面具已经成为冠状病毒流行病——起初对美国人来说基本上是陌生的，然后被寻求保护的官员怀疑地对待健康工人，然后被绝望地想要阻止病毒在东北城市的势不可挡的浪潮的公众拥抱。
从那以后，他们成了政治热点，的来源蔑视和混乱一直以来，关于穿什么样的衣服以及它们的有效性的争论都很激烈。
在20世纪早期COVID-19大流行根据当时最好的证据，疾病控制和预防中心(CDC)和其他政府官员劝阻美国人戴口罩，称他们不太可能帮助阻止病毒的传播。
但是随着证据的积累，疾病预防控制中心在4月3日突然改变了方向，鼓励所有美国人戴上面罩来减缓病毒的传播，人们普遍认为病毒是通过呼吸道飞沫传播的。
与此同时，在世界各地，科学家们正疯狂地整理资源，建立一系列广泛的研究来检验这个问题。一些人在他们的实验室里搭建假人，用喷雾罐模拟咳嗽或打喷嚏，并捕捉这些水滴能够飞的距离。
2020年6月30日，副总统彭斯在马里兰州罗克维尔的美国公共卫生服务委任团总部演讲时，摘下了他的面具。
其他人开始了大规模的人口规模的研究，拼命试图辨别掩盖政策是否有可能阻止病毒在社区内的传播。
到6月份，世界卫生组织(世卫组织)加入进来，同意疾病预防控制中心的意见，即人们应该戴口罩——尤其是当其他预防措施，如站在离其他人6英尺远的地方是不可能的时候。
现在，这场全球大流行已经过去了六个多月，专家们表示，已经积累了足够的证据，可以得出结论，口罩对于减缓COVID-19的传播至关重要。
“这是一种简单、廉价的措施，可以对减少病毒的传播产生重大影响，”马萨诸塞州南岸卫生的传染病医生西蒙·怀尔德博士说。“我们必须记住，如果我们不采取这些措施，将会有更多的病例和更多的死亡。”
但是什么样的面具最好呢?专家们一致认为，大多数人不应该使用能保护佩戴者和其他人免受病毒颗粒侵害的N-95口罩，这种口罩仍然供不应求，应该留给医务人员。他们承认面具不是唯一的解决办法。他们说，尽可能与他人保持至少6英尺的距离，经常洗手是阻止COVID-19传播的其他重要方法。
约翰·霍普金斯健康安全中心的高级学者阿梅什·阿达利亚博士说:“口罩不能治愈COVID-19。“这是一种简单的干预措施，可以用来减缓冠状病毒的传播。
为什么面具可能有助于他人
越来越多的科学证据表明戴口罩或自制面膜有两个潜在的好处。首先，如果你是被感染的人，它可能会阻止你将呼吸道飞沫传播给他人。其次，它可能会阻止一些病毒颗粒进入你的嘴和鼻子——这一点对于科学家和公共卫生官员来说更加模糊。
根据今年6月发表在《内科年报》上的一篇评论，随着我们对“沉默传播者”现象的理解，第一个潜在的好处已经变得不可忽视，一些研究估计，超过40%的人可能是病毒携带者，但他们并不知道也没有感觉到任何症状。
“有许多人有轻微的症状，甚至不知道他们被感染了，这可能是病毒的传播。怀尔德说:“面部遮盖有助于防止这种情况发生。
疾病预防控制中心已经介入了这个话题，称现有的科学支持这样的观点，即如果你被感染了，口罩可以帮助保护你周围的人。现在，尽管研究仍在进行中，该机构并没有说口罩本身一定能保护你免受感染。
我们掌握的关于口罩的大部分好数据都是在医疗保健环境中观察到的，比如医院和诊所。最强有力的研究之一来自科学杂志《柳叶刀》(The Lancet)，今年6月，该杂志汇集了来自医疗保健和社区机构的多项研究，发现戴口罩可能会将冠状病毒传播的风险从17%提高到3%。
《自然医学》4月份的一项研究表明，口罩可以减少呼出气体中的雾滴或气溶胶中的季节性冠状病毒和其他呼吸道病毒颗粒的数量，但它没有直接研究COVID-19患者。《卫生事务杂志》6月的另一项研究发现，在强制戴口罩的地方，感染率降低了2%，尽管其他因素也可能导致这一差异。
多项研究发现，面膜越厚越好。与覆盖鼻子和嘴巴的多层口罩(理想情况下为12-16层)相比，薄而宽松的口罩不太可能保护你周围的人。
2020年6月16日，明尼苏达州布鲁明顿，一名戴着口罩的购物者走过美国购物中心
以及他们为什么会帮助你
虽然不太确定，但越来越多的证据表明，面具也可能保护你这个佩戴者。这一理论基于这样一种想法，即虽然口罩可能无法防止你通过口罩的缝隙吸入细小的病毒颗粒，但与你根本不戴口罩相比，它可能会防止你吸入大量的病毒颗粒。
哈佛医学院教授、美国广播公司新闻撰稿人约翰·布朗斯坦说:“尽管没有给予绝对的保护，但戴口罩确实给佩戴者提供了某种程度的保护，这应该会加强那些不愿意采取利他主义公共健康方法的人的力量。”。
专家认为吸入一点点病毒比吸入大量病毒要好，因为较低的病毒载量可能意味着你不太可能得重病。
UCSF-格莱斯顿艾滋病研究中心(CFAR)主任莫尼卡·甘地博士说:“这一理论实际上是基于几乎所有病毒的证据，无论是通过呼吸器、肠胃道、性传播，如果你感染了大量无害的病毒，你会得更多的病。”。
“如果你少吃一剂，你的病就会少一些。如果你使用口罩，你得到的剂量会更少，”甘地说。“我真的相信人口掩蔽会导致更轻微的疾病。这是戴口罩的最大理由。”
即使支持使用口罩的证据不断积累，随着流行病的持续，许多美国人已经厌倦了戴口罩。其他人仍然对面具政策持怀疑态度，因为政府早期的信息是面具没有用。
“我们必须对我们的假设保持谦虚，”疾病预防控制中心首席副主任安妮·舒查特博士在周一的在线问答中说。“不是我们错了，然后我们改变了主意，而是我们不断学习。”
现有的科学数据告诉我们，面具可能会拯救生命。医生说至少它们不会受伤。
怀尔德说:“我能理解有些人对需要一直戴着面具感到沮丧。“但在美国有超过250万病例、超过127，000人死亡且尚未治愈或接种疫苗的大流行期间，我们必须采取一切可能的措施来减缓病毒的传播。”
医学博士阿约德拉·阿迪根是儿科和成人精神病学的主治医师，也是耶鲁大学儿童和青少年精神病学的前研究员。亚历克西斯·卡灵顿医学博士目前正在纽约市埃尔赫斯特医院完成她的内科预科班。斯蒂芬妮·法伯，医学博士，是宾夕法尼亚州匹兹堡的整形外科医生。杰西卡·约翰逊，医学博士，斯坦福大学急诊医学高级住院医师。索尼·萨尔兹曼是美国广播公司新闻医疗组的协调制作人。
Masks are a flashpoint amid the coronavirus pandemic. Here's what science says about them.
Masks have become a symbol of thecoronaviruspandemic -- at first largely foreign to Americans, then treated skeptically by officials looking to preserve protection forhealthworkers and then embraced by a public desperate to stem the overwhelming tide of the virus in northeastern cities.
Since then, they have become apolitical flashpoint,a source ofdefianceandconfusion, all while a debate raged about what type to wear and their effectiveness.
Early in theCOVID-19 pandemic, the Centers for Disease Control and Prevention (CDC) and other government officials discouraged Americans from wearing masks, saying they were unlikely to help stop the spread of the virus, according to the best evidence at the time.
But as evidence accumulated, the CDC made an abrupt about-face on April 3, encouraging all Americans to don face coverings to slow transmission of the virus, which was largely believed to be spread through respiratory droplets.
Meanwhile, across the world, scientists were frantically marshaling resources to set up a wide range of studies to examine the issue. Some set up dummies in their laboratories, mimicking coughing or sneezing using spray canisters and capturing the distance these droplets were able to fly.
Vice President Pence removes his mask as he arrives at the podium to speak to the Commissioned Corps of the U.S. Public Health Service at their headquarters in Rockville, Md., June 30, 2020.
Others embarked on massive population-scale studies, trying desperately to discern whether masking policies were likely to stop the spread of the virus within communities.
By June, the World Health Organization (WHO) weighed in, agreeing with the CDC that people should wear masks -- especially when other preventative measures, like standing 6 feet away from other people -- are not possible.
Now, more than six months into this global pandemic, experts say enough evidence has been amassed to conclude that masks are critical in mitigating COVID-19 spread.
“It is a simple, inexpensive measure that can have a significant impact in reducing the spread of the virus, ” said Dr. Simone Wildes, an infectious disease physician at South Shore Health in Massachusetts. “We have to remember if we don't take these measures there will be more cases and more deaths.”
But what kind of mask is best? Experts agree that most people should not be using N-95 masks, which protect both the wearer and others from viral particles, are still in short supply and should be reserved for medical professionals. And they acknowledge that masks are not the only solution. Staying at least 6 feet away from other people when possible and washing your hands frequently are other important ways of stopping the spread of COVID-19, they said.
“The masks are not a cure for COVID-19,” said Dr. Amesh Adalja, senior scholar at Johns Hopkins Center for Health Security. “It is a simple intervention that can be used to slow the spread of the coronavirus.
Why masks probably help others
Accumulating scientific evidence points to two potential benefits of wearing a mask or homemade face covering. First, it might prevent you from spreading respiratory droplets to others if you are the one who is infected. Second, it might prevent some of the viral particles from getting into your mouth and nose -- a point that has been much murkier from scientists and public health officials.
This first potential benefit has become impossible to ignore as we have come to understand the phenomenon of “silent spreaders,” with some studies estimating that more than 40% of people may be carriers of the virus without knowing it or feeling any symptoms, according to a review published in Annals of Internal Medicine this June.
“There are many people that are out there that have mild symptoms that may not even know they are infected that may be spreading the virus. A facial covering can help prevent that from happening,” said Wildes.
The CDC has weighed in on this topic, saying that existing science supports the idea that masks can help protect the people around you, should you be infected. Right now, the agency stops short of saying that the mask itself can definitely protect you from getting infected, although research is ongoing.
Most of the good data we have on masks has looked at their effectiveness in health care settings, like hospitals and clinics. One of the strongest studies comes from the scientific journal The Lancet this June, which compiled multiple studies from both healthcare and community settings to find that wearing a mask may bring the risk of transmission of coronaviruses from 17% to 3%.
A study in Nature Medicine in April showed that masks reduce the amount of seasonal coronavirus as well as other respiratory viral particles in droplets or aerosols from exhaled breaths, however it did not study patients with COVID-19 directly. Another study in the Journal of Health Affairs in June, found that infection was 2% lower in places where mask mandates were enforced, though other factors could have contributed to this difference.
And multiple studies have found that the thicker the mask, the better. A thin, loose-fitting mask is less likely to protect the people around you compared to a multilayer mask (ideally 12-16 layers) that covers your nose and your mouth.
A shopper wearing a face mask walks through the Mall of America on June 16, 2020 in Bloomington, Minn.
And why they may help you
While less conclusive, growing evidence suggests masks might also protect you, the wearer. This theory relies on the idea that while a mask might not protect you from inhaling small particles of virus through the gaps in the mask, it is likely to prevent you from inhaling massive quantities of viral particles, compared to if you were wearing no mask at all.
“Though not conferring absolute protection, wearing a mask is does provide the wearer some level of protection which should provide reinforcement for those that aren’t willing to take an altruistic public health approach” said John Brownstein, a Harvard Medical School professor and ABC News contributor.
And experts think that inhaling a little bit of virus is better than inhaling a lot of virus, because a lower viral load could mean you’re less likely to get seriously sick.
“This theory is really based on evidence that we have from almost every virus, whether it’s spread in a respirator way, gastrointestinally, sexually, that if you get a large innocuous of virus, you get more ill,” said Dr. Monica Gandhi, director of UCSF-Gladstone Center for AIDS Research (CFAR).
“If you get less of a dose, you get less sick. And if you use masks you get less of a dose,” Gandhi said. “I really do believe that population masking will lead to more mild disease. It’s the biggest argument to [wear a] mask.”
Even as evidence supporting mask use continues to accumulate, many Americans have become weary of wearing them as the pandemic drags on. Others remain skeptical of mask policies because of the government’s early messaging that masks wouldn’t help.
“We have to be humble about our assumptions,” said Dr. Anne Schuchat, principal deputy director of the CDC, during an online Q&A on Monday. “It’s not that we were wrong and then we changed our mind, it’s that we keep learning.”
Existing scientific data tells us it’s likely masks could save lives. And doctors say at the very least, they don’t hurt.
“I can understand the frustration some individuals are experiencing about the need to wear the mask at all times,” said Wildes. “But in the midst of a pandemic with more than 2.5 million cases in the US and more than 127,000 deaths with no cure or vaccine yet, we have to take all measures we can to slow the spread of the virus.”
Ayodola Adigun, M.D., M.S., is an attending in pediatric and adult psychiatry and a former fellow in child and adolescent psychiatry at Yale University. Alexis E. Carrington, M.D. is currently completing her internal medicine preliminary year at Elmhurst Hospital in New York City. Stephanie Farber, M.D. is a plastic surgeon from Pittsburgh, PA. Jessica Johnson, M.D. is a senior resident in emergency medicine at Stanford University. Sony Salzman is coordinating producer of the ABC News Medical Unit.
