Visualization of the infection risk assessment of SARS-CoV-2 through aerosol and surface transmission in a negative-pressure ward

Lentinan Reduces Transmission Efficiency of COVID-19 by Changing Aerodynamic Characteristic of Exhaled SARS-CoV-2 Aerosols in Golden Hamsters

Lentinan (LNT) was found to reduce the aerosol transmission rate between golden hamsters from 100% (9/9) to 44.4% (4/9). The viral loads in the respiratory system, including the nasal turbinate, trachea, and lung, were significantly reduced in the infected golden hamsters that received LNT treatment. Furthermore, the amount of exhaled virus aerosols in hamsters treated with LNT was significantly lower than that in untreated hamsters throughout the entire disease progression. In detail, the amounts of virus-laden particles with aerodynamic diameters less than 5 µm exhibited a significant decreasing trend following LNT treatment. Moreover, the detection rate of infectious SARS-CoV-2 in each stage of the Anderson-6 sampler exhibited a decreasing trend following LNT treatment post-infection. In summary, our findings indicate that LNT therapy represents a promising therapeutic candidate for the treatment of COVID-19 patients. Meanwhile, during the course of treatment, LNT has the potential to reduce viral infectivity in affected individuals.

Severity and risk to inhalation of pathogen-laden aerosol in large public spaces: Insights from fangcang shelter hospitals under multi-location release

The key to strengthening the inherent safety of large public spaces and implementing precise preventive measures lies in clarifying the transmission risks of respiratory infectious diseases based on multiple factors. This work innovatively improves a pathogen inhalation infection risk prediction model and attempts to apply it to a Fangcang Shelter Hospital to investigate the effect of pathogen release location on risk distribution and the role of airflow distribution in risk control mechanisms. The model used in the study improved in resolution and accuracy, shedding light on the airflow distribution mechanisms involved in pathogen transport and risk control, thus providing a quantitatively realistic landscape of the spread of respiratory infectious diseases in large indoor environments. Predictions reveal a significant unevenness in the spatial distribution of infection probabilities within the multi-patient shelter unit, which is further exacerbated by different release locations, and that extreme infection risks can reach 4 to 14 times the average. Additionally, the study noted that the infection probability in the medical staff area due to the long-distance transmission of contaminants can reach as high as 1.72 % and that patients from ward 6# could potentially infect a healthcare worker every four days.

Air disinfection performance of upper-room ultraviolet germicidal irradiation (UR-UVGI) system in a multi-compartment dental clinic

Multi-compartment dental clinics present significant airborne cross-infection risks. Upper-room ultraviolet germicidal irradiation (UR-UVGI) system have shown promise in preventing airborne pathogens, but its available application data are insufficient in multi-compartment dental clinics. Therefore, the UR-UVGI system's performance in a multi-compartment dental clinic was comprehensively evaluated in this study. The accuracy of the turbulence and drift flux models was verified by experimental data from ultrasonic scaling. The effects of the ventilation rate, irradiation zone volume, and irradiation flux on UR-UVGI performance were analyzed using computational fluid dynamics coupled with a UV inactivation model. Different patient numbers were considered. The results showed that UR-UVGI significantly reduced virus concentrations and outperformed increased ventilation rates alone. At a ventilation rate of six air changes per hour (ACH), UR-UVGI with an irradiation zone volume of 20% and irradiation flux of 5 μW/cm2 achieved a 70.44% average virus reduction in the whole room (WR), outperforming the impact of doubling the ventilation rate from 6 to 12 ACH without UR-UVGI. The highest disinfection efficiency of UR-UVGI decreased for WRs with more patients. The compartment treating patients exhibited significantly lower disinfection efficiency than others. Moreover, optimal UR-UVGI performance occurs at lower ventilation rates, achieving over 80% virus disinfection in WR. Additionally, exceeding an irradiation zone volume of 20% or an irradiation flux of 5 μW/cm2 notably reduces the improvement rates of UR-UVGI performance. These findings provide a scientific reference for strategically applying UR-UVGI in multi-compartment dental clinics.

Fomite disinfection using spray systems: A computational multi-physics framework

Disinfecting inanimate objects or materials carrying infectious agents, i.e., fomites, using spray systems reduces healthcare-associated infections in medical settings and community-acquired infections in non-medical environments. However, an accurate prediction of such systems is challenging as these systems embrace multi-physics phenomena depending on several parameters. Therefore, this paper presents a computational modeling-based multi-physics framework to evaluate the performance and effectiveness of spray systems employed in disinfecting fomites with non-porous hydrophilic surfaces. The framework includes four key phases: (i) atomizing the liquid disinfectant jet into the disinfectant droplets; (ii) interactions between disinfectant droplets and the surrounding air; (iii) impingements created by the disinfectant droplets on the fomite surface; (iv) interactions between the disinfectant depositions and pathogens causing fomite disinfection. The accuracy of the framework is evaluated using two sets of experimental data on the reduction of viable Bacillus atrophaeus spores over an 1800-second period. The results show that the framework can predict fomite disinfection via spray systems, with the deviations from the measured data being 2.73% and 2.38%. By presenting a detailed perception of the dynamics involved in fomite disinfection, this framework has the potential to improve public health practices and lead to the development of more effective and targeted disinfection strategies in diverse settings.

Susceptibility and exposure risk to airborne aerosols in intra-urban microclimate: Evidence from subway system of mega-cities

The health of intra-urban population in modern megacities relies largely on the biosafety within the microclimate of subway system, which can be vulnerable to epidemical challenges brought by virus-laden bioaerosols under varying factors. The literature has yet to address the association between the exposure risks to infectious pathogens and the dynamic changes of boundary conditions in this densely populated microclimate. This study aims at characterizing the bioaerosol dispersion, evaluating the exposure risks under various train arrival scenarios and hazard releasing positions in a real-world double-decker subway station. The results provide the evidence for the dominating airflow pattern, bioaerosols dispersion behaviors, exposure risk, and evacuation guidance in a representative microclimate of mega-cities. The tunnel effects of nearby pedestrian passageways are found to be dominating the airflow pattern, leading to the discharging of airborne bioaerosols. At least 60 % increasing of discharging rate of bioaerosol is attributed to the arrival of one or two trains at the subway platform compared with the scenario with no train arriving. Results from risk assessment with improved Wells-Riley model estimate 57.62 % of maximum infectivity probability with no train arriving. Large areas near the source at the platform floor still cannot be considered safe within 20 min. For the other two scenarios where trains arrive at the platform, the maximum probability of infection is below 5 %. Moreover, the majority of train carriages can be regarded as safe zones, as the ventilation across the screen door are mostly directed towards the platform. Additionally, releasing the bioaerosols at the platform floor poses the most severe threats to human health, and the corresponding evacuation strategies are suggested. These findings offer practical guidance for the design of the intra-urban microclimate, reinforcing the need for exposure reduction device or contingency plans, and providing potential evacuation strategy towards improved health outcomes.

A review on sterilization methods of environmental decontamination to prevent the coronavirus SARS-CoV-2 (COVID-19 virus): A new challenge towards eco-friendly solutions

In recent years, the COVID-19 pandemic is currently wreaking havoc on the planet. SARS-CoV-2, the Severe Acute Respiratory Syndrome Coronavirus, is the current term for this outbreak. Reports about this novel coronavirus have been presented since the pandemic's breakout, and they have demonstrated that it transmits rapidly from person to person, primarily by droplets in the air. Findings have illustrated that SARS-CoV-2 can survive on surfaces from hours to days. Therefore, it is essential to find practical solutions to reduce the virus's impact on human health and the environment. This work evaluated common sterilization methods that can decontaminate the environment and items. The goal is that healthcare facilities, disease prevention organizations, and local communities can overcome the new challenge of finding eco-friendly solutions. Further, a foundation of information encompassing various sterilization procedures and highlighting their limits to choose the most appropriate method to stop disease-causing viruses in the new context has been presented. The findings of this crucial investigation contribute to gaining insight into the comprehensive sterilization approaches against the coronavirus for human health protection and sustainable environmental development.

Chargeability study of disinfectants and the optimization of design parameters of a handheld electrostatic disinfection device for small scale applications

Apart from aerosols, contaminated surfaces with SARS-CoV-2 virus are the significant carriers of virus transmission. The disinfection and sanitization of the indoor and outdoor places are one among the powerful and effective strategies to avoid the surface-to-human transmission of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) through frequent touch and physical contact. Electrostatic spraying is one of the effective and efficient methods to apply the liquid-based sprays on surfaces to be disinfected or sanitized. This technique covers the directly exposed and obscured surfaces uniformly and reaches to hidden areas of the target. In this paper, the design and performance parameters of a motorized pressure-nozzle based handheld electrostatic disinfection device were optimized and the chargeability of ethanol (C2H5OH), formaldehyde (CH2O), glutaraldehyde (C5H8O2), hydrogen peroxide (H2O2), phenol (C6H5OH) and sodium hypochlorite (NaClO) has been critically investigated. The chargeability indicator for disinfectants was presented in terms of the charge-to-mass ratio. The significant value of the charge-to-mass ratio of 1.82 mC/kg was achieved at an applied voltage of 2.0 kV, the liquid flow rate and pressure of 28 ml/min and 5 MPa, respectively. The experimental results are well aligned to the proposed theoretical context.

Adsorption of the First-Line Covid Treatment Analgesic onto Activated Carbon from Residual Pods of Erythrina Speciosa

In this study, the residual pods of the forest species Erythrina speciosa were carbonized with ZnCl₂ to obtain porous activated carbon and investigated for the adsorptive removal of the drug paracetamol (PCM) from water. The PCM adsorption onto activated carbon is favored at acidic solution pH. The isothermal studies confirmed that increasing the temperature from 298 to 328 K decreased the adsorption capacity from 65 mg g^-1 to 50.4 mg g^-1 (C₀ = 175 mg L^-1). The Freundlich model showed a better fit of the equilibrium isotherms. Thermodynamic studies confirmed the exothermic nature (ΔH⁰ = -39.1066 kJ mol^-1). Kinetic data indicates that the external mass transfer occurs in the first minutes followed by the surface diffusion, considering that the linear driving force model described the experimental data. The application of the material in the treatment of a simulated effluent with natural conditions was promising, presenting a removal of 76.45%. Therefore, it can be concluded that the application of residual pods of the forest species Erythrina speciosa carbonized with ZnCl₂ is highly efficient in the removal of the drug paracetamol and also in mixtures containing other pharmaceutical substances.

Environmental Dissemination of SARS-CoV-2 in a University Hospital during the COVID-19 5th Wave Delta Variant Peak in Castile-León, Spain

The dominant SARS-CoV-2 Delta variant (B.1.617.2) became the main circulating variant among countries by mid 2021. Attention was raised to the increased risk of airborne transmission, leading to nosocomial outbreaks even among vaccinated individuals. Considering the increased number of COVID-19 hospital admissions fueled by the spread of the variant, with Spain showing the highest COVID-19 rates in mainland Europe by July 2021, the aim of this study was to assess SARS-CoV-2 environmental contamination in different areas of a University Hospital in the region of Castile-León, Spain, during the peak of the 5th wave of COVID-19 in the country (July 2021). Air samples were collected from sixteen different areas of the Hospital using a Coriolis® μ air sampler. Surface samples were collected in these same areas using sterile flocked plastic swabs. RNA extraction followed by a one-step RT-qPCR were performed for detection of SARS-CoV-2 RNA. Of the 21 air samples, only one was positive for SARS-CoV-2 RNA, from the emergency waiting room. Of the 40 surface samples, 2 were positive for SARS-CoV-2 RNA, both from the microbiology laboratory. These results may be relevant for risk assessment of nosocomial infection within healthcare facilities, thus helping prevent and minimize healthcare staff's exposure to SARS-CoV-2, reinforcing the importance of always wearing appropriate and well-fit masks at all times and proper PPE when in contact with infected patients.

Parapoxvirus-based therapy eliminates SARS-CoV-2-loaded fine aerosol and blocks viral transmission in hamster models

Currently, it is believed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an airborne virus, and virus-containing aerosol particles have been found concurrent with the onset of COVID-19, which may contribute to the noncontact transmission of SARS-CoV-2. Exploring agents to block SARS-CoV-2 transmission is of great importance to prevent the COVID-19 pandemic. In this study, we found that inactivated Parapoxvirus ovis (iORFV), a kind of immunomodulator, could compress the proportion of small particle aerosols exhaled by Syrian golden hamsters. Notably, the concentration of SARS-CoV-2 RNA-containing aerosol particles was significantly reduced by iORFV in the early stages after viral inoculation. Importantly, smaller aerosol particles (<4.7 μm) that carry infectious viruses were completely cleared by iORFV. Consistently, iORFV treatment completely blocked viral noncontact (aerosol) transmission. In summary, iORFV may become a repurposed agent for the prevention and control of COVID-19 by affecting viral aerosol exhalation and subsequent viral transmission.

Similar aerosol emission rates and viral loads in upper respiratory tracts for COVID-19 patients with Delta and Omicron variant infection

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Aerosol emission rates of Delta or Omicron patients were similar.

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Viral loads in upper respiratory tract of Alpha, Delta and Omicron patients were similar.

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Viral loads in upper respiratory tract of vaccinated or unvaccinated Delta patients had no difference.