Aerosolized Transmission

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Re: Aerosolized Transmission

Post by trader32176 »

NO SHOUTING: California theme parks ban people from screaming in rides to prevent coronavirus spread

3/19/21 ... rides.html

Theme parks in California will limit patrons’ screaming or shouting on rides to curb the spread of COVID-19. A union of amusement parks in the state proposed the measure in a list of actions they would take to safely reopen these leisure facilities in line with a state blueprint.

The California Attractions and Parks Association (CAPA) shared a list of steps its member amusement parks would be taking to safely reopen their properties to the public. It drafted the list with the hope of better following the state’s blueprint for determining COVID-19 risk. According to CAPA, member parks “have been busy planning and preparing to implement their own site-specific plans for reopening.”

Theme parks to limit activities known to cause the spread of COVID-19

CAPA’s plan detailed how amusement parks and attractions can reopen “in limited capacity with the proper modifications.” Limiting activities and environments that are known to cause increased COVID-19 transmission and require people to raise their voices was among the points indicated in the plan.

To address concerns about the virus’ spread, amusement park operators will require the use of face masks or face coverings for park ride passengers. Seat loading patterns on rides will also be modified “to mitigate the effects of shouting.” CAPA also remarked that guests ought to “generally face in one direction” on rides to minimize excess noise. The association also added it will only sit people from the same party for various rides and attractions to prevent mixing and mingling of amusement park visitors. CAPA explained that amusement parks “do not encourage congregations” as families stay within their own household group when visiting.

Furthermore, the CAPA list also says that amusement parks will provide designated eating and drinking areas where people can remove their masks. Eating on the go will no longer be allowed as guests will be required to wear face coverings while walking around.

New regulations in line with theme park re-openings in California

CAPA published the reopening action plan as a spike in coronavirus cases in the winter rapidly tapered off. California officials announced in early March that reopening criteria for theme parks and outdoor stadiums would be relaxed starting April 1.

Theme parks will only be allowed to re-open if the county they are located in drops below California’s restrictive coronavirus tier. They will also be permitted to re-open albeit initially at 15 percent capacity, and the parks will be open only to California residents.

Disneyland was among the theme parks in the state aiming to reopen soon. The “happiest place on Earth” has joined other amusement park operators and local officials in pressuring state authorities to permit swift re-opening. Disney CEO Bob Chapek said the previous week that the park was targeting a late April 2021 re-opening after the state eased COVID-19 restrictions.

The theme park in Anaheim, located near Los Angeles, has been closed for almost exactly a year – while other Disney resorts worldwide have re-opened their doors. Based on previous guidance, theme parks would be among the last places to re-open in California. But the projection has not dissuaded Chapek. “Here in California, we’re encouraged by the positive trends we’re seeing. [We’re] hopeful they’ll continue to improve and we’ll be able to reopen our parks to guests with limited capacity by late April,” he said. (Related: Disneyland converted into mass COVID-19 vaccination site.)

The Disney CEO cautioned that the park could not reopen on April 1, the date originally eyed for resumption. He explained that it would take time to recall more than 10,000 furloughed staff members and to retrain them in pandemic safety measures. Chapek added that a precise opening date would be confirmed “in the coming weeks.” (Related: Disney to lay off 28,000 workers in belt-tightening move amid coronavirus pandemic.)

Soon enough, Disneyland posted on its Twitter account that it would reopen its doors on April 30. In a March 17 tweet, the park said it plans to officially reopen with limited capacity, and only for California residents.
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Re: Aerosolized Transmission

Post by trader32176 »

Thermo Fisher Scientific launches in-air SARS-CoV-2 surveillance solution

4/8/21 ... ution.aspx

Thermo Fisher Scientific Inc., the world leader in serving science, today announced the launch of the Thermo Scientific AerosolSense Sampler, a new surveillance solution designed to deliver fast and highly reliable insight into the presence of in-air pathogens, including SARS-CoV-2.

Individual testing will continue to be a cornerstone in the COVID-19 pandemic response because it enables and informs clinical diagnoses, patient triage and treatment decisions. As society returns to pre-pandemic activities, expanded and complementary monitoring of environments will be key in providing useful insights into virus presence. The AerosolSense Sampler is the next step in providing institutions with highly reliable information to help keep their employees and the public safe.

The AerosolSense Sampler is an in-air pathogen surveillance solution, which collects representative aerosol samples of ambient air and traps in-air pathogens on a collection substrate. The sample can be readily analyzed through subsequent laboratory testing using polymerase chain reaction (PCR) methodology. Confirming the presence of pathogens like SARS-CoV-2 in a space during a known time interval enables decision makers in hospitals and other indoor facilities to take actions to protect their employees and provide the public with confidence.

" Such factors as emerging variants, semi-vaccinated populations and varying levels of compliance with COVID-19 personal safety protocols, continue to pose risks to a society looking to return to life as it was before the pandemic. It is important that easy-to-use, highly reliable solutions be available to allow hospitals, nursing homes, schools, businesses and government institutions to identify the presence of in-air pathogens quickly, so safety protocols can be put into action, validated, or strengthened."

- Mark Stevenson, Executive vice president and chief operating officer, Thermo Fisher Scientific

Dr. John Broach, assistant professor of Emergency Medicine at the University of Massachusetts and an early user of the AerosolSense Sampler said, "Monitoring the efficacy of infection control practices is invaluable to protecting health care providers on the frontlines. Combatting COVID-19 is a multi-front battle, and this surveillance solution can be implemented seamlessly within institutions to alert them to the presence of SARS-CoV-2, so that they can take appropriate steps to prevent its spread."

Thermo Fisher designed the AerosolSense Sampler to capture a wide variety of in-air pathogens and has specifically validated it for the SARS-CoV-2 pathogen.


Thermo Fisher Scientific Inc.
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Re: Aerosolized Transmission

Post by trader32176 »

Researchers assess SARS-CoV-2 transmission risk during air travel

4/15/21 ... study.aspx

A team of scientists from the United States recently conducted a meta-analysis to estimate the risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during air travel. The findings reveal that even with SARS-CoV-2-infected persons onboard, the risk of viral transmission is low inside an aircraft. The study is currently available on the medRxiv* preprint server.


As of April 15, 2021, globally, there have been 136 million confirmed cases of coronavirus disease 2019 (COVID-19), including 2.9 million deaths, registered to the World Health Organization (WHO). At the initial phase of the pandemic, strict control measures applied to control the viral transmission have severely impacted the socioeconomic status of many countries globally. Because of national and international travel restrictions, the aviation industries have faced an almost 95% drop in passenger numbers during the initial phase of the pandemic.

As the pandemic progresses, the aviation-related services of many countries have been resumed to boost the global economy. This gives rise to global concerns about the risk of SARS-CoV-2 transmission among passengers traveling by air across the globe.

Viral transmission due to air travel can occur in two ways. A passenger with SARS-CoV-2 infection traveling via aircraft to a new location can transmit COVID-19 either on the ground or inside the aircraft.

In the current study, the scientists estimated the risk of SARS-CoV-2 transmission from an infected person to fellow passengers inside an aircraft.

Study design

The scientists conducted a systemic review of the present literature to estimate the number of index patients and secondary COVID-19 cases related to air travel between January 2020 and September 2020. An index patient refers to a passenger who was infected before air travel. A secondary COVID-19 case refers to the passenger who became infected from the index patient during air travel.

Because the primary focus of most of the published studies was infected passengers, the current risk estimation was limited to flights with index patients and did not involve the transmission risks among aircrew, ground crews, and airport staff.

The scientists estimated the risk of viral transmission using a quantitative approach that considered secondary cases and the total number of passengers inside an aircraft. The data collected from published literature were corrected for known data limitations, such as asymptomatic and underreported COVID-19 cases. Moreover, because COVID-19 testing and reporting processes vary across different locations/countries, uncertainties were also included in the risk calculation to obtain the most accurate risk estimation.

Important observations

According to the study findings, about 1.4 billion passengers traveled by air between January 2020 and September 2020. Among all air travelers, 2,866 were identified as index patients, and 44 were identified as potential secondary COVID-19 cases.

For estimating the risk of transmission during air travel, the scientists hypothesized that all possible transmissions occurred inside the aircraft cabin; however, they mentioned that in some cases, the transmission could have occurred elsewhere, such as in the airport.

Available literature on in-flight transmission

In a London-Hanoi flight on March 2, 2020, 15 secondary COVID-19 cases were identified. However, based on the duration between flight arrival and a positive SARS-CoV-2 test result, the scientists hypothesized that all these passengers were infected after the completion of air travel.

Furthermore, in a Singapore to Hangzhou, China flight on January 24, 2020, 15 index patients and only a single secondary COVID-19 case were identified. With further analysis, the scientists observed that except for eating food and drinking water, all 16 passengers wore masks throughout the air travel. However, the secondary case did not wear a mask properly when sitting in an unassigned seat surrounded by infected symptomatic passengers.

Estimated risk of in-flight transmission

By including all data correction factors in the calculations, the scientists estimated that the risk of SARS-CoV-2 transmission inside an aircraft cabin is 1 in 1.7 million. Furthermore, using the uncertainty estimates of publicly available literature, they estimated that the risk of in-flight transmission ranges from 1 case in every 712,000 passengers to 1 case in every 8 million passengers.

Study significance

The study reveals that the risk of SARS-CoV-2 transmission inside an aircraft cabin is as low as 1 case in 1.7 million passengers. In other words, the study findings indicate that even with index patients onboard, the overall risk of acquiring secondary infection is low during air travel.

Improved environmental control measures inside an aircraft cabin, such as high airflow, high-quality air purification, and seating arrangements, are believed to play a significant role in reducing the risk of viral transmission among passengers.

*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.

Journal reference:

Pang JK. 2021. Probability and Estimated Risk of SARS-CoV-2 Transmission in the Air Travel System: A Systemic Review and Meta-Analysis. MedRxiv. doi:, ... 21255171v1
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Re: Aerosolized Transmission

Post by trader32176 »

Future attempts to reduce Covid-19 spread should focus on tackling airborne transmission

4/15/21 ... ssion.aspx

Any future attempts to reduce the spread of covid-19 should be focused on tackling close airborne transmission of the virus which is considered to be the primary route for its circulation, according to experts in an editorial published in The BMJ.

Respiratory experts argue that it is now clear that covid-19 (SARS-CoV-2) is most likely to transmit between people at close range through inhalation rather than through contact with surfaces or longer range airborne routes, although those routes can also be responsible.

The covid-19 pandemic has helped to redefine airborne transmission of viruses, say the experts from the universities of Leicester, Edinburgh Napier and Hong Kong, Virginia Tech, and NHS Lanarkshire, Edinburgh.

There has been some confusion over precise definitions of air transmissions of infections from the last century in which the difference between “droplet” “airborne,” and “droplet nuclei” transmission have led to misunderstandings over the physical behavior of these particles, they say.

What is important to know, they claim, is that if a person can inhale particles, regardless of their size or name, they are breathing in aerosols. And while this can happen at long range, it is more likely to happen when being close to someone because the aerosols between two people are much more concentrated at short range, similar to being close to someone who is smoking.

People infected with SARS-CoV-2 produce many small respiratory particles full of the virus as they exhale. Some of these will be inhaled almost immediately by those within a typical conversational “short range” distance of less than one meter, say the experts, while the remainder will disperse over longer distances to be inhaled by others further away – more than two metres.

The well-known and often used preventative steps of wearing masks, keeping your distance, and reducing indoor occupancy all help to reduce the usual routes of transmission, whether through direct contact with surfaces or droplets, or from inhaling aerosols, they say.

However, they argue that a crucial difference is the need for added emphasis on ventilation because the tiniest suspended particles can remain in the air for hours and these are an important route of transmission.

Therefore measures to ensure that air is replaced or cleaned are all the more important, meaning opening windows, installing or upgrading heating, ventilation, and use of air conditioning systems.

In addition, the quality of masks is important to ensure effective protection against inhaled aerosols. Masks usually prevent large droplets from landing on covered areas of the face but tiny airborne particles can find their way around any gaps.

High quality masks with high filtration efficiency and a good fit are, therefore, important, they say.

Efforts to improve the quality of indoor air through better ventilation will bring other benefits, they add, such as reduced sick leave for other respiratory viruses and other environmentally related complaints including allergies and sick building syndrome.

If companies experienced less absenteeism with its impact on productivity, this could save them significant costs which would offset the expense of upgrading their ventilation systems.

The experts conclude: “Covid-19 may well become seasonal, and we will have to live with it as we do with influenza. So governments and health leaders should heed the science and focus their efforts on airborne transmission.

“Safer indoor environments are required, not only to protect unvaccinated people and those for whom vaccines fail, but also to deter vaccine resistant variants or novel airborne threats that may appear at any time.

“Improving indoor ventilation and air quality, particularly in healthcare, work, and educational environments, will help all of us to stay safe, now and in the future.”



Journal reference:

Tang, J.W., et al. (2021) Covid-19 has redefined airborne transmission. BMJ.
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Re: Aerosolized Transmission

Post by trader32176 »

A new approach to estimate the risks of exposure to COVID-19 under different indoor settings

4/16/21 ... tings.aspx

Two MIT professors have proposed a new approach to estimating the risks of exposure to Covid-19 under different indoor settings.

The guideline they developed suggests a limit for exposure time, based on the number of people, the size of the space, the kinds of activity, whether masks are worn, and the ventilation and filtration rates. Their model offers a detailed, physics-based guideline for policymakers, businesses, schools, and individuals trying to gauge their own risks.

The guideline, appearing this week in the journal PNAS, was developed by Martin .Z. Bazant, professor of chemical engineering and applied mathematics, and John W. M. Bush, professor of applied mathematics. They stress that one key feature of their model, which has received less attention in existing public-health policies, is providing a specific limit for the amount of time a person spends in a given setting.

Their analysis is based on the fact that in enclosed spaces, tiny airborne pathogen-bearing droplets emitted by people as they talk, cough, sneeze, sing, or eat will tend to float in the air for long periods and to be well-mixed throughout the space by air currents.

There is now overwhelming evidence, they say, that such airborne transmission plays a major role in the spread of Covid-19. Bush says the study was initially motivated early last year by their concern that many decisions about policies were being guided primarily by the "6-foot rule," which doesn't adequately address airborne transmission in indoor spaces.

Using a strictly quantitative approach based on the best available data, the model produces an estimate of how long, on average, it would take for one person to become infected with the SARS-CoV-2 virus if an infected person entered the space, based on the key set of variables defining a given indoor situation.

Rather than a simple yes or no answer about whether a given setting or activity is safe, it provides a guide as to just how long a person could safely expect to engage in that activity, whether it be a few minutes in a store, an hour in a restaurant, or several hours a day in an office or classroom, for example.

" As scientists, we've tried to be very thoughtful and only go with what we see as hard data. We've really tried to just stick to things we can carefully justify. We think our study is the most rigorous study of this type to date. While new data are appearing every day, and many uncertainties remain about the SARS-CoV-2 virus' transmission. We feel confident that we've made conservative choices at every point."

- Martin .Z. Bazant, Professor of Chemical Engineering and Applied Mathematics, Massachusetts Institute of Technology

Bush adds: "It's a quickly moving field. We submit a paper and the next day a dozen relevant papers come out, so we scramble to incorporate them. It's been like shooting at a moving target." For example, while their model was initially based on the transmissibility of the original strain of SARS-CoV-2 from epidemiological data on the best characterized early spreading events, they have since added a transmissibility parameter, which can be adjusted to account for the higher spreading rates of the new emerging variants. This adjustment is based on how any new strain's transmissibility compares to the original strain; for example, for the U.K. strain, which has been estimated to be 60 percent more transmissible than the original, this parameter would be set at 1.6.

One thing that's clear, they say, is that simple rules, based on distance or capacity limits on certain types of businesses, don't reflect the full picture of the risk in a given setting. In some cases that risk may be higher than those simple rules convey; in others it may be lower. To help people, whether policymakers or individuals, to make more comprehensive evaluations, the researchers teamed with app developer Kasim Khan to put together an open-access mobile app and website where users can enter specific details about a situation -- size of the space, number of people, type of ventilation, type of activity, mask wearing, and the transmissibility factor for the predominant strain in the area at the time -- and receive an estimate of how long it would take, under those circumstances, for one new person to catch the virus if an infected person enters the space.

The calculations were based on inferences made from various mass-spreading events, where detailed data were available about numbers of people and their age range, sizes of the enclosed spaces, kinds of activities (singing, eating, exercising, etc.), ventilation systems, mask wearing, the amount of time spent, and the resulting rates of infections. Events they studied included, for example, the Skagit Valley Chorale in Washington state, where 86 percent of the seniors present became infected at a two-hour choir practice

While their guideline is based on well-mixed air within a given space, the risk would be higher if someone is positioned directly within a focused jet of particles emitted by a sneeze or a shout, for example. But in general the assumption of well-mixed air indoors seems to be consistent with the data from actual spreading events, they say.

"When you look at this guideline for limiting cumulative exposure time, it takes in all of the parameters that you think should be there -- the number of people, the time spent in the space, the volume of the space, the air conditioning rate and so on," Bush says. "All of these things are kind of intuitive, but it's nice to see them appear in a single equation."

While the data on the crucial importance of airborne transmission has now become clear, Bazant says, public health organizations initially placed much more emphasis on handwashing and the cleaning of surfaces. Early in the pandemic, there was less appreciation for the importance of ventilation systems and the use of face masks, which can dramatically affect the safe levels of occupancy, he says.

"I'd like to use this work to establish the science of airborne transmission specifically for Covid-19, by just taking into account all factors, the available data, and the distribution of droplets for different kinds of activities," Bazant says. He hopes the information will help people make informed decisions for their own lives: "If you understand the science, you can do things differently in your own home and your own business and your own school."

Bush offers an example: "My mother is over 90 and lives in an elder care facility. Our model makes it clear that it's useful to wear a mask and open a window -- this is what you have in your control." He was alarmed that his mother was planning to attend an exercise class in the facility, thinking it would be OK because people would be 6 feet apart. As the new study shows, because of the number of people and the activity level, that would actually be a highly risky activity, he says.

Already, since they made the app available in October, Bazant says, they have had about half a million users. Their feedback helped the researchers refine the model further, he says. And it has already helped to influence some decisions about reopening of businesses, he adds.

For example, the owner of an indoor tennis facility in Washington state that had been shut down due to Covid restrictions says he was allowed to reopen in January, along with certain other low-occupancy sports facilities, based on an appeal he made based in large part on this guideline and on information from his participation in Bazant's online course on the physics of Covid-19 transmission.

Bazant says that in addition to recommending guidelines for specific spaces, the new tools also provide a way to assess the relative merits of different intervention strategies. For example, they found that while improved ventilation systems and face mask use make a big difference, air filtration systems have a relatively smaller effect on disease spread. And their study can provide guidance on just how much ventilation is needed to reach a particular level of safety, he says.

"Bazant and Bush have provided a valuable tool for estimating (among other things) the upper limit on time spent sharing the air space with others," says Howard Stone, a professor of mechanical and aerospace engineering at Princeton University who was not connected to this work. While such an analysis can only provide a rough estimate, he says the authors "describe this kind of order of magnitude of estimate as a means for helping others judge the situation they might be in and how to minimize their risk. This is particularly helpful since a detailed calculation for every possible space and set of parameters is not possible."


Massachusetts Institute of Technology

Journal reference:

Bazant, M. Z & Bush, J. W. M., et al. (2021) A guideline to limit indoor airborne transmission of COVID-19. Proceedings of the National Academy of Sciences.
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