Viral Load of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Respiratory Aerosols Emitted by Patients With Coronavirus Disease 2019 (COVID-19) While Breathing, Talking, and Singing

SARS-CoV-2 airborne transmission: a review of risk factors and possible preventative measures using air purifiers

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting worldwide death toll have prompted worries regarding its transmission mechanisms. Direct, indirect, and droplet modes are the basic mechanisms of transmission. SARS-CoV-2 spreads by respiratory droplets (size range >10 μm size ranges), aerosols (5 μm), airborne, and particulate matter. The rapid transmission of SARS-CoV-2 is due to the involvement of tiny indoor air particulate matter (PM_2.5), which functions as a vector. SARS-CoV-2 is more contagious in the indoor environment where particulate matter floats for a longer period and greater distances. Extended residence time in the environment raises the risk of SARS-CoV-2 entering the lower respiratory tract, which may cause serious infection and possibly death. To decrease viral transmission in the indoor environment, it is essential to catch and kill the SARS-CoV-2 virus and maintain virus-free air, which will significantly reduce viral exposure concerns. Therefore, effective air filters with anti-viral, anti-bacterial, and anti-air-pollutant characteristics are gaining popularity recently. It is essential to develop cost-effective materials based on nanoparticles and metal-organic frameworks in order to lower the risk of airborne transmission in developing countries. A diverse range of materials play an important role in the manufacturing of effective air filters. We have summarized in this review article the basic concepts of the transmission routes of SARS-CoV-2 virus and precautionary measures using air purifiers with efficient materials-based air filters for the indoor environment. The performance of air-filter materials, challenges and alternative approaches, and future perspectives are also presented. We believe that air purifiers fabricated with highly efficient materials can control various air pollutants and prevent upcoming pandemics.

Infectious droplet exposure is an inefficient route for SARS-CoV-2 infection in the ferret model

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) in humans, has a wide host range, naturally infecting felids, canids, cervids, rodents and mustelids. Transmission of SARS-CoV-2 is universally accepted to occur via contact with contaminated secretions from the respiratory epithelium, either directly or indirectly. Transmission via droplet nuclei, generated from a cough or sneeze, has also been reported in several human and experimental animal scenarios. However, the role of droplet transmission at the human-animal interface remains to be fully elucidated. Here, the ferret infection model was used to investigate the routes of infection for the SARS-CoV-2 beta variant (B.1.351). Ferrets were exposed to droplets containing infectious SARS-CoV-2, ranging between 4 and 106 µm in diameter, simulating larger droplets produced by a cough from an infected person. Following exposure, viral RNA was detected on the fur of ferrets, and was deposited onto environmental surfaces, as well as the fur of ferrets placed in direct contact; SARS-CoV-2 remained infectious on the fur for at least 48 h. Low levels of viral RNA were detected in the nasal washes early post-exposure, yet none of the directly exposed, or direct-contact ferrets, became robustly infected or seroconverted to SARS-CoV-2. In comparison, ferrets intranasally inoculated with the SARS-CoV-2 beta variant became robustly infected, shedding viral RNA and infectious virus from the nasal cavity, with transmission to 75 % of naive ferrets placed in direct contact. These data suggest that larger infectious droplet nuclei and contaminated fur play minor roles in SARS-CoV-2 transmission among mustelids and potentially other companion animals.

Viable SARS-CoV-2 Delta variant detected in aerosols in a residential setting with a self-isolating college student with COVID-19

The B.1.617.2 (Delta) variant of SARS-CoV-2 emerged in India in October of 2020 and spread widely to over 145 countries, comprising over 99% of genome sequence-confirmed virus in COVID-19 cases of the United States (US) by September 2021. The rise in COVID-19 cases due to the Delta variant coincided with a return to in-person school attendance, straining COVID-19 mitigation plans implemented by educational institutions. Some plans required sick students to self-isolate off-campus, resulting in an unintended consequence: exposure of co-inhabitants of dwellings used by the sick person during isolation. We assessed air and surface samples collected from the bedroom of a self-isolating university student with mild COVID-19 for the presence of SARS-CoV-2. That virus' RNA was detected by real-time reverse-transcription quantitative polymerase chain reaction (rRT-qPCR) in air samples from both an isolation bedroom and a distal, non-isolation room of the same dwelling. SARS-CoV-2 was detected and viable virus was isolated in cell cultures from aerosol samples as well as from the surface of a mobile phone. Genomic sequencing revealed that the virus was a Delta variant SARS-CoV-2 strain. Taken together, the results of this work confirm the presence of viable SARS-CoV-2 within a residential living space of a person with COVID-19 and show potential for transportation of virus-laden aerosols beyond a designated isolation suite to other areas of a single-family home.

Novel Dynamic Technique, Nano-DIHM, for Rapid Detection of Oil, Heavy Metals, and Biological Spills in Aquatic Systems

Numerous anthropogenic and natural particle contaminants exist in diverse aquatic systems, with widely unknown environmental fates. We coupled a flow tube with a digital in-line holographic microscopy (nano-DIHM) technique for aquatic matrices, for in situ real-time analysis of particle size, shape, and phase. Nano-DIHM enables 4D tracking of particles in water and their transformations in three-dimensional space. We demonstrate that nano-DIHM can be automated to detect and track oil spills/oil droplets in dynamic systems. We provide evidence that nano-DIHM can detect the MS2 bacteriophage as a representative biological-viral material and mercury-containing particles alongside other heavy metals as common toxic contaminants. Nano-DIHM shows the capability of observation of combined materials in water, characterizing the interactions of various particles in mixtures, and particles with different coatings in a suspension. The observed sizes of the particles and droplets ranged from ∼1 to 200 μm. We herein demonstrate the ability of nano-DIHM to characterize and distinguish particle-based contaminants in water and their interactions in both stationary and dynamic modes with a 62.5 millisecond time resolution. The fully automated software for dynamic and real-time detection of contaminants will be of global significance. A comparison is also made between nano-DIHM and established techniques such as S/TEM for their different capabilities. Nano-DIHM can provide a range of physicochemical information in stationary and dynamic modes, allowing life cycle analysis of diverse particle contaminants in different aquatic systems, and serve as an effective tool for rapid response for spills and remediation of natural waters.

Modeling the impact of indoor relative humidity on the infection risk of five respiratory airborne viruses

With a modified version of the Wells-Riley model, we simulated the size distribution and dynamics of five airborne viruses (measles, influenza, SARS-CoV-2, human rhinovirus, and adenovirus) emitted from a speaking person in a typical residential setting over a relative humidity (RH) range of 20-80% and air temperature of 20-25 °C. Besides the size transformation of virus-containing droplets due to evaporation, respiratory absorption, and then removal by gravitational settling, the modified model also considered the removal mechanism by ventilation. The trend and magnitude of RH impact depended on the respiratory virus. For rhinovirus and adenovirus humidifying the indoor air from 20/30 to 50% will be increasing the relative infection risk, however, this relative infection risk increase will be negligible for rhinovirus and weak for adenovirus. Humidification will have a potential benefit in decreasing the infection risk only for influenza when there is a large infection risk decrease for humidifying from 20 to 50%. Regardless of the dry solution composition, humidification will overall increase the infection risk via long-range airborne transmission of SARS-CoV-2. Compared to humidification at a constant ventilation rate, increasing the ventilation rate to moderate levels 0.5 → 2.0 h^-1 will have a more beneficial infection risk decrease for all viruses except for influenza. Increasing the ventilation rate from low values of 0.5 h^-1 to higher levels of 6 h^-1 will have a dominating effect on reducing the infection risk regardless of virus type.

SARS-CoV-2 Transmission and Prevention in the Era of the Delta Variant

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant transmits much more rapidly than prior SARS-CoV-2 viruses. The primary mode of transmission is via short range aerosols that are emitted from the respiratory tract of an index case. There is marked heterogeneity in the spread of this virus, with 10% to 20% of index cases contributing to 80% of secondary cases, while most index cases have no subsequent transmissions. Vaccination, ventilation, masking, eye protection, and rapid case identification with contact tracing and isolation can all decrease the transmission of this virus.

Comparing aerosol number and mass exhalation rates from children and adults during breathing, speaking and singing

Aerosol particles of respirable size are exhaled when individuals breathe, speak and sing and can transmit respiratory pathogens between infected and susceptible individuals. The COVID-19 pandemic has brought into focus the need to improve the quantification of the particle number and mass exhalation rates as one route to provide estimates of viral shedding and the potential risk of transmission of viruses. Most previous studies have reported the number and mass concentrations of aerosol particles in an exhaled plume. We provide a robust assessment of the absolute particle number and mass exhalation rates from measurements of minute ventilation using a non-invasive Vyntus Hans Rudolf mask kit with straps housing a rotating vane spirometer along with measurements of the exhaled particle number concentrations and size distributions. Specifically, we report comparisons of the number and mass exhalation rates for children (12–14 years old) and adults (19–72 years old) when breathing, speaking and singing, which indicate that child and adult cohorts generate similar amounts of aerosol when performing the same activity. Mass exhalation rates are typically 0.002–0.02 ng s −1 from breathing, 0.07–0.2 ng s −1 from speaking (at 70–80 dBA) and 0.1–0.7 ng s −1 from singing (at 70–80 dBA). The aerosol exhalation rate increases with increasing sound volume for both children and adults when both speaking and singing.

Severe acute respiratory syndrome coronavirus 2 can be detected in exhaled aerosol sampled during a few minutes of breathing or coughing

BACKGROUND

The knowledge on the concentration of viral particles in exhaled breath is limited. The aim of this study was to explore if severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be detected in aerosol from subjects with the coronavirus disease 2019 (COVID-19) during various types of breathing and coughing and how infection with SARS-CoV-2 may influence the number and size of exhaled aerosol particles.

METHODS

We counted and collected endogenous particles in exhaled breath in subjects with COVID-19 disease by two different impaction-based methods, during 20 normal breaths, 10 airway opening breaths, and three coughs, respectively. Breath samples were analyzed with reverse transcription real-time polymerase chain reaction (RT-PCR).

RESULTS

Detection of RNA in aerosol was possible in 10 out of 25 subjects. Presence of virus RNA in aerosol was mainly found in cough samples (n = 8), but also in airway opening breaths (n = 3) and in normal breaths (n = 4), with no overlap between the methods. No association between viral load in aerosol and number exhaled particles <5 μm was found. Subjects with COVID-19 exhaled less particles than healthy controls during normal breathing and airway opening breaths (all P < 0.05), but not during cough.

CONCLUSION

SARS-CoV-2 RNA can be detected in exhaled aerosol, sampled during a limited number of breathing and coughing procedures. Detection in aerosol seemed independent of viral load in the upper airway swab as well as of the exhaled number of particles. The infectious potential of the amount of virus detected in aerosol needs to be further explored.

International consensus on lung function testing during COVID-19 pandemic and beyond

COVID-19 has negatively affected the delivery of respiratory diagnostic services across the world due to the potential risk of disease transmission during lung function testing. Community prevalence, reoccurrence of COVID-19 surges, and the emergence of different variants of the SARS-CoV-2 virus have impeded attempts to restore services. Finding consensus on how to deliver safe lung function services for both patients attending and for staff performing the tests are of paramount importance.

This international statement presents the consensus opinion of 23 experts in the field of lung function and respiratory physiology balanced with evidence from the reviewed literature. It describes a robust roadmap for restoration and continuity of lung function testing services during the COVID-19 pandemic and beyond.

Important strategies presented in this consensus statement relate to the patient journey when attending for lung function tests. We discuss appointment preparation, operational and environmental issues, testing room requirements including mitigation strategies for transmission risk, requirement for improved ventilation, maintaining physical distance, and use of personal protection equipment. We also provide consensus opinion on precautions relating to specific tests, filters, management of special patient groups, and alternative options to testing in hospitals.

The pandemic has highlighted how vulnerable lung function services are and forces us to re-think how long term mitigation strategies can protect our services during this and any possible future pandemic. This statement aspires to address the safety concerns that exist and provide strategies to make lung function tests and the testing environment safer when tests are required.

[Infection prevention and control for COVID-19 in healthcare settings]

In healthcare facilities, the initial response to emerging and reemerging infectious diseases, including COVID-19, requires systematic management. The first step is to establish an initial risk assessment and subsequent response flow, using a combination of triage and clinical examination for patients. Screening tests are performed for the early diagnosis of asymptomatic patients who are judged to be at low risk in the initial assessment. However, regardless of the test results, subsequent patient care should be taken cautiously to avoid inadequate initial evaluation at the time of admission, follow-up of symptoms and infection control measures after admission. The basic principle is standard precautions, with particular emphasis on compliance with hand hygiene. Universal masking for preventing transmission from asymptomatic/pre-symptomatic patients and reducing droplet emission and inhalation become the new essential precaution. For suspected/confirmed patients with COVID-19, surgical mask or N95 mask, gloves, gown, eye protection, and cap are basically used. The policy for personal protective equipment is made based on the medical environment of each facility. A negative pressure room is not always required but should be considered in high-risk environments, if possible. While the risk of transmission from the surface environment in a standard healthcare delivery system is limited, a continuous review of the facility environment is expected, considering the importance of ventilation.