Aerosolized Transmission

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Aerosolized Transmission

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Decreasing humidity in the winter is likely to lead to more COVID-19 cases

11/8/20


https://www.news-medical.net/news/20201 ... cases.aspx


The coronavirus disease 2019 (COVID-19) pandemic continues to ravage across the globe a month before the winter season kickstarts. Health experts fear that the cold climate may cause skyrocketing cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the causative pathogen of COVID-19.

A team of researchers from the Center for Disease Dynamics, Economics & Policy, USA, and Johns Hopkins University, USA, found evidence to support the notion that increased humidity may have contributed to lesser cases in spring earlier this year (2020). However, as the winter season fast approaches, the researchers fear that the decreasing humidity is likely to lead to an increase in COVID-19 cases.

The study


So far, the coronavirus pandemic has infected over 50 million people worldwide and claimed the lives of at least 1.25 million. In the United States, there are over 9.95 million cases and at least 237,000 deaths.

The primary mode of transmission of SARS-CoV-2 is through respiratory droplets from infected people. Recent evidence has suggested that the virus can also spread through airborne particles.

The first wave of cases in the United States came in the late winter of 2019-2020, but overall most of the cases occurred during the spring and summer. As the fall season begins in the Northern Hemisphere, the weather will become drier and colder.

Past studies have shown that falling humidity is tied to increased transmission rates of other respiratory diseases, such as influenza. Experts believe that the same is true in COVID-19, and the nearing winter may lead to a surge of new cases as the present spike in infections across the Northern Hemisphere has already been suggested.

The current study, which appeared on the pre-print server medRxiv* in November 2020, highlights the role of humidity and climate in the spread of SARS-CoV-2. To arrive at the study findings, they used dynamic time warping to cluster all 3,137 counties in the United States based on temporal data on absolute humidity between March and September.

From there, they utilized a multivariate generalized additive model that combined data on human mobility obtained from mobile phone data with humidity data. This way, they could determine the possible effect of absolute humidity and mobility on new daily cases of SARS-CoV-2 infection.

Study findings

The team found ten groups of counties with similar humidity levels in the United States. They also found a significant negative effect between increased humidity levels and new cases of COVID-19 in most regions, especially between March and July.

The effect was more significant in regions with lower humidity, such as the Midwest, Western and Northeast regions of the United States.

In the two regions that incurred the largest effect, a 1 g/m3 increase in absolute humidity has resulted in a 0.21 and 0.15 decrease in cases.

The increasing humidity seems to have played a role in the decreasing cases in the spring. They conclude, then, that increasing humidity is linked to an increase in COVID-19 cases.


“Furthermore, the fact that mobility data were positively correlated suggests that efforts to counteract the rise in cases due to falling humidity can be effective in limiting the burden of the pandemic,” the team added.

Approaching winter

The looming winter in the United States and other countries raises concerns about the COVID-19 pandemic’s prognosis over the coming months. Other respiratory illnesses, such as those caused by influenza, middle east respiratory syndrome coronavirus (MERS-CoV), and the severe acute respiratory syndrome coronavirus (SARS-CoV-1), increase in number during the cold season.

The researchers said that as the absolute humidity decreases during the winter season, COVID-19 cases may increase over the next couple of months. If this happens, health care systems across the globe will experience a further strain, which may lead to the lack of hospital beds for the severely ill patients infected with the virus.

“Increasing COVID-19 cases will pose an issue for many healthcare systems, which in normal years are typically stretched thin from regular seasonal infections, such as influenza,” the team wrote in the paper.

“Furthermore, seasonal changes in human behavior may also impact the number of new cases and hospitalizations since people are more likely to occupy indoor spaces for longer durations when outdoor temperatures decrease, thus increasing the risk of transmission,” they added.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information

Source:

COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU), https://gisanddata.maps.arcgis.com/apps ... 7b48e9ecf6

Journal reference:


Lin, G., Hamilton, A., Gatalo, O, et al. (2020). Investigating the effects of absolute humidity and human encounters on transmission of COVID-19 in the United States. medRxiv. doi: https://doi.org/10.1101/2020.10.30.20223446, https://www.medrxiv.org/content/10.1101 ... 20223446v1
trader32176
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Aerosolized Transmission

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Cooler temperatures in U.S. may increase COVID-19 cases: New modeling study

11/9/20


https://www.news-medical.net/news/20201 ... study.aspx


How temperature affects the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a question asked since the pandemic's early days. Just like the flu, which has a substantial seasonal variation, it is believed that SARS-CoV-2 also may be affected by temperature.

Some modeling studies indicate that cases will increase as the weather cools. Early studies using data from different countries looked at how fast the number of cases increased and suggested temperatures of 0–10 ºC were the most favorable for spread.

Models that incorporate weather data like humidity, temperature, pollution, and others do not generally have the statistical power to define how they affect the response accurately. Hence, when other inputs like demographics and time trends are added, their effect is lost. In addition, during the early stages of the pandemic, the quality of statistical data available may not have been very reliable.

Although current data reporting has become stable, there is still a difference between actual COVID-19 cases or deaths and when they are reported. Further adding the weather variables that could have influenced the event could add to the already present biological variations.

Modeling temperature response of COVID-19 cases

In a new modeling study published as a preprint paper on the medRxiv* server, a diverse team of researchers reports how SARS-CoV-2 transmission in the U.S. changes with temperature. The authors gathered about 2500 observations from April 16-July 15, 2020, on state-level deaths, positive cases, and tests. They obtained temperature data from the U. S. National Weather Service.

The researchers from the University of California, San Diego, software company Laserfiche, James Hardie Building Products, and Wake Forest University obtained weather data from airports with the most commercial traffic in each state. Because of this, measurement errors are small, write the authors, with about 60% of the U.S. population living within 300 km from the representative airport in their state.

Upon analyzing the data, they found that daily deaths fell from April to the end of May, and then became almost flat. At the same time, the temperatures were rising. As the temperature decreases to 10–5 ºC, there is an almost exponential increase in the number of positive cases.

Next, they simulated different scenarios for daily deaths from COVID-19 by changing the different variables they used in their model. Taking the data from Georgia as an example and changing the temperature from 31 ºC to 5 ºC, they found that daily deaths increased with decreasing temperatures.

It has been suggested that states like Hawaii that are geographically isolated and have small populations might have reduced COVID-19 deaths with warmer weather. However, the authors suggest this is unlikely, given previous reports that have suggested that increasing temperatures by itself is not enough to stop the spread of the virus.

The team also modeled the number of new positive cases as a function of temperature normalized to a value at 31 ºC. This is a temperature close to the summer maximums in the U.S. The model predicts that the number of new positive cases increases as the temperature decreases by almost 400% as temperature drops from 31 ºC to 5 ºC.

Cases projected to increase in winter

The model shows that the relationship between new positive cases and temperatures is more pronounced than the relationship between the deaths and temperature. Thus, although summer temperatures may be helping reduce virus transmission, transmission still needs to be brought under control.

Reducing temperatures with the advent of fall and winter will dramatically increase the number of positive cases and deaths, predicts the model.

Apart from a static model, the authors also developed a dynamic model where the temperature affected the daily deaths, and which is then used for further projections. Apart from the direct effect of temperature on the death counts, there is also an indirect effect, compounding the effect of temperature-driven daily deaths when the initial death counts lag this output in the simulation.

This dynamic model suggests a delay in responding to increasing positive cases with cooler temperatures will rapidly increase in cases. "This is already being seen in the current spatial pattern of outbreaks," write the authors.

Furthermore, according to the authors, summer's warmer temperatures may have helped reduce the number of cases and contributed to a false sense of the effect of the efforts. The winter will present more challenges with colder temperatures. Along with the fear of increasing flu during the winter months, COVID-19 transmission will also increase during these months.

The authors write, "Investment in providing the pandemic modeling community with timely counts based on death certificate dates would allow them to deliver substantially more accurate and timely warnings of impending upturns."
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Re: Aerosolized Transmission

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How weather affects SARS-CoV-2 transmission: A US-based case study

11/18/20


https://www.news-medical.net/news/20201 ... study.aspx


How changes in the weather affect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its transmissibility has been the topic of several studies. The preoccupation of researchers with this aspect of the coronavirus disease 2019 (COVID-19) pandemic follows from observations that the flu virus and other coronaviruses follow seasonal patterns. Understanding how SARS-CoV-2’s transmissibility is affected by seasonal changes can thus help us to develop more informed preventative measures against its spread.

Laboratory studies have shown that SARS-CoV-2 – the causative pathogen of COVID-19 – is not very stable in warmer temperatures and high humidity. Other studies have found both positive and negative associations between the weather and viral transmission, based on daily confirmed case statistics.

However, using daily positive cases may not be very useful in studying the climate’s effect of SARS-CoV-2’s transmission. For instance, this data does not include the many cases that go undocumented, the lag between infection and symptom onset and the lag between testing and reporting. Additionally, many studies have not controlled for other confounding factors such as the implementation of health interventions, socioeconomic factors and other environmental factors.

To account for these issues, the authors used the mean reproduction number to allow for delayed reports, unreported infections and population movements. The authors also controlled for other factors like smoking, air pollution, and obesity and making the model stronger.

Researchers from Yale University and Columbia University in the United States have published a paper on the medRxiv* preprint server that explores further the relationship between SAR-CoV-2 transmissibility and the weather. The team looked at the association between air temperature and humidity on SARS-CoV-2 transmission in the US based on the virus’s reproduction number, a metric used to calculate the rate of infection of a pathogen in a population. They define the reproduction number as the mean number of new infections caused by a single infected individual, taking into account public health interventions and assuming everyone in the population is susceptible.

Modeling virus transmission and weather

The team gathered temperature and specific humidity data for 913 US counties, specific humidity being defined as the mass of water vapor in a unit mass of moist air. They also collected other data for the counties, such as geographic location, population demographics, socioeconomic factors and air pollution.

They estimated the daily reproduction number using a metapopulation model where they considered two types of movements: daily commuting for work and random movement. They fitted the transmission model to county-level deaths and daily cases reported between 15 March 2020 and 31 August 2020.

They found the mean reproduction number to be between 0.46 and 5.43. The daily mean temperature varied widely between about 14 and 40 ºC, and the specific humidity varied between about 1 and 22 g/kg.

The largest number of cumulative cases per 100,000 people was in Chattahoochee County, Georgia; conversely, Taylor County, Florida, had the lowest number. Counties in the south were generally hotter and more humid than northern US counties, and coastal counties were cooler and more humid than counties inland.

Using this model, the researchers found lower temperatures were associated with higher transmission of SARS-CoV-2, below an optimum temperature of 32.6 ºC. There was no association above the optimum temperature, however.

The relationship between the reproduction number and specific humidity was non-linear. There was lower transmission at higher specific humidity, except for an increase between 9 to 15 g/kg.

The authors also estimated the fraction of the reproduction number attributable to temperature or specific humidity. Across the 913 counties studied, the fraction attributed to temperature was 5.1%, and the fraction attributed to humidity was 14.5%. The attributable fraction for temperature increased from south to north. The attributable fraction for humidity increased from south to north in eastern parts of the country, while in the western parts, the attributable fraction was lower in coastal counties and higher inland.

Humidity affects transmission more than temperature

The authors found lower temperatures and lower specific humidity were associated with an increased reproduction number, or higher viral transmission. SARS-CoV-2 transmission was associated more with temperature and humidity in colder and drier counties than in warmer and more humid counties. These results are thus in line with some previous studies in the area.

Lab testing of SARS-CoV-2’s acclimation to temperature and humidity alterations also found it to be less stable at higher temperatures and humidity compared to lower temperatures and humidity. Furthermore, the SARS-CoV-2 virus half-life decreased when relative humidity was increased from 40% to 65% at 22 ºC and 27 ºC, but increased when the humidity increased from 65% to 85%. This is similar to the non-linear association found using the present study’s model.

Thus, the specific humidity contributed more to virus transmission than temperature, but it was not clear if humidity is a cause or an indicator of virus transmission. Further study in this area will need to be done to clarify this issue.
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Re: Aerosolized Transmission

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Scientists studying aerodynamics of infectious disease reveal ways to reduce indoor SARS-CoV-2 transmission

11/23/20


https://www.news-medical.net/news/20201 ... ssion.aspx


The coronavirus disease, caused by the agent severe acute respiratory syndrome 2 (SARS-CoV-2) wreaks havoc across the globe, with its second wave occurring in many countries.

With the winter season fast approaching in the northern hemisphere, more people will stay indoors, which could lead to greater virus spread. Past studies have shown that indoor spread of the virus, especially in offices, grocery stores, concert halls, and other places with less ventilation, may ramp up as the cold season kicks in.

At the 73rd Annual Meeting of the American Physical Society's Division of the Americal Physical Society's Division of Fluid Dynamics, researchers presented a range of studies investigating the aerodynamics of infectious disease.

One study results revealed that the number of micron-scale expiratory particles emitted during vocalization, such as singing or speaking, dramatically increases with loudness. The number of virus particles is also increased markedly by coughing.

How COVID-19 spreads

The SARS-CoV-2 primarily spreads through contact and respiratory droplets. Under some circumstances, the airborne transmission may happen, such as when aerosol-generating procedures are performed in healthcare settings, when in crowded indoor environments with poor ventilation, and when people speak, breathe, or sing.

The U.S. Centers for Disease Control and Prevention (CDC) updated its guidelines, acknowledging that SARS-CoV-2 spreads through aerosols. The World Health Organization (WHO) also recognized the coronavirus's potential to spread via aerosols, hence, recommends people to avoid closed areas with poor ventilation.

With the potential of airborne transmission, the health agencies reiterate the importance of basic infection protocols to prevent infection, such as wearing masks, physical distancing, and regular hand hygiene.

Virus spread by singing and speaking

Past research has shown the role played by large, fast-falling objects produced by coughing or sneezing. In some superspreader events, people got infected with SARS-CoV-2 when they were with other people indoors. For instance, of the 61 singers in Washington state, 53 contracted the virus after a 2.5-hour choir rehearsal in March. In another incident, 24 of the 67 passengers who were on board a bus for two hours got infected with the virus in Zhejiang Province in China.

In one report, William Ristenpart, a chemical engineer at UC Davis, revealed that when people speak or sing loudly, they generate more micron-sized particles compared to when they use a normal voice.

"Theoretical calculations suggest that vocalizing less often and more quietly yields substantial decreases in transmission probability," the report explained. Further, the report added that the particles produced when shouting or yelling greatly surpass the number produced during coughing.

In experiments in guinea pigs, study researchers emphasized that influenza is transmitted via aerosolized fomites, which are virus-contaminated dust particles released from animals' fur and cages, not from their expiration. The team concluded that these fomites could be released from sources regularly used by people, including tissue papers.

"Our results suggest that researchers should expand their focus beyond coughing and sneezing as the presumed mechanism for airborne disease transmission," the study authors concluded.

Spread via musical instruments

Another study by researchers from the University of Colorado, Boulder, focused on how the virus might spread through musical instruments. The team conducted experiments to measure aerosol emissions from musical instruments.

The team said that flutes, for instance, do not generate that many aerosols when used. However, instruments such as oboes and clarinets, which have wet and vibrating surfaces, tend to produce many aerosols.

Aerosol emissions from musical instruments can be controlled. When a mask is placed over a trumpet or clarinet bell, it reduces the number of airborne particles back down to levels in a normal tone of voice.

Meanwhile, a research team at the University of Minnesota revealed that though the amount of aerosols produced differ by musician and instrument, they rarely traveled more than a foot away. Hence, the team designed a pandemic-sensitive seating model for live orchestras. They also decided where to place filters and audience members to reduce the risk of virus spread.


In the workplace

During the pandemic, many employees opted to work from home. As restrictions are eased, employers are exploring ways to safely reopen their workplaces by sustaining physical distance among their employees. A team of researchers at Carnegie Mellon University used two-dimensional simulations that modeled people as particles. They identified specific conditions that would help avoid crowding in confined spaces such as hallways.

One of the problems employees face amid the global health crisis is commuting to and from office buildings. Since passenger cars also pose an infection risk, a team of researchers at Brown University computed how air moves through passenger car cabins to determine strategies to reduce the risk of virus spread. For instance, opening some windows strategically while closing others can help reduce the risk.

As the new normal starts to set in among many countries identifying ways to reduce virus spread is crucial to combat the COVID-19 pandemic.
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COVID-19 study underscores the importance of protection guidelines based on fluid dynamics research

11/24/20


https://www.news-medical.net/news/20201 ... earch.aspx


Researchers who study the physics of fluids are learning why certain situations increase the risk that droplets will transmit diseases like COVID-19.

At the 73rd Annual Meeting of the American Physical Society's Division of Fluid Dynamics, the scientists offered new evidence showing why it's dangerous to meet indoors--especially if it's cold and humid, and even if you're more than six feet away from other people.

They suggested which masks will catch the most infectious droplets. And they provided new tools for measuring super-spreaders.

" Present epidemiological models for infectious respiratory diseases do not account for the underlying flow physics of disease transmission."

- Swetaprovo Chaudhuri, Professor, University of Toronto Engineering

But fluids and their dynamics are critical for shaping pathogen transport, which affects infectious disease transmission, explained mathematical physicist and professor Lydia Bourouiba, Director of The Fluid Dynamics of Disease Transmission Laboratory at MIT.

She gave an invited talk on the body of work she has produced over the last ten years elucidating the fluid dynamics of infectious diseases and disease transmission.

"My work has shown that exhalations are not isolated droplets but in fact come out as a turbulent, multiphase cloud. This gas cloud is critical in enhancing the range and changing the evaporation physics of the droplets within it," said Bourouiba.

"In the context of respiratory infectious diseases, particularly now COVID-19, this work underscores the importance of changing distancing and protection guidelines based on fluid dynamics research, particularly regarding the presence of this cloud."

Bourouiba presented examples from a range of infectious diseases including COVID-19 and discussed the discovery that exhalation involves different flow regimes, in addition to rich unsteady fluid fragmentation of complex mucosalivary fluid.

Her research reveals the importance of the gas phase, which can completely change the physical picture of exhalation and droplets.

Nordic Institute for Theoretical Physics scientist Dhrubaditya Mitra and his team realized they could use the mathematical equations that govern perfume to calculate how long it would take for viral droplets to reach you indoors. It turns out: not very long at all.

Perfume worn by someone at the next table or cubicle reaches your nose thanks to turbulence in the air. Fine droplets spewed by an infected person spread in the same way. The researchers found that below a relative distance known as the integral scale, droplets move ballistically and very fast.

Even above the integral scale, there is danger. Consider an example where the integral scale is two meters. If you were standing three meters--just under ten feet--from an infected person, their droplets would almost certainly reach you in about a minute.

"It showed us how futile most social distancing rules are once we are indoors," said Mitra, who conducted the research with colleague Akshay Bhatnagar at the Nordic Institute for Theoretical Physics and Akhilesh Kumar Verma and Rahul Pandit at the Indian Institute of Science.

Besides traveling further and faster, droplets may also survive longer indoors than previously believed.

Research in the 1930s analyzed how long respiratory droplets survive before evaporating or hitting the ground. The nearly century-old findings form the basis of our current mantra to "stay six feet away" from others.

Physicists from the University of Twente revisited the issue. They conducted a numerical simulation indicating that droplet lifetimes can extend more than 100 times longer than 1930s standards would suggest.

"Current social distancing rules are based on a model which by now should be outdated," said physicist Detlef Lohse, who led the team.

In a cold and humid space, exhaled droplets don't evaporate as quickly. The hot moist puff produced also protects droplets and extends their lifetimes, as do collective effects.

Some droplets are more likely than others to make you sick. University of Toronto's Chaudhuri, with researchers from the Indian Institute of Science and the University of California San Diego, investigated why, using human saliva droplet experiments and computational analyses.

They found that some of the most infectious droplets start out at 10 to 50 microns in size. "With certain assumptions, it appears that if everyone wears a mask that can prevent ejection of all droplets above 5 microns, the pandemic curve could be flattened," said Chaudhuri.

Dried droplet residue also poses a serious risk: It persists much longer than droplets themselves and can infect large numbers of people if the virus remains potent.

The team used their findings to develop a disease transmission model. "Our work connects the microscale droplet physics and its fundamental role in determining the infection spread at a macroscale," said Chaudhuri.

To better understand droplet dynamics in the COVID-19 pandemic, a team from Northwestern University and the University of Illinois at Urbana-Champaign tested the capacities of a new wearable device.

The thin, wireless, flexible sensor attaches like a sticker to the bottom of the neck to capture vital signals. Ongoing clinical studies are using the device with hospital patients.

The team found that the device distinguishes between coughing, talking, laughing, and other breathing activities with its machine learning algorithms. Researchers used particle tracking velocimetry and a decibel meter to analyze droplets produced by device wearers.

"Different types of speech can generate drastically different numbers and dynamics of droplets," said biomedical engineering researcher Jin-Tae Kim, who led the investigation.

The device can help shed light on why some individuals become unusually infectious--the so-called super-spreaders. "Our findings further address the critical need for continuous skin-integrated sensors to better comprehend the pandemic," said Kim.
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Research provides key information on transmission, development of mutations in SARS-CoV-2 virus

11/24/20


https://www.news-medical.net/news/20201 ... virus.aspx


In the COVID-19 pandemic, 57 million people have already been infected worldwide. In the search for vaccines and therapies, a precise understanding of the virus, its mutations, and transmission mechanisms are crucial.

A recent study by the research group of Principal Investigator Andreas Bergthaler at the CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, in the renowned journal Science Translational Medicine, makes an important contribution to this.

The high quality of epidemiological data in Austria, together with state-of-the-art virus genome sequencing, has supported unprecedented insights into the mutation behavior and transmission of the SARS-CoV-2 virus.

The project "Mutational dynamics of SARS-CoV-2 in Austria" was launched by CeMM in close cooperation with the Medical University of Vienna at the end of March. Together with the Austrian Agency for Health and Food Safety (AGES) and in cooperation with numerous universities and hospitals all over Austria, scientists are working on drawing a more precise picture of the virus mutations and transmissions that occur by genome sequencing of SARS-CoV-2 viruses.

Under the leadership of CeMM Principal Investigators Andreas Bergthaler and Christoph Bock, 750 samples from important SARS-CoV-2 infection clusters in Austria such as the tourist town of Ischgl and Vienna were phylogenetically and epidemiologically reconstructed and their role in transcontinental virus spread was analyzed.

The results also provide important information on transmission and the development of mutations in the SARS-CoV-2 virus.

Mutation analyzes revealed correlations between clusters

Based on epidemiological data, the scientists used mutation analyses to reconstruct a SARS-CoV-2 cluster consisting of 76 cases and to uncover a cryptic link between two epidemiological clusters.

"This example illustrates how contact tracing and virus mutation analysis together provide a strong pillar of modern pandemic control," says project leader Andreas Bergthaler. Franz Allerberger, Head of the Public Health Division of AGES and co-author of the study, agrees: "The modern techniques of virus genome sequencing support epidemiological contact tracing and offer high-resolution insights of the ongoing pandemic."

Researchers observe the development of new mutations


A special feature of the study is that a chain of eight consecutive transmissions was analyzed. "The transmission chain started with a returnee from Italy. Within 24 days, the SARS-CoV-2 virus spread in the greater Vienna region via public and social events in closed rooms", say the CeMM study authors Alexandra Popa and Jakob-Wendelin Ginger.

The precise breakdown of the transmission chain enabled scientists to closely observe the development of a new mutation of SARS-CoV-2.

"Thanks to excellent epidemiological and our deep virus sequencing data, we could follow how the SARS-CoV-2 virus mutated in one individual and was then transmitted to others," explains Andreas Bergthaler. In addition, the scientists observed the mutation behavior of the virus during the course of the disease in 31 patients.

This may help in the future to assess whether treatments influence the mutation characteristics of the virus.

On average 1,000 virus particles are transmitted during an infection

The results of the current analyses also show that on average 1000 infectious virus particles are transmitted from one infected person to the next.

These values are overall considerably higher than for other viruses such as HIV or noroviruses. Andreas Bergthaler adds:


" Yet, occasionally we also found infected people who apparently came into contact with fewer virus particles and still became infected. We suspect that parameters such as the application of protective measures, the transmission route or the immune system may play a decisive role here."

- Andreas Bergthaler, Proncipal Investigator, CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences

These results raise important new questions and hypotheses. Reducing the viral load of infected individuals by a combination of measures such as mouth-nose protection, physical distance and adequate indoor air exchange could play a key role in both preventing the spread of the virus and possibly even influence the course of the disease.

The current study based on data collected during the early phase of the SARS-CoV-2 pandemic in spring 2020, provides important insights into the fundamental dynamics of SARS-CoV-2 mutations within patients and during transmission events.

These results support other ongoing research projects aiming at a better understanding and controlling the pandemic.
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Vaping does not appear to pose any significant additional risk of SARS-CoV-2 transmission

11/24/20


https://www.news-medical.net/news/20201 ... ssion.aspx


Researchers in Mexico, New Zealand and Italy have conducted a modeling study suggesting that the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) being transmitted via indoor vaping is not significantly higher than the risk associated with other types of expiration.

SARS-CoV-2 is the agent responsible for the current COVID-19 pandemic that continues to sweep the globe devastating public health and the worldwide economy.

Compared with exposure to regular breathing (without vaping) within the indoor environment, exposure to low-intensity expirations from an infectious vaper only increased the risk of transmission by an additional 1%.

The relative added risk was greater for high-intensity vaping but was not as high as the added risk associated with speaking or coughing.


“Vaping is an intermittent respiratory activity whose characteristic velocities, droplet diameters and emission rates are comparable to those of breathing and lesser than those of speaking, coughing or sneezing,” write Roberto Sussman from the National Autonomous University of Mexico in Mexico City and colleagues from Myriad Pharmaceuticals Limited in Auckland and the University of Catania in Italy.

“This implies that in a shared indoor space, vaping only adds a minuscule extra contagion risk to risks already existent from rest breathing and other respiratory activities.”

A pre-print version of the paper is available on the medRxiv* server while the article undergoes peer review.

Studying the aerial transmission of SARS-CoV-2

The evolution of bioaerosols transmitting disease via respiratory droplets has already been widely studied. The COVID-19 pandemic has therefore triggered researchers to study the aerial transmission of SARS-CoV-2 via various expiratory activities, including breathing, whispering, speaking, singing, coughing, and sneezing.

Now, Sussman and team have investigated the likelihood that SARS-CoV-2 transmission could occur via a different expiratory route: exhaled e-cigarette aerosol (ECA).

“While there is currently no factual evidence that pathogens have been spread through this route, it is entirely plausible that this should occur,” they write.

What did the researchers do?

The team conducted a comprehensive study investigating the risk of contagious respiratory droplets carried by exhaled ECA, posing a risk to bystanders.

Vaping styles were divided into two main categories: the majority style (80-90 %) was low-intensity “mouth to lung” (MTL) vaping, and the minority style was high-intensity “direct to lung” (DTL) vaping.

Modeling of exhaled ECA flow showed that MTL vaping should emit an average of 2 to 230 droplets per puff across a distance of 1.0 to 2.0 meters, while DTL vaping should emit several hundred to 1,000 droplets per puff across a distance of 2.0 meters

The team estimated the relative SARS-CoV-2 contagion risk of indoor vaping (an intermittent expiratory activity) in the home and restaurant setting, compared with rest breathing - a continuous expiratory activity that can be considered a “control case” scenario.

What were the study findings?

Compared with rest breathing, low-intensity MTL vaping (160 daily puffs) only increased the relative risk of SARS-CoV-2 transmission by 1%. For high-intensity DTL vaping (160 daily puffs) the added risk was between 5 and 17 %.

For speaking 10% of the time (6 mins per hour), the added risk increased to 44%, and for speaking 40% of the time (20 mins per hour), the added risk increased to 90%. For exposure to coughing, the added risk increased to more than 260%.

What does the team advise?

Sussman and colleagues say the risk for COVID-19 contagion from indoor vaping expirations does exist and should be considered.


“As far as protection against SARS-CoV-2 virus is concerned, vaping in a home scenario or social spaces does not require special extra interventions besides those already recommended for the general population: social distance and wearing face masks,” write the researchers.

“Vapers should be advised to be alert to the worries and fears of non-vapers when sharing indoor spaces or dwellings or when close to other citizens, and for safety measures to use low-powered devices for low intensity vaping. Vapers, however, deserve the same sensitivity, courtesy, and tolerance,” advises the team.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

However, this risk must be kept in perspective with respect to the risk posed by other expiratory activities.
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Researchers conduct aerosol characterization experiments to protect healthcare workers from COVID-19

11/24/20


https://www.news-medical.net/news/20201 ... ID-19.aspx


The rapid spread of COVID-19 overwhelmed hospitals that were unable to contend with the increasing number of patients, many requiring ventilators and other critical care. Such conditions can put medical workers at risk. Now researchers are studying methods to increase hospital safety and efficacy during the pandemic.

A shortage of life-saving ventilators, which typically cost around $30,000 each, hit hospitals particularly hard.

"By building a simple and cheap ventilator, we can help alleviate this burden for the medical staff," said Mohamed Amine Abassi, a PhD student in fluid mechanics.

Based on a prototype designed by his advisor, engineering professor Xiaofeng Liu, Abassi spearheaded an effort with colleagues from San Diego State University and the University of California San Diego to build such a device from readily available parts--plastic tubing, pressure valves, humidifier--and an air supply. Then they tested it.

Preliminary results shared at the 73rd Annual Meeting of the American Physical Society's Division of Fluid Dynamics suggest the ventilator meets essential requirements set by the Food and Drug Administration. It is fully controllable on three parameters--air pressure, inspiration time, and Positive End Expiratory Pressure (PEEP)--with plans for more controls in the works.

Abassi and Liu foresee the ventilators assisting not just overwhelmed hospitals in the United States but also in developing countries and rural areas with limited medical infrastructure. "If they can build it at home, they can use it," said Abassi. "And you can build many of these ventilators in a very short time."

Patients on ventilators who have some pulmonary conditions relevant to COVID-19 with underlying chronic lung diseases will often receive drugs like albuterol through an endotracheal tube. This treatment relaxes the bronchial muscles and improves airflow to the constricted lung airways.

A group from Lehigh University and the University of Arkansas for Medical Sciences sought the most effective methods for administering albuterol via ventilator.

Ariel Berlinski and his group conducted aerosol characterization experiments at the University of Arkansas. Rahul Rajendran at Lehigh used the results to investigate drug delivery through computations.

"The research objective was to evaluate the efficiency of drug delivery when the nebulizer type and its placement were varied in the ventilator circuit," said Arindam Banerjee, a member of the group and a Lehigh professor of mechanical engineering and mechanics.

The researchers found that a vibrating mesh (rather than a jet) nebulizer placed on the dry side of the humidifier delivers the highest dose to the lung. Administering albuterol through intubation works most effectively for smaller particles, while oral administration is more efficient for larger particles.

"Our results are vital for mechanical ventilator based treatment," said Banerjee.

Even in optimal circumstances, healthcare workers still risk contracting COVID-19. A new respiratory apparatus could reduce exhaled aerosols, which are known to transmit the virus that causes the disease.

Researchers from Liberty University and Vapotherm wondered how common respiratory treatments would affect aerosol emissions. So they decided to test a proposed design for a PVC face mask connected to suction, adding a high-velocity nasal insufflation cannula--the kind of tubed device that delivers oxygen to the nose.

Then, with input from medical experts, they modeled a hospital room with two patients and four caregivers using highly sophisticated computational techniques. According to their model, when patients wear the new apparatus, fewer particles reach the healthcare workers.

"It represents an inexpensive way to reduce the spread of airborne contagion using supplies commonly found in hospital rooms already," said engineering PhD candidate Reid Prichard. "This will remain an important tool even after the pandemic is over."

Another group from the University of South Florida, led by mechanical engineering PhD student Anthony Perez, is investigating what happens to any aerosol contaminants that patients do emit into a hospital isolation room--and how quickly the contaminants leave the room.

"As many hospitals are reaching capacity, ensuring a hospital room is safe to enter after an aerosol-generating procedure--or after the removal of a previous patient so hygiene workers can prepare the room--requires significant down time," said Perez.

According to the researchers, the Centers for Disease Control and Prevention ventilation recommendations assume pathogen-containing aerosols are perfectly mixed within a room. Using numerical simulations, the group finds that imperfect mixing conditions significantly affect how quickly ventilation removes pathogens from a room.

"It is both surprising and somewhat concerning that the standard for air sanitization is based on what many would consider a back-of-an-envelope calculation," said Perez.

The simulations suggest aerosol contaminants can linger in "dead zones" for around 10 minutes in a typical hospital isolation room. Meanwhile, "short circuits" expel some packets of contaminants quickly before they can disperse.

" Our research illustrates the need for a more accurate, yet inexpensive, framework for the prediction of aerosol concentrations in an arbitrary hospital room, especially in assessing the level of exposure of healthcare workers."

- Anthony Perez, PhD Student, Department of Mechanical Engineering, University of South Florida
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Re: Aerosolized Transmission

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Study shows how airflow inside a car may affect risk of COVID-19 transmission

12/7/20


https://www.news-medical.net/news/20201 ... ssion.aspx


If you find yourself in a car with someone outside your household during the COVID-19 pandemic, your instinct may be to roll down your window, whether you're the driver or a back-seat passenger.

But a University of Massachusetts Amherst physicist has shown in a new study that opening the car window closest to you isn't always the best option to protect yourself from coronavirus or any airborne infection.

In a paper published Dec. 4 in the journal Science Advances, researchers have revealed certain surprising ways in which the airflow patterns within a car's interior could either heighten or suppress the risk of airborne infection during everyday commutes.

"One might imagine that people instinctively open windows right beside them while riding with a co-passenger during the pandemic. That may not be optimal - though it's better than opening no window," says lead author Varghese Mathai, an assistant professor of physics at UMass Amherst.

He explains, "We designed this research with ride-sharing in mind, from a traditional taxi or Uber and Lyft to noncommercial commutes, assuming a driver and one passenger, seated in the back on the passenger side to provide the best possible spacing between the occupants."

Briefly, the research suggests that opening the windows farthest from the driver and the back-seat passenger might offer some benefits. The findings may provide COVID-19 risk reduction measures for the hundreds of millions of people driving in passenger cars or taking a taxi worldwide.

The most and least risky scenarios for airborne pathogen transmission in a car are understood by scientists: Opening all the windows, along with bringing in fresh air through the vents, is thought to create the best in-cabin environment to reduce the risk of transmission by increasing ventilation. Keeping all the windows up and using only the recirculating air mode is likely the riskiest option.

Realizing the impracticalities of keeping all car windows open in winter or rainy weather, Mathai wanted to examine what happens to aerosolized particles exhaled by occupants inside the car's cabin under various configurations of open and closed windows.

"These tiny, potentially pathogenic particles remain in the air for long durations without settling down, so if they are not flushed out of the cabin, they can build up over time posing an increased risk of infection," he explains.

Generally, the air flowing around a car creates a lower pressure on the front windows as compared to the back windows, Mathai says.


" We had this idea that if you open the rear and front windows on opposite sides, then you might create an air current from the rear to the front of the cabin, and crossing through the middle."

- Varghese Mathai, Study Lead Author and Assistant Professor of physics, University of Massachusetts Amherst

The study was conducted with colleagues Asimanshu Das, Jeffrey Bailey, and Kenneth Breuer at Brown University, where Mathai worked previously and started the study. The researchers hypothesized that if all windows can't be left open, opening the front window on the right side and the rear window on the left side might best protect the driver and passenger from the hundreds of aerosol particles released in every human breath.

"To our surprise, the simulations showed an air current that acts like a barrier between the driver and the passenger," says Mathai, who likened this phenomenon to the air curtain created by a draft blown down vertically at some supermarket entrances, which prevents outdoor air from mixing with indoor air, even if the entrance door is open.

"While these measures are no substitute for wearing a face mask while inside a car, they can help reduce the pathogen load inside the very confined space of a car cabin," he points out.

Like many other researchers during the pandemic, Mathai -- an experimental physicist -- decided to shift his focus toward computer simulations while working from home. He later backed up his findings using smoke visualization and field tests that identified low-speed and high-speed zones inside the car.

The research describes the driver-to-passenger and passenger-to-driver transmission for different ventilation options and used passive scalar transport as a proxy for infectious particles. Heat maps illustrate the scalar concentration fields originating from either the driver or passenger.

The researchers used a simplified, time-averaged model for the turbulent air flow, and study implications are limited to the airborne mode of transmission, the author's stress. The computer model was based roughly on the exterior of a Toyota Prius driven at around 50 mph and the field tests of smoke and flow wand were recorded in the cabin of a Kia Optima.

Source:


University of Massachusetts Amherst

Journal reference:

Mathai, V., et al. (2020) Airflows inside passenger cars and implications for airborne disease transmission. Science Advances. doi.org/10.1126/sciadv.abe0166.
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Re: Aerosolized Transmission

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Study offers suggestions for reducing risk of COVID-19 transmission in car's ventilation system

12/7/20


https://www.news-medical.net/news/20201 ... ystem.aspx


A new study of airflow patterns inside a car's passenger cabin offers some suggestions for potentially reducing the risk of COVID-19 transmission while sharing rides with others.

The study, by a team of Brown University researchers, used computer models to simulate the airflow inside a compact car with various combinations of windows open or closed. The simulations showed that opening windows -- the more windows the better -- created airflow patterns that dramatically reduced the concentration of airborne particles exchanged between a driver and a single passenger.

Blasting the car's ventilation system didn't circulate air nearly as well as a few open windows, the researchers found.

" Driving around with the windows up and the air conditioning or heat on is definitely the worst scenario, according to our computer simulations. The best scenario we found was having all four windows open, but even having one or two open was far better than having them all closed."

- Asimanshu Das, Study Co-Lead Author and Graduate Student, School of Engineering, Brown University

Das co-led the research with Varghese Mathai, a former postdoctoral researcher at Brown who is now an assistant professor of physics at the University of Massachusetts, Amherst. The study is published in the journal of Science Advances.

The researchers stress that there's no way to eliminate risk completely -- and, of course, current guidance from the U.S. Centers for Disease Control (CDC) notes that postponing travel and staying home is the best way to protect personal and community health. The goal of the study was simply to study how changes in airflow inside a car may worsen or reduce the risk of pathogen transmission.

The computer models used in the study simulated a car, loosely based on a Toyota Prius, with two people inside -- a driver and a passenger sitting in the back seat on the opposite side from the driver.

The researchers chose that seating arrangement because it maximizes the physical distance between the two people (though still less than the 6 feet recommended by the CDC). The models simulated airflow around and inside a car moving at 50 miles per hour, as well as the movement and concentration of aerosols coming from both driver and passenger.

Aerosols are tiny particles that can linger in the air for extended periods of time. They are thought to be one way in which the SARS-CoV-2 virus is transmitted, particularly in enclosed spaces.

Part of the reason that opening windows is better in terms of aerosol transmission is that it increases the number of air changes per hour (ACH) inside the car, which helps to reduce the overall concentration of aerosols. But ACH was only part of the story, the researchers say.

The study showed that different combinations of open windows created different air currents inside the car that could either increase or decrease exposure to remaining aerosols.

Because of the way air flows across the outside of the car, air pressure near the rear windows tends to be higher than the pressure at the front windows. As a result, air tends to enter the car through the back windows and exit through the front windows.

With all the windows open, this tendency creates two more-or-less independent flows on either side of the cabin. Since the occupants in the simulations were sitting on opposite sides of the cabin, very few particles end up being transferred between the two.

The driver in this scenario is at slightly higher risk than the passenger because the average airflow in the car goes from back to front, but both occupants experience a dramatically lower transfer of particles compared to any other scenario.

The simulations for scenarios in which some but not all windows are down yielded some possibly counterintuitive results. For example, one might expect that opening windows directly beside each occupant might be the simplest way to reduce exposure.

The simulations found that while this configuration is better than no windows down at all, it carries a higher exposure risk compared to putting down the window opposite each occupant.

"When the windows opposite the occupants are open, you get a flow that enters the car behind the driver, sweeps across the cabin behind the passenger and then goes out the passenger-side front window," said Kenny Breuer, a professor of engineering at Brown and a senior author of the research. "That pattern helps to reduce cross-contamination between the driver and passenger."

It's important to note, the researchers say, that airflow adjustment are no substitute for mask-wearing by both occupants when inside a car. And the findings are limited to potential exposure to lingering aerosols that may contain pathogens. The study did not model larger respiratory droplets or the risk of actually becoming infected by the virus.

Still, the researchers say the study provides valuable new insights into air circulation patterns inside a car's passenger compartment -- something that had received little attention before now.

"This is the first study we're aware of that really looked at the microclimate inside a car," Breuer said. "There had been some studies that looked at how much external pollution gets into a car, or how long cigarette smoke lingers in a car. But this is the first time anyone has looked at airflow patterns in detail."

The research grew out of a COVID-19 research task force established at Brown to gather expertise from across the University to address widely varying aspects of the pandemic. Jeffrey Bailey, an associate professor of pathology and laboratory medicine and a co-author of the airflow study, leads the group.

Bailey was impressed with how quickly the research came together, with Mathai suggesting the use of computer simulations that could be done while laboratory research at Brown was paused for the pandemic.

"This is really a great example of how different disciplines can come together quickly and produce valuable findings," Bailey said. "I talked to Kenny briefly about this idea, and within three or four days his team was already doing some preliminary testing. That's one of the great things about being at a place like Brown, where people are eager to collaborate and work across disciplines."

Source:

Brown University

Journal reference:

Mathai, V., et al. (2020) Airflows inside passenger cars and implications for airborne disease transmission. Science Advances. doi.org/10.1126/sciadv.abe0166.
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