Cloth Masks Do Protect the Wearer - Breathing in Less Coronavirus Means You Get Less Sick
By Monica Gandhi
Masks slow the spread of SARS-CoV-2 by reducing how much infected people spray the virus into the environment around them when they cough or talk. Evidence from laboratory experiments, hospitals and whole countries show that masks work, and the Centers for Disease Control and Prevention recommends face coverings for the U.S. public. With all this evidence, mask wearing has become the norm in many places.
I am an infectious disease doctor and a professor of medicine at the University of California, San Francisco. As governments and workplaces began to recommend or mandate mask wearing, my colleagues and I noticed an interesting trend. In places where most people wore masks, those who did get infected seemed dramatically less likely to get severely ill compared to places with less mask-wearing.
It seems people get less sick if they wear a mask.
When you wear a mask – even a cloth mask – you typically are exposed to a lower dose of the coronavirus than if you didn't. Both recent experiments in animal models using coronavirus and nearly a hundred years of viral research show that lower viral doses usually means less severe disease.
No mask is perfect, and wearing one might not prevent you from getting infected. But it might be the difference between a case of COVID-19 that sends you to the hospital and a case so mild you don't even realize you're infected.
Exposure Dose Determines Severity of Disease
When you breathe in a respiratory virus, it immediately begins hijacking any cells it lands near to turn them into virus production machines. The immune system tries to stop this process to halt the spread of the virus.
The amount of virus that you're exposed to – called the viral inoculum, or dose – has a lot to do with how sick you get. If the exposure dose is very high, the immune response can become overwhelmed. Between the virus taking over huge numbers of cells and the immune system's drastic efforts to contain the infection, a lot of damage is done to the body and a person can become very sick.
On the other hand, if the initial dose of the virus is small, the immune system is able to contain the virus with less drastic measures. If this happens, the person experiences fewer symptoms, if any.
This concept of viral dose being related to disease severity has been around for almost a century. Many animal studies have shown that the higher the dose of a virus you give an animal, the more sick it becomes. In 2015, researchers tested this concept in human volunteers using a nonlethal flu virus and found the same result. The higher the flu virus dose given to the volunteers, the sicker they became.
In July, researchers published a paper showing that viral dose was related to disease severity in hamsters exposed to the coronavirus. Hamsters who were given a higher viral dose got more sick than hamsters given a lower dose.
Based on this body of research, it seems very likely that if you are exposed to SARS-CoV-2, the lower the dose, the less sick you will get.
So what can a person do to lower the exposure dose?
Masks Reduce Viral Dose
Most infectious disease researchers and epidemiologists believe that the coronavirus is mostly spread by airborne droplets and, to a lesser extent, tiny aerosols. Research shows that both cloth and surgical masks can block the majority of particles that could contain SARS-CoV-2. While no mask is perfect, the goal is not to block all of the virus, but simply reduce the amount that you might inhale. Almost any mask will successfully block some amount.
Laboratory experiments have shown that good cloth masks and surgical masks could block at least 80% of viral particles from entering your nose and mouth. Those particles and other contaminants will get trapped in the fibers of the mask, so the CDC recommends washing your cloth mask after each use if possible.
The final piece of experimental evidence showing that masks reduce viral dose comes from another hamster experiment. Hamsters were divided into an unmasked group and a masked group by placing surgical mask material over the pipes that brought air into the cages of the masked group. Hamsters infected with the coronavirus were placed in cages next to the masked and unmasked hamsters, and air was pumped from the infected cages into the cages with uninfected hamsters.
As expected, the masked hamsters were less likely to get infected with COVID-19. But when some of the masked hamsters did get infected, they had more mild disease than the unmasked hamsters.
Masks Increase Rate of Asymptomatic Cases
In July, the CDC estimated that around 40% of people infected with SARS-CoV-2 are asymptomatic, and a number of other studies have confirmed this number.
However, in places where everyone wears masks, the rate of asymptomatic infection seems to be much higher. In an outbreak on an Australian cruise ship called the Greg Mortimer in late March, the passengers were all given surgical masks and the staff were given N95 masks after the first case of COVID-19 was identified. Mask usage was apparently very high, and even though 128 of the 217 passengers and staff eventually tested positive for the coronavirus, 81% of the infected people remained asymptomatic.
Further evidence has come from two more recent outbreaks, the first at a seafood processing plant in Oregon and the second at a chicken processing plant in Arkansas. In both places, the workers were provided masks and required to wear them at all times. In the outbreaks from both plants, nearly 95% of infected people were asymptomatic.
There is no doubt that universal mask wearing slows the spread of the coronavirus. My colleagues and I believe that evidence from laboratory experiments, case studies like the cruise ship and food processing plant outbreaks and long-known biological principles make a strong case that masks protect the wearer too.
The goal of any tool to fight this pandemic is to slow the spread of the virus and save lives. Universal masking will do both.
Monica Gandh is a Professor of Medicine, Division of HIV, Infectious Diseases and Global Medicine at the University of California, San Francisco.
Disclosure statement: Monica Gandhi does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Reposted with permission from The Conversation.
By Deborah Moore, Michael Simon and Darryl Knudsen
There's some good news amidst the grim global pandemic: At long last, the world's largest dam removal is finally happening.
A young activist for a free-flowing Salween River. A team of campaigners and lawyers from EarthRights International joined Indigenous Karen communities on the Salween in 2018 to celebrate the International Day of Actions for Rivers on March 14. This year, EarthRights joined communities living in the Eu-Wae-Tta internally displaced persons camp for a celebration in solidarity with those impacted by dam projects on the Salween River. EarthRights International<p>The dam removal project is a sign of the decline of the hydropower industry, whose fortunes have fallen as the <a href="https://www.bbc.com/news/science-environment-46098118" target="_blank" rel="noopener noreferrer">troubling</a> cost-benefit ratio of dams has become clear over the years. The rise of more cost-effective and sustainable energy sources (including wind and solar) has hastened this shift. This is exactly the type of progress envisioned by the <a href="https://www.yumpu.com/en/document/read/17023836/dams-and-development-a-new-framework-for-decision" target="_blank" rel="noopener noreferrer">World Commission on Dams</a> (WCD), a global multi-stakeholder body that was established by the World Bank and International Union for Conservation of Nature in 1998 to investigate the effectiveness and performance of large dams around the world. The WCD released a damning landmark <a href="https://www.un.org/press/en/2000/20001117.dam.pressconferencepm.doc.html" target="_blank" rel="noopener noreferrer">report</a> in November 2000 on the enormous financial, environmental and human costs and the dismal performance of large dams. The commission spent <a href="https://www.un.org/press/en/2000/20001117.dam.pressconferencepm.doc.html" target="_blank" rel="noopener noreferrer">two years</a> analyzing the outcome of the trillions of dollars invested in dams, reviewing dozens of case studies and testimonies from over a thousand communities and individuals, before producing the report.</p><p>But despite this progress, we cannot take hydropower's decline as inevitable. As governments around the world plan for a post-pandemic recovery, hydropower companies sense an opportunity. The industry is eager to recast itself as climate-friendly (<a href="https://www.ecowatch.com/how-green-is-hydropower-1919539525.html" target="_self">it's not</a>) and <a href="https://www.hydropower.org/covid-19" target="_blank">secure</a> precious stimulus funds to revive its dying industry — at the expense of people, the environment and a truly just, green recovery.</p>
Hydropower’s Troubling Record<p>The world's largest hydropower dam removal project on the Klamath River is a significant win for tribal communities. But while the Yurok and Karuk tribes <a href="https://www.karuk.us/images/docs/press/bring_salmon_home.php" target="_blank">suffered</a> terribly from the decline of the Klamath's fisheries, they were by no means alone in that experience. The environmental catastrophe that occurred along the Klamath River has been replicated all over the world since the global boom in hydropower construction <a href="https://www.nationalgeographic.com/environment/article/hydropower" target="_blank">began</a> early in the 20th century.</p><p>The rush to dam rivers has had huge consequences. After decades of rampant construction, only <a href="https://www.nationalgeographic.com/environment/2019/05/worlds-free-flowing-rivers-mapped-hydropower/" target="_blank">37 percent of the world's rivers remain free-flowing</a>, according to <a href="https://www.nature.com/articles/s41586-019-1111-9" target="_blank" rel="noopener noreferrer">one study</a>. River fragmentation has <a href="https://academic.oup.com/bioscience/article/70/4/330/5732594" target="_blank" rel="noopener noreferrer">decimated freshwater habitats and fish stocks</a>, threatening food security for millions of the world's most vulnerable people, and hastening the <a href="https://www.forbes.com/sites/jeffopperman/2020/10/13/freshwater-wildlife-continues-to-decline-but-new-energy-trendlines-suggest-we-can-bend-that-curve/?sh=f9d175a61ee4" target="_blank" rel="noopener noreferrer">decline of other myriad freshwater species</a>, including mammals, birds and reptiles.</p><p>The communities that experienced the most harm from dams — whether in Asia, Latin America or Africa — often lacked political power and access. But that didn't stop grassroots movements from organizing and growing to fight for their rights and livelihoods. The people affected by dams began raising their voices, sharing their experiences and forging alliances across borders. By the 1990s, the public <a href="https://tinyurl.com/y55lnlst" target="_blank" rel="noopener noreferrer">outcry</a> against large dams had grown so loud that it finally led to the establishment of the WCD.</p><p>What the WCD found was stunning. While large dam projects had brought some economic benefits, they had also <a href="https://www.irn.org/wcd/" target="_blank" rel="noopener noreferrer">forcibly displaced an estimated 40 to 80 million people in the 20th century alone</a>. To put that number into perspective, it is more than the current population of present-day <a href="https://data.worldbank.org/indicator/SP.POP.TOTL?locations=FR" target="_blank" rel="noopener noreferrer">France</a> or the <a href="https://data.worldbank.org/indicator/SP.POP.TOTL?locations=GB" target="_blank" rel="noopener noreferrer">United Kingdom</a>. These people lost their lands and homes to dams, and often with no compensation.</p><p>Subsequent research has compounded that finding. A paper published in <a href="https://tinyurl.com/c7uznz" target="_blank" rel="noopener noreferrer">Water Alternatives</a> revealed that globally, more than <a href="https://tinyurl.com/yxw8x7ab" target="_blank" rel="noopener noreferrer">470 million people living downstream from large dams</a> have faced significant impacts to their lives and livelihoods — much of it due to disruptions in water supply, which in turn harm the complex web of life that depends on healthy, free-flowing rivers. The WCD's findings, released in 2000, <a href="https://www.irn.org/wcd/" target="_blank" rel="noopener noreferrer">identified</a> the importance of restoring rivers, compensating communities for their losses, and finding better energy alternatives to save rivers and ecosystems.</p>
Facing a New Crisis<p>Twenty years after the WCD uncovered a crisis along the world's rivers and recommended a new development path — one that advances community-driven development and protects freshwater resources — we find ourselves in the midst of another crisis. The global pandemic has hit us hard, with surging loss of life, unemployment and instability.</p><p>But as governments work to rebuild economies and create job opportunities in the coming years, we have a choice: Double down on the failed, outdated technologies that have harmed so many, or change course and use this transformative moment to rebuild our natural systems and uplift communities.</p><p>There are many reasons to fight for a green recovery. The climate is changing even <a href="https://www.nature.com/articles/d41586-018-07586-5" target="_blank" rel="noopener noreferrer">faster</a> than expected, and some dams — especially those with reservoirs in hot climates — <a href="https://tinyurl.com/w6w29t8" target="_blank" rel="noopener noreferrer">have been found to emit more greenhouse gases than a fossil fuel power plant</a>. Other estimates have put global reservoirs' human-made greenhouse gas emissions each year on par with <a href="https://www.climatecentral.org/news/greenhouse-gases-reservoirs-fuel-climate-change-20745" target="_blank" rel="noopener noreferrer">Canada's</a> total emissions.</p><p>Meanwhile, we now understand that healthy rivers and freshwater ecosystems play a <a href="https://www.environment.gov.au/system/files/resources/b55b1fe4-7d09-47af-96c4-6cbb5f106d4f/files/wetlands-role-carbon-cycle.pdf" target="_blank" rel="noopener noreferrer">critical role in regulating and storing carbon</a>. And at a time when <a href="https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/" target="_blank" rel="noopener noreferrer">biodiversity loss is soaring</a>, anything we can do to <a href="https://academic.oup.com/bioscience/article/70/4/330/5732594" target="_blank" rel="noopener noreferrer">restore habitat is key</a>. But with <a href="https://www.researchgate.net/publication/271996520_A_Global_Boom_in_Hydropower_dam_Construction" target="_blank" rel="noopener noreferrer">more than 3,700 major dams proposed or under construction</a> in the world (primarily in the Global South, with over <a href="https://news.mongabay.com/2020/08/more-than-500-dams-planned-inside-protected-areas-study/" target="_blank" rel="noopener noreferrer">500 of these in protected areas</a>), according to a 2014 report — and the hydropower industry <a href="https://www.hydropower.org/covid-19" target="_blank" rel="noopener noreferrer">jockeying</a> for scarce stimulus dollars — we must act urgently.</p>
Signs of Hope<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTcxMzUyMS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxOTcyNTc3OX0.EbqBVPs2kjhrY5AqnZXOb_GX-s6pw4qyJmmeISzKA6U/img.png?width=980" id="a81d0" class="rm-shortcode" data-rm-shortcode-id="87bc79d69f72e9334a78da8e0355e6ae" data-rm-shortcode-name="rebelmouse-image" data-width="1620" data-height="1068" />
Fish catch at the Siphandone on the Mekong River, prior to the completion of the Don Sahong Dam. Pai Deetes / International Rivers<p>So what would a strong, resilient and equitable recovery look like in the 21st century? Let's consider one example in Southeast Asia.</p><p>Running through six countries, the Mekong River is the world's 12th-longest river, which is home to one of the world's most biodiverse regions, and includes the world's <a href="https://www.worldwildlife.org/places/greater-mekong#" target="_blank" rel="noopener noreferrer">largest</a> inland fishery. Around <a href="https://tinyurl.com/y6jrarjo" target="_blank" rel="noopener noreferrer">80 percent of the nearly 65 million people</a> who live in the Lower Mekong River Basin depend on the river for their livelihoods, according to the Mekong River Commission. In 1994, Thailand built the Pak Mun Dam on a Mekong tributary. <a href="https://tinyurl.com/y5ekfp4h" target="_blank" rel="noopener noreferrer">Six years later</a>, the <a href="https://tinyurl.com/yxcvs6up" target="_blank" rel="noopener noreferrer">WCD studied the dam's performance</a> and submitted its conclusions and recommendations as part of its final report in 2000. According to the WCD report, the Pak Mun Dam did not deliver the peaking energy service it was designed for, and it <a href="https://tinyurl.com/y38p3jaw" target="_blank" rel="noopener noreferrer">physically blocked a critical migration route</a> for a range of fish species that migrated annually to breeding grounds upstream in the Mun River Basin. Cut off from their customary habitat, fish stocks plummeted, and so did the livelihoods of the local people.</p><p>Neighboring Laos, instead of learning from this debacle, followed in Thailand's footsteps, <a href="https://tinyurl.com/y4eaxcq2" target="_blank" rel="noopener noreferrer">constructing two dams on the river's mainstem</a>, Xayaburi Dam, commissioned in 2019, and Don Sahong Dam, commissioned in 2020. But then a sign of hope appeared. In early 2020, just as the pandemic began to spread across the world, the <a href="https://www.theguardian.com/world/2020/mar/20/cambodia-scraps-plans-for-mekong-hydropower-dams" target="_blank" rel="noopener noreferrer">Cambodian government reconsidered its plans to build more dams on the Mekong</a>. The science was indisputable: A government-commissioned report showed that further dams would <a href="https://www.theguardian.com/environment/2018/may/16/leaked-report-warns-cambodias-biggest-dam-could-literally-kill-mekong-river" target="_blank" rel="noopener noreferrer">reduce the river's wild fisheries, threaten critically endangered Irrawaddy dolphins</a> and <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013WR014651" target="_blank" rel="noopener noreferrer">block nutrient-rich sediment from the delta's fertile agricultural lands</a>.</p><p><a href="https://data.opendevelopmentmekong.net/dataset/4f1bb5fd-a564-4d37-878b-c288af460143/resource/5f6fe360-7a68-480d-9ba4-12d7b8b805c9/download/volume-3_solar-alternative-to-sambor-dam.pdf" target="_blank" rel="noopener noreferrer">Studies</a> show that Cambodia didn't need to seek billions of dollars in loans to build more hydropower; instead, it could pursue more cost-effective solar and wind projects that would deliver needed electricity at a fraction of the cost — and <a href="https://www.worldwildlife.org/press-releases/wwf-statement-on-cambodian-government-s-decision-to-suspend-hydropower-dam-development-on-the-mekong-river" target="_blank">without the ecological disasters to fisheries and the verdant Mekong delta</a>. And, in a stunning reversal, Cambodia listened to the science — and to the people — and <a href="https://www.theguardian.com/world/2020/mar/20/cambodia-scraps-plans-for-mekong-hydropower-dams" target="_blank">announced</a> a 10-year moratorium on mainstream dams. Cambodia is now <a href="https://www.voanews.com/east-asia-pacific/cambodia-halts-hydropower-construction-mekong-river-until-2030" target="_blank">reconsidering</a> its energy mix, recognizing that mainstream hydropower dams are too costly and undermine the economic and cultural values of its flagship river.</p>
Toward a Green Recovery<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTcxMzUwOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MTMwMjk0M30.0LZCOEVzgtgjm2_7CwcbFfuZlrtUr80DiRYxqKGaKIg/img.jpg?width=980" id="87fe9" class="rm-shortcode" data-rm-shortcode-id="e6b9bfeb013516f6ad5033bb9e03c5ec" data-rm-shortcode-name="rebelmouse-image" data-width="2100" data-height="3086" />
Klamath River Rapids. Tupper Ansel Blake / U.S. Fish and Wildlife Service<p>Increasingly, governments, civil servants and the public at large are rethinking how we produce energy and are seeking to preserve and restore precious freshwater resources. Dam removals are increasing exponentially across <a href="https://www.americanrivers.org/wp-content/uploads/2020/02/DamsRemoved_1999-2019.pdf" target="_blank">North America</a> and <a href="https://damremoval.eu/wp-content/uploads/2019/03/DRE-policy-Report-2018-digitaal-010319.pdf" target="_blank">Europe</a>, and movements advancing <a href="https://www.rightsofrivers.org/" target="_blank">permanent river protection are growing across Latin America, Asia and Africa</a>.</p><p>We must use the COVID-19 crisis to accelerate the trend. Rather than relying on old destructive technologies and industry claims of newfound "<a href="https://www.hydrosustainability.org/news/2020/11/12/consultation-on-a-groundbreaking-global-sustainability-standard-for-hydropower" target="_blank">sustainable hydropower</a>," the world requires a new paradigm for an economic recovery that is rooted both in climate and economic justice as well as river stewardship. Since December 2020, hundreds of groups and individuals from more than 80 countries have joined the <a href="https://www.rivers4recovery.org/" target="_blank" rel="noopener noreferrer">Rivers4Recovery</a> call for a better way forward for rivers and natural places. This paradigm will protect our rivers as critical lifelines — supporting fisheries, biodiversity, water supply, food production, Indigenous peoples and diverse populations around the world — rather than damming and polluting them.</p><p>The promise of the Klamath dam removals is one of restoration — a move that finally recognizes the immense value of free-flowing rivers and the key role they play in <a href="https://f.hubspotusercontent20.net/hubfs/4783129/LPR/PDFs/Living_Planet_Report_Freshwater_Deepdive.pdf" target="_blank" rel="noopener noreferrer">nourishing both the world's biodiversity and hundreds of millions of people</a>. Healthy rivers — connected to watershed forests, floodplains, wetlands and deltas — are key partners in building resilience in the face of an accelerating climate crisis. But if we allow the hydropower industry to succeed in its <a href="https://www.world-energy.org/article/12361.html" target="_blank" rel="noopener noreferrer">cynical grab for stimulus funds</a>, we'll only perpetuate the 20th century's legacy of suffering and environmental degradation.</p><p>We must put our money where our values are. Twenty years ago, the WCD pointed the way forward to a model of development that takes humans, wildlife and the environment into account, and in 2020, we saw that vision flower along the Klamath River. It's time to bring that promise of healing and restoration to more of the world's rivers.</p><p><em>Deborah Moore is a former commissioner of the <a href="https://www.water-alternatives.org/index.php/alldoc/articles/vol3/v3issue2/79-a3-2-2/file" target="_blank" rel="noopener noreferrer" style="">World Commission on Dams</a>. Michael Simon was a member of the <a href="https://www.hydrosustainability.org/assessment-protocol" target="_blank" rel="noopener noreferrer" style="">Hydropower Sustainability Assessment Forum</a>. Darryl Knudsen is the executive director of <a href="https://www.internationalrivers.org" target="_blank" rel="noopener noreferrer" style="">International Rivers</a>.</em></p><p><em>This article first appeared on <a href="https://truthout.org/articles/damming-rivers-is-terrible-for-human-rights-ecosystems-and-food-security/" target="_blank" rel="noopener noreferrer">Truthout</a> and was produced in partnership with <a href="https://independentmediainstitute.org/earth-food-life/" target="_blank" rel="noopener noreferrer">Earth | Food | Life</a>, a project of the Independent Media Institute.</em></p>
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