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Masks may not just prevent you from spreading or getting the virus. Now, a growing stack of evidence seems to say that a mask reduce the severity of infection. If so, that could make a mask more powerful than any therapeutic.
How could a mask do that — the proof would have to be strong, to say such a thing, right? Yes.
Dr. Monica Gandhi, an infectious disease specialist and professor of medicine at the University of California at San Francisco, has that evidence in spades.
She offers three categories of evidence:
The CDC estimated as of July 10, 2020, that 40% of infected people had no symptoms. As we’ve learned, the good and the bad of this is that many people don’t fall ill, but the bad part is that they can spread it to those who will fall ill or die.
About 47% of Americans fall into the high-risk group. In fact, we may have one of the highest risk populations on earth because obesity tops the lists for pre-existing conditions that increase the risk of severe Covid in all ages.
Initially, we wondered if the lower death rates in countries like South Korea could have reflected their much more aggressive initial testing. When you find the contacts of people known to have the virus and test them, then you catch more of the mild cases.
Missing mild cases makes it seem like there are more severe cases than reality, but differences in testing don’t appear to explain all of it. The evidence says masks may have gifted us an unexpected benefit.
No matter the mask type, including textile masks, wearing one will filter a majority of viral particles, according to Gandhi. Whether the concern is a virus traveling inward or outward, a mask stands a good chance of stopping the virus.
Tests with animals show that number of viral particles that infect you matters. Think of it as a dose where a high dose has more impact than a low dose. Animals infected with more virus particles got sicker than animals given fewer.
Enter, hamsters. Hamsters appear to be the best stand-in for a human. That no one published a picture of a hamster wearing a mask with their studies may be one of the great injustices of our time — don’t worry. I wrote to them about my grievances.
Gandhi explained that people exposed to a larger “dose” of the virus trigger a much more aggressive response. In these cases, the immune system battles the virus, but the amount of friendly fire goes up with a more aggressive response.
If an immune response becomes too strong, especially if it causes a heart attack or destroys the lungs, it can become fatal. The actual cause of death may vary, but the immune response to the virus still underlies the different causes of death.
Fewer viruses means your body responds much less enthusiastically. That means more mild or no symptoms, but that’s not the best part.
People wearing masks who catch the virus and develop an asymptomatic infection still show immunity, specifically the kind of immunity that Gandhi feels has a good chance of protecting a person, at least until a vaccine materializes.
The Diamond Princess cruise ship, the location of one of the earliest outbreaks in a contained setting, had a high rate of infections with symptoms. Most people who caught the virus felt sick. Only 18% of people were asymptomatic, but no masking took place either.
On an Argentinian cruise ship the story differed. The cruise line gave everyone masks, and then there was an outbreak.
Everyone in the crew and the guests wore the masks. An outbreak study showed that the rate of asymptomatic infection skyrocketed to a shocking 81%.
Next to the 18% asymptomatic cases on the Diamond Princess, that’s stunning.
In Oregon, a seafood processing plant and a chicken processing plant in Arkansas, workers wore masks preemptively.
It’s important to note the outbreaks still happened. This virus is that infectious, but the masks appear to have increased the asymptomatic cases dramatically.
For both locations, 95% of people infected had no symptoms and they developed immunity that should protect them long enough for us to get a vaccine.
This drives home the power of masking. It may be more powerful than distancing.
Another example, comes from an outbreak in Indiana where all patients and staff wore masks. A single symptomatic patient exposed the staff who caught the virus and developed antibodies. The twist is that none of the new infections had any symptoms.
Gandhi said, “I feel confident going out in public with the mask.” Indeed, her research suggests we all should breathe a little easier donning a mask.
The most dramatic example supporting this idea comes from two hairstylists in Missouri. Their employer required they wear masks, and the two tested positive after exposing 140 people together. No one tested positive or reported a symptomatic infection, and one stylist infected people in her personal life.
Still, customers close to her face did not fall ill.
Asian countries that experienced SARS and MER, two of the closest relatives of the virus that causes COVID-19, had partial mask-wearing in their culture already. These included Hong Kong, Singapore, Taiwan, Vietnam, and Thailand, Japan, and parts of China. Many in Asian countries wear masks when they feel unwell out of consideration for others. Masks, not worn for pollution, most often appear on the faces of people who feel sick.
Many of these countries opened society, with universal mask-wearing. Outbreaks still happened. That’s important to note.
The key difference between those countries and the US is the death rate. In the US, the death rate is well above 1% (at least 180 thousand people died and we have at least 2 million recovered cases, or 8.6% of concluded cases ending in death), though the proportion of severe cases is likely somewhat inflated by trends that happened in the early outbreak period.
Perhaps, the single most notable case report detailed a man who flew from China to Toronto. He had a cough, and because he came from a culture where they wear masks when sick to protect others, he wore a mask. All twenty-five people seated close to him tested negative.
Taiwan, a country of 23 million, has had seven deaths in total. Seven.
Taiwan has been open for months, though everyone is still wearing masks. Acceptance wasn’t the case everywhere.
Western societies saw this as an infringement on personal rights —noteworthy: masks were common in 1918 and during the polio outbreaks. Supreme Courts ruled that the state had the power to issue such measures. The founding fathers penned the document in a time of outbreak, so it only makes sense they planned for dealing with them.
Countries outside of Asia like the Czech Republic mandated universal wearing March 23. Everyone followed the mandates. It may have been because most experts believed the economy would tie close to how well a country controlled spread. That is how pandemics and epidemics have panned out in the past.
Very few people died and the case fatality rate there has remained low. The evidence speaks: Masks work. History speaks: the US has employed such measures before yet we had freedom before COVID-19 began. That means that past pandemics and epidemics ended, and with them, mask wearing.
The problem with asymptomatic infection is that you can pass it on if you’re not wearing a mask, but the good thing about it is that people without symptoms are unlikely to spread the virus wearing a mask.
The point of the CDC’s initial recommendations to our country on April 3, to say that we should wear masks out in public was actually to prevent people from giving it to others and not protection.
We know now that it offers some protection to the wearer. That means mask wearing protected you and those around you. The good news doesn’t stop there.
That may be better news than a vaccine because we can do that now. No production fiasco or conundrum to answer. Find one where you are, wear it, and in 2 to 4 months, our country looks like an entirely different place. That’s something on which one can really hang their hope.
Dragging our feet is crushing our economy and mental health. We have the power to end it. We can do it now.
Main References:
1.
Gandhi, M., Beyrer, C. & Goosby, E. Masks Do More Than Protect Others During COVID-19: Reducing the Inoculum of SARS-CoV-2 to Protect the Wearer. J GEN INTERN MED(2020). https://doi.org/10.1007/s11606-020-06067-8
Audio References:
1.
Sharfstein, Joshua, and Monica Gandhi. “Asymptomatic Infection with COVID-19.” Public Health On Call, The Johns Hopkins University, 21 Aug. 2020, johnshopkinssph.libsyn.com/142-asymptomatic-infection-with-covid-19?tdest_id=1899134.
Text References
1.
Centers for Disease Control and Prevention. Regarding the Use of Cloth Face Coverings, Especially in Areas of Significant Community-Based Transmission. April 3, 2020. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover.html. Accessed June 22, 2020
2.
World Health Organization. Advice on the use of masks in the context of COVID-19. Interim guidance. 6 April 2020. Accessible at: https://apps.who.int/iris/handle/10665/331693. Accessed June 22, 2020
3.
World Health Organization. Advice on the use of masks in the context of COVID-19, Interim guidance, 5 June 2020. Accessible at: https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak. Accessed June 22, 2020
4.
Gandhi M, Yokoe DS, Havlir DV. Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19. N Engl J Med2020; 382:2158-2160
5.
He X, Lau EHY, Wu P, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med 2020; 26(5): 672-5.
6.
Stutt R, Retkute R, Bradley M, Gilligan CA, Colvin J. A modelling framework to assess the likely effectiveness of facemasks in combination with ‘lock-down’ in managing the COVID-19 pandemic. Proc R Soc 2020, https://doi.org/10.1098/rspa.2020.0376.
7.
Lyu W, Wehby GL. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US. Health Aff (Millwood) 2020: 101377hlthaff202000818. Accessed June 22, 2020
8.
3 Massachusetts cities to begin issuing fines for people not wearing face masks in public. 7 News Boston. April 29, 2020. Acccessible at: https://whdh.com/news/3-massachusetts-cities-to-begin-issuing-fines-for-people-not-wearing-face-masks-in-public/. Accessed June 22, 2020
9.
Kai D. et al. Universal Masking is Urgent in the COVID-19 Pandemic: SEIR and Agent Based Models, Empirical Validation, Policy Recommendations. April 22, 2020. Accessible at: https://arxiv.org/pdf/2004.13553.pdf. Accessed June 22, 2020
10.
Gandhi M, Havlir D. The Time for Universal Masking of the Public for Coronavirus Disease 2019 Is Now. Open Forum Infect Dis 2020; 7(4): ofaa131.
11.
Eikenberry SE, Mancuso M, Iboi E, et al. To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic. Infect Dis Model 2020; 5: 293-308.
12.
Handel A, Li Y, McKay B, Pawelek KA, Zarnitsyna V, Antia R. Exploring the impact of inoculum dose on host immunity and morbidity to inform model-based vaccine design. PLoS Comput Biol 2018; 14(10): e1006505.
13.
Miller DS, Kok T, Li P. The virus inoculum volume influences outcome of influenza A infection in mice. Lab Anim 2013; 47(1): 74-7.
14.
Raoult D, Zumla A, Locatelli F, Ippolito G, Kroemer G. Coronavirus infections: Epidemiological, clinical and immunological features and hypotheses. Cell Stress 2020; 4(4): 66-75.
15.
Yang R, Gui X, Xiong Y. Comparison of Clinical Characteristics of Patients with Asymptomatic vs Symptomatic Coronavirus Disease 2019 in Wuhan, China, JAMA Netw Open 2020; 3(5): e2010182.
16.
Chan JF, Zhang AJ, Yuan S, et al. Simulation of the clinical and pathological manifestations of Coronavirus Disease 2019 (COVID-19) in golden Syrian hamster model: implications for disease pathogenesis and transmissibility. Clin Infect Dis 2020.
17.
McKenney DG, Kurath G, Wargo AR. Characterization of infectious dose and lethal dose of two strains of infectious hematopoietic necrosis virus (IHNV). Virus Res 2016; 214: 80-9.
18.
Reed LJ, Muench H. A simple method of estimating fifty per cent endpoints. The American Journal of Hygiene. 1938;27(3):493-7.
19.
Casadevall A. The Pathogenic Potential of a Microbe. mSphere 2017; 2(1).
20.
Bouvier NM, Lowen AC. Animal Models for Influenza Virus Pathogenesis and Transmission. Viruses 2010; 2(8): 1530-63.
21.
Tao X, Garron T, Agrawal AS, et al. Characterization and Demonstration of the Value of a Lethal Mouse Model of Middle East Respiratory Syndrome Coronavirus Infection and Disease. J Virol 2016; 90(1): 57-67.
22.
Gralinski LE, Ferris MT, Aylor DL, Whitmore AC, Green R, Frieman MB, et al. Genome Wide Identification of SARS-CoV Susceptibility Loci Using the Collaborative Cross. PLoS Genet. 2015;11(10):e1005504. .
23.
Roberts A, Deming D, Paddock CD, et al. A mouse-adapted SARS-coronavirus causes disease and mortality in BALB/c mice. PLoS Pathog2007; 3(1): e5.
24.
Subbarao K, McAuliffe J, Vogel L, et al. Prior infection and passive transfer of neutralizing antibody prevent replication of severe acute respiratory syndrome coronavirus in the respiratory tract of mice. J Virol2004; 78(7): 3572-7.
25.
Virlogeux V, Fang VJ, Wu JT, et al. Brief Report: Incubation Period Duration and Severity of Clinical Disease Following Severe Acute Respiratory Syndrome Coronavirus Infection. Epidemiology 2015; 26(5): 666-9.
26.
Davis N. Who is most at risk of contracting coronavirus? The Guardian2020 [Last accessed 2020-06-06]; Available from: https://www.theguardian.com/world/2020/feb/21/who-is-most-at-risk-of-contracting-coronavirus. Accessed June 22, 2020
27.
Chan JF, Yuan S, Zhang AJ, et al. Surgical mask partition reduces the risk of non-contact transmission in a golden Syrian hamster model for Coronavirus Disease 2019 (COVID-19). Clin Infect Dis 2020. https://doi.org/10.1093/cid/ciaa644
28.
Smereka J, Ruetzler K, Szarpak L, Filipiak KJ, Jaguszewski M. Role of mask/respirator protection against SARS-CoV-2. Anesth Analg 2020. Accessed June 22, 2020
29.
Engelking HM, Leong JC. The glycoprotein of infectious hematopoietic necrosis virus elicits neutralizing antibody and protective responses. Virus Res 1989; 13(3): 213-30.
30.
S.E. LaPatra, J.L. Fryer, J.S. Rohovec. Virulence comparison of different electropherotypes of infectious hematopoietic necrosis virus. Dis. Aquat. Org., 16 (1993), pp. 115-1.
31.
Kim R, Faisal M. Comparative susceptibility of representative Great Lakes fish species to the North American viral hemorrhagic septicemia virus Sublineage IVb. Dis Aquat Organ 2010; 91(1): 23-34.
32.
Brown JD, Stallknecht DE, Berghaus RD, Swayne DE. Infectious and lethal doses of H5N1 highly pathogenic avian influenza virus for house sparrows (Passer domesticus) and rock pigeons (Columbia livia). J Vet Diagn Invest 2009; 21(4): 437-45.
33.
S.E. LaPatra, J.L. Fryer, J.S. Rohovec. Virulence comparison of different electropherotypes of infectious hematopoietic necrosis virus. Dis. Aquat. Org., 16 (1993), pp. 115-120.
34.
Memoli MJ, Czajkowski L, Reed S, et al. Validation of the wild-type influenza A human challenge model H1N1pdMIST: an A(H1N1)pdm09 dose-finding investigational new drug study. Clin Infect Dis 2015; 60(5): 693-702.
35.
Buitrago-Garcia D et al. The role of asymptomatic SARS-CoV-2 infections: rapid living systematic review and meta-analysis. May 24, 2020. Accessible at: https://doi.org/10.1101/2020.04.25.20079103.this. Accessed June 22, 2020
36.
Oran DP, Topol EJ. Prevalence of Asymptomatic SARS-CoV-2 Infection: A Narrative Review. Ann Intern Med 2020. https://doi.org/10.7326/M20-3012
37.
Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill 2020; 25(10).
38.
Ing AJ, Cocks C, Green JP. COVID-19: in the footsteps of Ernest Shackleton. BMJ Thorax. https://doi.org/10.1136/thoraxjnl-2020-215091.
39.
Hains DS, Schwaderer AL, Carroll AE, et al. Asymptomatic Seroconversion of Immunoglobulins to SARS-CoV-2 in a Pediatric Dialysis Unit. JAMA 2020;323(23):2424-2425
40.
Cline S. Cases at seafood plant cause spike in Oregon COVID numbers. The Associated Press. June 9, 2020. Accessible at: https://www.newsbreak.com/oregon/salem/news/0PI8ZP7b/cases-at-seafood-plant-cause-spike-in-oregon-covid-numbers. Accessed June 22, 2020
41.
124 COVID-19 cases reported at Pacific Seafood in Newport. KGW. June 8, 2020. Newport, Oregon. Accessible at: https://www.kgw.com/article/news/health/coronavirus/pacific-seafood-outbreak-increases-to-124-covid-19-cases/283-ffeb0712-76c0-45ea-b6c8-b7644def0ad1. Accessed June 22, 2020
42.
Hundreds test positive at Tyson Foods plant in Arkansas as China suspends imports. June 22, 2020. Associated Press. https://www.latimes.com/world-nation/story/2020-06-22/hundreds-test-positive-coronavirus-tyson-foods-plant-arkansas.
43.
San Francisco Department of Public Health. Order of the Health Officer of the City and County of San Francisco Generally Requiring Members of the Public and Workers to Wear Face Coverings. April 17, 2020. Accessible at: https://www.sfdph.org/dph/alerts/files/OrderNoC19-12-RequiringFaceCovering-04172020.pdf. Accessed June 22, 2020
44.
Ward A. How masks helped Hong Kong control the coronavirus. Vox. May 18, 2020. Accessible at: https://www.vox.com/2020/5/18/21262273/coronavirus-hong-kong-masks-deaths-new-york. Accessed June 22, 2020
45.
Niemietz B. Photo of 1918 college football fans wearing face masks points to the past and future. New York Daily News. May 25, 2020. Accessible at: https://www.nydailynews.com/coronavirus/ny-photo-mask-georgia-tech-1918-pandemic-flu-coronavirus-20200525-fbkqrf6tqjgf7plck2emfjdjvi-story.html. Accessed June 22, 2020
46.
Czechs get to work making masks after government decree. The Guardian. March 30, 2020. Accessible at: https://www.theguardian.com/world/2020/mar/30/czechs-get-to-work-making-masks-after-government-decree-coronavirus. Accessed June 22, 2020
47.
World Health Organization (WHO) Coronavirus Disease (COVID-19) Dashboard. June 19, 2020 (updated daily). Accessible at: https://covid19.who.int/. Accessed June 22, 2020
48.
Doi A et al. Seroprevalence of novel coronavirus disease (COVID-19) in Kobe, Japan. May 1, 2020. medRxiv preprint https://doi.org/10.1101/2020.04.26.20079822. Accessed June 22, 2020
49.
Leslie M. T cells found in COVID-19 patients ‘bode well’ for long-term immunity. Science. May. 14, 2020. https://www.sciencemag.org/news/2020/05/t-cells-found-covid-19-patients-bode-well-long-term-immunity?utm. Accessed June 22, 2020