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America Can''t Afford to Lose More Black Male Doctors
译者:unknown     发布时间:2020-10-29     超过 0 位网友阅读


Coronavirus can float in air and WHO and CDC should tell people that, experts say
July 06, 2020



(CNN) Imagine a noisy, crowded bar. Music is pounding, and people are clustered close together, talking loudly or even shouting to be heard. If it''s cold out, doors and windows are shut tight and the heat is on, or if it''s hot out, everything is shut and the air conditioner is recirculating the air.


This, in Donald Milton''s opinion, is the perfect situation for spreading coronavirus.


Not only could people pass the virus directly from one to another in the little droplets that we all spray to one degree or another when we talk, laugh or sing; but those little droplets also go up into the air where, Milton says, they can float around for at least some time.


It''s not a secret, but agencies seem to be afraid to talk about the airborne nature of the virus, Milton said.


"The airborne transmission word seems to be loaded," Milton, one of two main authors of the letter, told CNN.


"The current guidance from numerous international and national bodies focuses on hand washing, maintaining social distancing, and droplet precautions," Milton and colleagues wrote in the letter, published in the journal Clinical Infectious Diseases.


"Most public health organizations, including the World Health Organization, do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people," they added.


''They don''t want to talk about airborne transmission because that is going to make people afraid''


"I guess we are hoping that WHO will come around and be more willing to acknowledge the important roles of aerosols, whether they want to call it airborne transmission or not," Milton said.


Milton studies the airborne transmission of viruses. The other main author, Lidia Morawska, is a professor of environmental engineering and an expert in aerosol science at the Queensland University of Technology in Brisbane, Australia. Milton said they and a group of other, similar experts have been discussing the potential airborne transmission of coronavirus since February.


Milton said the group wants to demystify the word so that health agencies will be less fearful about using it.


"The best vaccine against fear is knowledge and empowering people to take care of themselves," Milton said. "I want them to understand to what extent washing their hands is important. Why wearing a mask is important is because it blocks the aerosols at their source, when it is easy to block them." It''s harder to block aerosols once they are floating in the air, he said.


The virus is carried on droplets that come out of people''s mouths and noses, and the sizes of those droplets vary. Large droplets fall onto surfaces rapidly and can be picked up on fingers and carried to the eyes, nose or mouth. Smaller droplets can stay in the air longer, and can be inhaled more deeply into the lungs.


"There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission," Milton and his colleagues wrote.


"For example, at typical indoor air velocities, a 5 nanometre droplet will travel tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 metres (about five feet) to the floor."


What''s not clearly understood is how important droplet size is to coronavirus transmission, Milton said.


But studies show it''s a factor, Milton added. "A lot of people crowded close together indoors where it is poorly ventilated -- that is what drives the pandemic," he said. A loud bar, where people must raise their voices to be heard, is a perfect storm of close contact, poor air circulation and people generating a lot of virus-carrying particles by talking, laughing and shouting.


Advice to avoid coronavirus transmission


But Milton said there are other ways, too, including improved ventilation, as well as distancing and mask use. And that''s information the average person, as well as health care professionals, can use and act on.


"I am very much concerned about the general public and schools and ventilation in school buildings and in dorms on college campuses and in bars and in churches and where people sing and where people congregate," he said.


The group gives practical advice in its letter.


· Supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights. (These would be placed high up in the ceiling to avoid damage to people''s eyes and skin)


· Avoid overcrowding, particularly in public transport and public buildings.


"Such measures are practical and often can be easily implemented; many are not costly," they wrote.


"For example, simple steps such as opening both doors and windows can dramatically increase air flow rates in many buildings."


In a car, Milton advises, open windows and make sure the air conditioning or heat is not recirculated but set to include outside air.


In buildings, carbon dioxide monitors can help managers know if the air is being refreshed properly, Milton said. Outdoors in an urban area, he said, carbon dioxide levels are about 350 parts per million in the air. Exhaled breath carries about 38,000 parts per million of carbon dioxide. Indoors, he said, if the air has 1,000 parts per million carbon dioxide content or less, "that''s pretty good," Milton said.

弥尔顿说,在建筑物中,二氧化碳监测器可以帮助管理者了解空气是否得到了适当的净化。他说,在城市户外,空气中的二氧化碳含量约为百万分之350。人们呼出的空气中含有大约38,000 ppm的二氧化碳。他说,在室内,如果空气中的二氧化碳含量低于百万分之一千,“那就很好了,”米尔顿说。

What do the other thousands of experts say


Rose dilley
As I suspected some time ago - it sounds like one of the ways TB was transmitted. So, wearing a mask protects you ''and'' others.


Please do not mix science with social egineering. Not your job Geek Squad. Just the facts peer reviewed. Thank you for you contribution which honestly has been minimal. We have national admin MIA and the scientific community needs to step up or what good are you.


Nathan G
Their intention is to inform. Your interpretation is to panic. This further supports the masks to suppress the virus by limiting the amount of particulates released into the air. Wear a mask, stay away from others, avoid large groups, and meet outside. No panic needed.


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