spread. These results may not be generalizable to large urban population centers or areas with high concentrations of COVID-19, each region must use available data to evaluate the risk-benefit ratio of universal testing vs universal contact precautions. Level of Evidence: IV.