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Evidence varies as to how far aerosols spread from individuals infected with SARS-CoV-2 in hospital rooms. We investigated the presence of aerosols containing SARS-CoV-2 inside of dedicated COVID-19 patient rooms. Three National Institute for Occupational Safety and Health BC 251 two-stage cyclone samplers were set up in each patient room for a six-hour sampling period. Samplers were place on tripods, which each held two samplers at various heights above the floor. Extracted samples underwent reverse transcription polymerase chain reaction for selected gene regions of the SARS-CoV-2 virus nucleocapsid. Patient medical data were compared between participants in rooms where virus-containing aerosols were detected and those where they were not. Of 576 aerosols samples collected from 19 different rooms across 32 participants, 3% (19) were positive for SARS-CoV-2, the majority from near the head and foot of the bed. Seven of the positive samples were collected inside a single patient room. No significant differences in participant clinical characteristics were found between patients in rooms with positive and negative aerosol samples. SARS-CoV-2 viral aerosols were detected from the patient rooms of nine participants (28%). These findings provide reassurance that personal protective equipment that was recommended for this virus is appropriate given its spread in hospital rooms.

Indoor superspreading events are significant drivers of transmission of respiratory diseases. In this work, we study the dynamics of airborne transmission in consecutive meetings of individuals in enclosed spaces. In contrast to the usual pairwise-interaction models of infection where effective contacts transmit the disease, we focus on group interactions where individuals with distinct health states meet simultaneously. Specifically, the disease is transmitted by infected individuals exhaling droplets (contributing to the viral load in the closed space) and susceptible ones inhaling the contaminated air. We propose a modeling framework that couples the fast dynamics of the viral load attained over meetings in enclosed spaces and the slow dynamics of disease progression at the population level. Our modeling framework incorporates the multiple time scales involved in different setups in which indoor events may happen, from single-time events to events hosting multiple meetings per day, over many days. We present theoretical and numerical results of trade-offs between the room characteristics (ventilation system efficiency and air mass) and the group’s behavioral and composition characteristics (group size, mask compliance, testing, meeting time, and break times), that inform indoor policies to achieve disease control in closed environments through different pathways. Our results emphasize the impact of break times, mask-wearing, and testing on facilitating the conditions to achieve disease control. We study scenarios of different break times, mask compliance, and testing. We also derive policy guidelines to contain the infection rate under a certain threshold.

In Senegal, Coxiella burnetii, which causes Q fever, has often been identified in ticks and humans near livestock, which are considered to be reservoirs and main sources of infection. We describe the emergence of C. burnetii in rodents, not previously known to carry this pathogen, and describe 2 new genotypes.

Understanding the transmission dynamics of infectious diseases is crucial for developing effective mitigation strategies. This study employs the airborne disease model combined with the SEIR epidemic model to analyze disease spread in enclosed environments while accounting for key epidemiological and environmental factors. The model incorporates parameters such as infection rate ( β ), incubation rate ( α ), recovery rate ( γ ), air exchange rates (ACH), quanta generation rate ( q ), room volume ( V ), and pulmonary ventilation rate ( p ), alongside varying population sizes ( N ). By simulating different scenarios over a 50‐day period, we assess the impact of initial infection conditions, recovery rates, and effective contact rates on epidemic progression. Our findings highlight the significant influence of ventilation and contact rates on disease spread, demonstrating that higher air exchange rates can mitigate transmission risks. The results provide critical insights into optimizing infection control strategies, particularly in indoor settings, by emphasizing the importance of air change rate, early interventions, and limiting contact rates.

OBJECTIVE: This study aimed to construct a job-exposure matrix (JEM) for the risk of being infected by infectious agents through airborne or droplet transmission in an occupational setting, which might lead to a respiratory disease. METHODS: An established COVID-19-JEM formed the basis for the development of the general airborne infectious agents JEM. Nine researchers in occupational epidemiology from three European countries (Denmark, The Netherlands and the United Kingdom) discussed and agreed on which factors from the COVID-19-JEM were relevant and whether new factors or adjustments of risk levels were needed. Adjustments to the COVID-19 JEM were made in a structured iterative. based on an expert assessment, a JEM on solar ultraviolet radiation (UVR) exposure including information on hours per day working inside, and national data on hours per week on site. Finally, a risk score was assigned to all factors for each job title within the International Standard Classification of Occupations system 2008 (ISCO-08). RESULTS: This airborne infectious agents JEM contains five factors: (i) hours spent per week on site, (ii) hours spent per day working inside, (iii) number and (iv) nature of contacts, and (v) being in close physical contact to others. Per occupation, a risk score ranging from 1 (low risk) to 3 (high risk) was provided for all five factors separately. CONCLUSION: This newly developed infectious agents JEM assesses the risk at population level using five factors. Following validation, this JEM could serve as a valuable tool in future studies investigating the role of work in the occurrence of a respiratory disease.

A new guideline for mitigating indoor airborne transmission of COVID-19 prescribes a limit on the time spent in a shared space with an infected individual (Bazant & Bush, Proceedings of the National Academy of Sciences of the United States of America , vol. 118, issue 17, 2021, e2018995118). Here, we rephrase this safety guideline in terms of occupancy time and mean exhaled carbon dioxide (${\\rm CO}_{2}$) concentration in an indoor space, thereby enabling the use of${\\rm CO}_{2}$monitors in the risk assessment of airborne transmission of respiratory diseases. While${\\rm CO}_{2}$concentration is related to airborne pathogen concentration (Rudnick & Milton, Indoor Air , vol. 13, issue 3, 2003, pp. 237–245), the guideline developed here accounts for the different physical processes affecting their evolution, such as enhanced pathogen production from vocal activity and pathogen removal via face-mask use, filtration, sedimentation and deactivation. Critically, transmission risk depends on the total infectious dose, so necessarily depends on both the pathogen concentration and exposure time. The transmission risk is also modulated by the fractions of susceptible, infected and immune people within a population, which evolve as the pandemic runs its course. A mathematical model is developed that enables a prediction of airborne transmission risk from real-time${\\rm CO}_{2}$measurements. Illustrative examples of implementing our guideline are presented using data from${\\rm CO}_{2}$monitoring in university classrooms and office spaces.

The global aging population, particularly those aged 60 and above, is increasingly vulnerable to communicable diseases. Building ventilation (BV) plays a key role in residential aged-care (RAC) facilities, where COVID-19 has had a significant impact. This study systematically reviews the published literature to examine the influence of BV systems (BVSs) on airborne disease (COVID-19) transmission in RACs and recommends strategies to protect vulnerable residents. Using the PRISMA framework, articles published in the last decade were sourced from Scopus, Web of Science, and PubMed. Bibliometric analyses revealed key research clusters on risk factors, transmission, facilities and services, and gender-based and retrospective studies. Australia, the USA, Africa, and the UK have made the most scholarly contributions to this field. Three main research areas emerged: BVS functionality, ventilation’s role in COVID-19 transmission, and spatial building design for effective airflow. Findings reveal that inadequate ventilation and poor indoor air quality are major contributors to disease spread, further influenced by ventilation rate, airflow, temperature, humidity, and air distribution. A hybrid ventilation design that integrates natural and mechanical systems with technologies such as HEPA filters, UVGI, and HVAC is recommended in the current study. In addition, building form and layout should incorporate spatial, engineering, administrative, and hierarchical controls in line with sustainable ventilation design guidelines. This study adds to the growing body of knowledge on the roles of ventilation and design in infection control. It offers practical recommendations for architects, RAC managers, government agencies, and policymakers involved in designing and managing RACs to reduce the risk of communicable disease transmission.

An operating room is a healthcare facility used to perform surgical operations on a patient. The OR demands high-air cleanliness and sterile conditions to reduce the risk of patients contracting surgical site infections. However, previous research stated that noticeable particle concentrations were identified near the surgery area. This scenario could elevate the tendency of particles to settle on the patient’s wound and subsequently cause SSIs. Therefore, this study examines the effectiveness of innovative localised exhaust and air curtains in reducing the number of particles settling on the patient. An OR model was constructed using computer-aided design (CAD), while the airflow and particle simulation were performed using computational fluid dynamics (CFD). The reliability of the present work was verified and validated using established data before the case study. A Re-Normalisation Group (RNG) k – ε model based on the Eulerian approach was used to simulate the airflow. In contrast, a discrete phase model (DPM) based on the Lagrangian approach was used to simulate the airborne particle dispersion. Results showed that the activation of the localised exhaust located on the two sides of the operating table could reduce the total particle settlement on the patient by 26% when compared to the baseline ventilation system. The installation of an additional air curtain showed the best performance in terms of reducing the particle settlement, followed by the installation of both an additional air curtain and a localised exhaust outlet. The particle concentration settled on a patient showed a positive relationship with the body surface area, which is expressed by equation y  = 0.1088 x  + 0.2528 with a coefficient of determination, R 2 value = 0.8764. This study suggests that adopting localised exhaust and air curtain systems in ORs could greatly improve infection control, enhance patient safety and elevate healthcare quality and outcomes.

Respiratory pathogens can be spread though the transmission of aerosolised expiratory secretions in the form of droplets or particulates. Understanding the fundamental aerosol parameters that govern how such pathogens survive whilst airborne is essential to understanding and developing methods of restricting their dissemination. Pathogen viability measurements made using Controlled Electrodynamic Levitation and Extraction of Bioaerosol onto Substrate (CELEBS) in tandem with a comparative kinetics electrodynamic balance (CKEDB) measurements allow for a direct comparison between viral viability and evaporation kinetics of the aerosol with a time resolution of seconds. Here, we report the airborne survival of mouse hepatitis virus (MHV) and determine a comparable loss of infectivity in the aerosol phase to our previous observations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Through the addition of clinically relevant concentrations of mucin to the bioaerosol, there is a transient mitigation of the loss of viral infectivity at 40% RH. Increased concentrations of mucin promoted heterogenous phase change during aerosol evaporation, characterised as the formation of inclusions within the host droplet. This research demonstrates the role of mucus in the aerosol phase and its influence on short-term airborne viral stability.

Advanced air treatment systems have the potential to reduce airborne infection risk, improve indoor air quality (IAQ) and reduce energy consumption, but few studies reported practical implementation and performance. PlasmaShield®, an advanced multi-modal HVAC-integrated system, was directly compared with a standard MERV-13 system in a post-surgical paediatric healthcare setting. The evaluation entailed monitoring of multi-size airborne particles, bioaerosols and key IAQ parameters. Measurements were taken for outside air, supply air and air in the occupied space for 3 days prior to, and after, the installation of the PlasmaShield system. Compared with the existing arrangement, very significant reductions in particle number concentrations were observed in the occupied space, especially with virus-like submicron particles. Significant reductions in airborne culturable bacteria and fungi were observed in the supply air, with more modest reductions in the occupied space. In the case of virus-like particles, there was an eight-fold improvement in equivalent clean air, suggesting a five-fold infection risk reduction for long-range exposure. The data suggest multiple benefits of airborne particle and bioaerosol reduction, with applications beyond healthcare. Long-term studies are recommended to confirm the combined IAQ, health and energy benefits.