State governments such as Pennsylvania also recommend that people wear face coverings when in public venues.
This is not a contradiction, or a flip flop, but rather an understanding of how the situation has changed with a growing number of cases in the US. As more become infected, this increases the likelihood of asymptomatic or pre-symptomatic people in settings where they can spread the virus through aerosolization. By wearing a face covering, it reduces the risk that the wearer will spew out significant aerosols.
These are the cloth or homemade masks, not the surgical or N-95 masks which should be reserved for those working in the medical field or other high risk operations.
https://www.fda.gov/food/food-safety-during-emergencies/food-safety-and-coronavirus-disease-2019-covid-19
Should employees in retail food and food production settings wear face coverings to prevent exposure to COVID-19? (Posted April 4, 2020)
On April 3, the CDC released an updated recommendation regarding the use of cloth face coverings to help slow the spread of COVID-19. CDC recommends the use of simple cloth face coverings as a voluntary public health measure in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies).
For workers on farms, and in food production, processing, and retail settings who do not typically wear masks as part of their jobs, consider the following if you choose to use a cloth face covering to slow the spread of COVID-19:
- Maintain face coverings in accordance with parameters in FDA’s Model Food Code sections 4-801.11 Clean Linens and 4.802.11 Specifications.
- Launder reusable face coverings before each daily use.
- CDC also has additional information on the use of face coverings, including washing instructions and information on how to make homemade face covers.
CDC New Release
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html
Recommendation Regarding the Use of Cloth Face Coverings, Especially in Areas of Significant Community-Based Transmission
CDC continues to study the spread and effects of the novel coronavirus across the United States. We now know from recent studies that a significant portion of individuals with coronavirus lack symptoms (“asymptomatic”) and that even those who eventually develop symptoms (“pre-symptomatic”) can transmit the virus to others before showing symptoms. This means that the virus can spread between people interacting in close proximity—for example, speaking, coughing, or sneezing—even if those people are not exhibiting symptoms. In light of this new evidence, CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission.
It is critical to emphasize that maintaining 6-feet social distancing remains important to slowing the spread of the virus. CDC is additionally advising the use of simple cloth face coverings to slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others. Cloth face coverings fashioned from household items or made at home from common materials at low cost can be used as an additional, voluntary public health measure.
The cloth face coverings recommended are not surgical masks or N-95 respirators. Those are critical supplies that must continue to be reserved for healthcare workers and other medical first responders, as recommended by current CDC guidance.
This recommendation complements and does not replace the President’s Coronavirus Guidelines for America, 30 Days to Slow the Spread, which remains the cornerstone of our national effort to slow the spread of the coronavirus. CDC will make additional recommendations as the evidence regarding appropriate public health measures continues to develop.
Science Daily
https://www.sciencedaily.com/releases/2020/04/200403162709.htm
Science News from research organizations
How important is speech in transmitting coronavirus?
Date:
April 3, 2020
Source:
University of California - Davis
Summary:
Normal speech by individuals who are asymptomatic but infected with coronavirus may produce enough aerosolized particles to transmit the infection, according to aerosol scientists. Although it's not yet known how important this is to the spread of COVID-19, it underscores the need for strict social distancing measures -- and for virologists, epidemiologists and engineers who study aerosols and droplets to work together on this and other respiratory diseases.
Normal speech by individuals who are asymptomatic but infected with coronavirus may produce enough aerosolized particles to transmit the infection, according to aerosol scientists at the University of California, Davis. Although it's not yet known how important this is to the spread of COVID-19, it underscores the need for strict social distancing measures -- and for virologists, epidemiologists and engineers who study aerosols and droplets to work together on this and other respiratory diseases.
Aerosols are particles small enough to travel through the air. Ordinary speech creates significant quantities of aerosols from respiratory particles, said William Ristenpart, professor of chemical engineering at UC Davis. Ristenpart is co-author on an editorial about the problem to be published in the journal Aerosol Science and Technology.
These respiratory particles are about one micron, or one micrometer, in diameter. That's too small to see with the naked eye, but large enough to carry viruses such as influenza or SARS-CoV-2.
Some individuals superemitters
Last year, Ristenpart, graduate student Sima Asadi and colleagues published a paper showing that the louder one speaks, the more particles are emitted and that some individuals are "superemitters" who give off up to 10 times as many particles as others. The reasons for this are not yet clear. In a follow-up study published in January in PLOS One, they investigated which speech sounds are associated with the most particles.
Calculating just how easily a virus like SARS-CoV-2 spreads through droplets requires expertise from different fields. From virology, researchers need to know how many viruses are in lung fluids, how easily they form into droplets and how many viruses are needed to start an infection. Aerosol scientists can study how far droplets travel once expelled, how they are affected by air motion in a room and how fast they settle out due to gravity.
"The aerosol science community needs to step up and tackle the current challenge presented by COVID-19, and also help better prepare us for inevitable future pandemics," Ristenpart and colleagues conclude.
Other authors on the editorial are Asadi; Professor Anthony Wexler, UC Davis Department of Mechanical and Aerospace Engineering; and Nicole Bouvier, Icahn School of Medicine at Mount Sinai.
Science. 2020 Mar 16. pii: eabb3221. doi: 10.1126/science.abb3221. [Epub ahead of print]
Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2).
Li R#1, Pei S#2, Chen B#3, Song Y4, Zhang T5, Yang W6, Shaman J2.
Abstract
Estimation of the prevalence and contagiousness of undocumented novel coronavirus (SARS-CoV2) infections is critical for understanding the overall prevalence and pandemic potential of this disease. Here we use observations of reported infection within China, in conjunction with mobility data, a networked dynamic metapopulation model and Bayesian inference, to infer critical epidemiological characteristics associated with SARS-CoV2, including the fraction of undocumented infections and their contagiousness. We estimate 86% of all infections were undocumented (95% CI: [82%-90%]) prior to 23 January 2020 travel restrictions. Per person, the transmission rate of undocumented infections was 55% of documented infections ([46%-62%]), yet, due to their greater numbers, undocumented infections were the infection source for 79% of documented cases. These findings explain the rapid geographic spread of SARS-CoV2 and indicate containment of this virus will be particularly challenging.
Copyright © 2020, American Association for the Advancement of Science.
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