Masks are one layer of protection in the multiple layers public health officials use to protect us. Masks work to mitigate transmission and risk of infection.
Meta-analysis: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext
Meta-analysis: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253999/
Mask efficacy for COVID-19. “A conclusion can be reached based on the current studies: correctly wearing masks of all kinds, despite their different designs, functions and effectiveness, will to a large degree reduce the overall risks of COVID‐19 infection and enhance general protection from coronavirus.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7883189/
Effectiveness of Mask Wearing to Control Community Spread
https://jamanetwork.com/journals/jama/fullarticle/2776536
Non-pharmaceutical interventions (hand hygiene and masks) are important to controlling pandemics.
Influenza RCTs:
https://pubmed.ncbi.nlm.nih.gov/19652172/
https://pubmed.ncbi.nlm.nih.gov/22280120/
Masks do not increase CO2 retention
https://uihc.org/health-topics/do-face-masks-make-you-retain-carbon-dioxide
Masks do not cause healthcare problems. “There is virtually no circumstance that warrants an exemption from wearing a mask based on lung disease.”
https://health.clevelandclinic.org/can-face-masks-cause-health-problems/
AAP on masks and speech delays. “There are no known studies that use of a face mask negatively impacts a child’s speech and language development. And consider this: visually impaired children develop speech and language skills at the same rate as their peers. In fact, when one sense is taken away, the others may be heightened. Young children will use other clues provided to them to understand and learn language. They will watch gestures, hear changes in tone of voice, see eyes convey emotions, and listen to words.
https://www.healthychildren.org/English/health-issues/conditions/COVID-19/Pages/Do-face-masks-interfere-with-language-development.aspx
Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools
https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7021e1-H.pdf
COVID-19 Mitigation Practices and COVID-19 Rates in Schools: Report on Data from Florida, New York and Massachusetts (this paper shows decreased staff infections, not significant for student)
https://www.medrxiv.org/content/10.1101/2021.05.19.21257467v1.full.pdf
Minimal transmission of SARS-CoV-2 from paediatric COVID-19 cases in primary schools, Norway, August to November 2020 (minimal transmission where masks not recommended, robust contact tracing/quarantine system)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7791599/
Expert Medical Society Statements in favor of Masking:
Infectious Diseases Society of America (IDSA). https://www.idsociety.org/covid-19-real-time-learning-network/infection-prevention/masks-and-face-coverings-for-the-public/
American Medical Association (AMA). https://www.ama-assn.org/delivering-care/public-health/6-things-doctors-wish-patients-knew-about-masks
American College of Phycisians (ACP) https://www.acponline.org/acp-newsroom/new-policy-supports-wearing-of-masks-to-reduce-transmission-of-covid-19
American Academy of Pediatricians (AAP). https://services.aap.org/en/pages/2019-novel-coronavirus-covid-19-infections/clinical-guidance/cloth-face-coverings/
AAP on masking during sports: https://www.aappublications.org/news/2020/12/04/sportsguidance120420
American Academy of Family Physicians (AAFP). https://familydoctor.org/covid-19-face-masks/
Association of American Medical Colleges (AAMC). https://www.aamc.org/news-insights/press-releases/aamc-releases-national-guidance-face-coverings
Scientific Papers Supporting Mask-Wearing and Mandates, listed in reverse chronological order
2019 A randomised clinical trial to evaluate the safety, fit, comfort of a novel N95 mask in children. 106 age 7-14 used an N95 at rest and on a treadmill monitoring cardioresp parameters. Found to be Comfortable and safe https://pubmed.ncbi.nlm.nih.gov/31831801/
February 5, 2021. Decline in COVID-19 Hospitalization Growth Rates Associated with Statewide Mask Mandates — 10 States, March–October 2020. Statistically significant decline in hospitalization rates of 5-6% per week after a mask mandate after controlling for other measures. . https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7006e2-H.pdf Heesoo Joo, PhD1; Gabrielle F. Miller, PhD1; Gregory Sunshine, JD1; Maxim Gakh, JD2; Jamison Pike, PhD1; Fiona P. Havers, MD1;
February 2. 2021. Hydrating the Respiratory Tract: An Alternative Explanation Why Masks Lower Severity of COVID-19. Biophysical Journal, 2021. https://www.cell.com/biophysj/fulltext/S0006-3495(21)00116-8?rss=yes
January 7, 2021 ”SARS-CoV-2 Transmission From People Without COVID-19 Symptoms” 59% of transmissions of sarscov2 are perpetrated by asymptomatic individuals. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707
November 27, 2020. MMWR Update. “Trends in County-Level COVID-19 Incidence in Counties With and Without a Mask Mandate — Kansas, June 1–August 23, 2020“. https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6947e2-H.pdf
November 23, 2020.”Impact of Masks on Economic Activity”. economy.= locations with a mask mandate had increase consumer movement and spending. Surveys showed a 50% increase in willingness to shop if all shoppers were masked. https://s3-us-west-2.amazonaws.com/marriner-wpmedia/wp-content/uploads/2020/11/Mask-Research_2pager-Nov20_Final.pdf
November 10, 2020 Vanderbilt. “ Tennessee COVID-19 Death Trends Are Lower in Areas with Virus Mitigation Strategies in Place” mandate = death rates decline at a reliable point afford mask mandate initiation across several Tennessee counties. https://www.vumc.org/health-policy/sites/default/files/public_files/Vanderbilt%20COVID%20Report-Masks%20and%20Deaths_Nov10.pdf
July 14, 2020, “Association Between Universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers”. = 9850 hcw with linear decline in infection rates after implementation of universal masking of hcw and patients in the hospital. Independent practice and trend compared to the community. https://jamanetwork.com/journals/jama/fullarticle/2768533
“Visualizing the effectiveness of face masks in obstructing respiratory jets,” Verma et al., June 30 2020, Phys Fluids = respiratory jets were shortened to 2.5 inches by a double layer stitched cotton mask, compared to 8 inches with a commercial cone mask. Uncovered respiratory jet was 8 feet https://aip.scitation.org/doi/pdf/10.1063/5.0016018
June 29, 2020 (non peer reviewed data analysis by Goldman Sachs). “Face Masks and GDP” (financial journal) economy & mandate a national mask mandate could improve the GDP by several percentage points based on estimations https://www.goldmansachs.com/insights/pages/face-masks-and-gdp.html
“Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US” Lyu et al., June 16 2020, Health Affairs = significant decline in daily COVID-19 growth rate after the mandating of face covers in public, while ‘employee only’ mask mandates were not successful. https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818
“Association of country-wide coronavirus mortality with demographics, testing, lockdowns, and public wearing of masks” Leffler et al., June 15 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.05.22.20109231v3
“Identifying airborne transmission as the dominant route for the spread of COVID-19” Zhang et al., June 11 2020, PNAS: https://www.pnas.org/content/117/26/14857
“A modelling framework to assess the likely effectiveness of facemasks in combination with ‘lock-down’ in managing the COVID-19 pandemic” Stutt et al., June 10 2020, Proc. R. Soc. A.: https://royalsocietypublishing.org/doi/10.1098/rspa.2020.0376
META: “Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis,” June 1 2020, Lancet: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext
“Face coverings for the public: Laying straw men to rest” Greenhalgh, May 26 2020, Journal of Evaluation of Clinical Practice = expert opinion piece/ retort to common erroneous assumptions regarding mask logic / reasoning as well as a brief description of the types of evidence we have supporting mask effectiveness and safety. https://onlinelibrary.wiley.com/doi/full/10.1111/jep.13415
“COVID-19 and the Social Distancing Paradox: dangers and solutions” Marchiori, May 26 2020, arXiv = using sensors to detect how close people would approach, a statistically significant increase in social distancing was seen when the belt wearer was masked compared to unmasked. Masking independently increases other social distancing practices. https://arxiv.org/pdf/2005.12446.pdf
“Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Clase et al., May 22 2020, An of Int Med. summary and rebuttal of recently quoted study’s, “tea towel fabric, studied with aerosol-sized particles, filtration efficiency in experiments using a bacterial marker was 83% with 1 layer and 97% with 2 layers, compared with 96% for a medical mask” Cloth can block droplets and aerosols, and layers add efficiency https://www.acpjournals.org/doi/10.7326/M20-2567
“Quantitative Method for Comparative Assessment of Particle Filtration Efficiency of Fabric Masks as Alternatives to Standard Surgical Masks for PPE” Mueller et al., May 18 2020, medRxiv = mean filtration measured across many different type of cloth masks compared to n95. Shows that with increasing fabric layers and focus on fit, filtration can approach the level of an n95 https://www.medrxiv.org/content/10.1101/2020.04.17.20069567v4.full.pdf
“Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China” Wang et al., May 11 2020, BMJ Global Health= masking in the home can reduce in-home transmission by up to 79% if started before symptoms onset. https://gh.bmj.com/content/bmjgh/5/5/e002794.full.pdf”
“The flow physics of COVID-19” Mittal et al., May 1 2020, J. Fluid Mech.: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/476E32549012B3620D2452F30F2567F1/S0022112020003304a.pdf/flow_physics_of_covid19.pdf
“Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks” Konda et al., ACS Nano, April 24 2020: https://pubs.acs.org/doi/10.1021/acsnano.0c03252
“Epidemiological characteristics of COVID-19 in medical staff members of neurosurgery departments in Hubei province: A multicentre descriptive study,” Wang et al., Apr 24 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.04.20.20064899v1
“A rapid systematic review of the efficacy of face masks and respirators against coronaviruses and other respiratory transmissible viruses for the community, healthcare workers and sick patients,” MacIntyre et al., Apr 21 2020, Int J Nursing Studies: https://www.sciencedirect.com/science/article/pii/S0020748920301139
“Universal Masking is Urgent in the COVID-19 Pandemic: SEIR and Agent Based Models, Empirical Validation, Policy Recommendations,” Kai et al., Apr 21 2020, arXiv: https://arxiv.org/pdf/2004.13553.pdf
“Assessment of Fabric Masks as Alternatives to Standard Surgical Masks in Terms of Particle Filtration Efficiency” Mueller et al., Apr 17 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.04.17.20069567v2.full.pdf
“Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering,” Anfinrud et al., Apr 15 2020, N Engl J Med: https://www.nejm.org/doi/full/10.1056/NEJMc2007800
“Transmission of COVID-19 to Health Care Personnel During Exposures to a Hospitalized Patient — Solano County, California, February 2020,” Heinzerling et al., Apr 14 2020, CDC MMWR: https://www.cdc.gov/mmwr/volumes/69/wr/mm6915e5.htm?s_cid=mm6915e5_w
META: “Face Masks Against COVID-19: An Evidence Review,” Howard et al., Apr 12 2020, Preprints: https://www.preprints.org/manuscript/202004.0203/v2
META: “Face masks for the public during the covid-19 crisis,” Greenhalgh et al., April 9 2020, BMJ: https://www.bmj.com/content/369/bmj.m1435
“The Case for Universal Cloth Mask Adoption and Policies to Increase Supply of Medical Masks for Health Workers” Abaluck et al., April 6 2020, SSRN: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3567438
META: Facemasks and similar barriers to prevent respiratory illness such as COVID-19: A rapid systematic review,” Brainard et al., April 6 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.04.01.20049528v1.full.pdf
META: “Physical interventions to interrupt or reduce the spread of respiratory viruses. Part 1 – Face masks, eye protection and person distancing: systematic review and meta-analysis,” Jefferson et al., Apr 7 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.03.30.20047217v2.full.pdf
“Widespread use of face masks in public may slow the spread of SARS CoV-2: an ecological study,” Kenyon, Apr 6 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.03.31.20048652v1
“Could SARS-CoV-2 be transmitted via speech droplets?,” Anfinrud et al., Apr 6 2020, medRxiv: https://www.medrxiv.org/content/10.1101/2020.04.02.20051177v1.full.pdf
“Respiratory virus shedding in exhaled breath and efficacy of face masks” Leung et al., Nat Med, April 3 2020: https://www.nature.com/articles/s41591-020-0843-2
“Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Ma et al., J Med Virol., March 31 2020: https://onlinelibrary.wiley.com/doi/full/10.1002/jmv.25805
“Calibrated Intervention and Containment of the COVID-19 Pandemic,” Tian et al., Mar 16 2020, arXiv: https://arxiv.org/ftp/arxiv/papers/2003/2003.07353.pdf
META: “Effectiveness of N95 Respirators Versus Surgical Masks Against Influenza: A Systematic Review and Meta-Analysis,” Long et al., Mar 13 2020, J Evid Based Med.: https://pubmed.ncbi.nlm.nih.gov/32167245/
“Association between 2019-nCoV transmission and N95 respirator use,” Wang et al., Mar 3 2020, J Hosp Infect.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134426/?report=classic
“Risk of transmission via medical employees and importance of routine infection-prevention policy in a nosocomial outbreak of Middle East respiratory syndrome (MERS): a descriptive analysis from a tertiary care hospital in South Korea,” Ki et al., Oct 30 2019, BMC Pulm Med.: https://bmcpulmmed.biomedcentral.com/track/pdf/10.1186/s12890-019-0940-5
“N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel, A Randomized Clinical Trial,” Radonovich et al., Sept 3 2019, JAMA: https://jamanetwork.com/journals/jama/fullarticle/2749214
“Modeling the Effectiveness of Respiratory Protective Devices in Reducing Influenza Outbreak” Yan et al., Sept 19 2018, Risk Analysis: https://onlinelibrary.wiley.com/doi/full/10.1111/risa.13181
“Risk Factors for Middle East Respiratory Syndrome Coronavirus Infection among Healthcare Personnel,” Alraddadi et al., Nov 2016, Emerg Infect Dis.: https://wwwnc.cdc.gov/eid/article/22/11/16-0920_article
“Surveillance of the Middle East respiratory syndrome (MERS) coronavirus (CoV) infection in healthcare workers after contact with confirmed MERS patients: incidence and risk factors of MERS-CoV seropositivity,” Kim et al., July 27 2016, Clin Microb Infect.: https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(16)30241-5/fulltext
META: “Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis” Smith et al. May 17 2016. CMAJ: https://www.cmaj.ca/content/cmaj/188/8/567.full.pdf
“Transmission Among Healthcare Worker Contacts With a Middle East Respiratory Syndrome Patient in a Single Korean Centre,” Kim et al., Feb 2016, Clin Microbiol Infect.: https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(15)00837-X/fulltext
“Pilot Randomised Controlled Trial to Test Effectiveness of Facemasks in Preventing Influenza-like Illness Transmission Among Australian Hajj Pilgrims in 2011,” Barasheed et al., 2014, Infect Disord Drug Targets: https://pubmed.ncbi.nlm.nih.gov/25336079/
“Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Zhang et al., Sep 2013, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3810906/
“Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Davies et al., Aug 2013, Disaster Med Public Health Prep.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7108646/
“Effectiveness of surgical masks against influenza bioaerosols” Booth et al., May 2013, Journal of Hosp Inf: https://www.sciencedirect.com/science/article/abs/pii/S0195670113000698
“Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks” Milton et al. Mar 7 2013. PLoS Pathog: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591312/
“Effectiveness of Selected Surgical Masks in Arresting Vegetative Cells and Endospores When Worn by Simulated Contagious Patients,” Green at al., Mar 16 2012, Infect Control Hosp Epidemiol.: https://pubmed.ncbi.nlm.nih.gov/22476275/
“The Role of Facemasks and Hand Hygiene in the Prevention of Influenza Transmission in Households: Results From a Cluster Randomised Trial; Berlin, Germany, 2009-2011,” Suess et al., Jan 26 2012, BMC Infect Dis.: https://pubmed.ncbi.nlm.nih.gov/22280120/
“Facemasks, Hand Hygiene, and Influenza Among Young Adults: A Randomized Intervention Trial,” Aiello et al., Jan 25 2012, PLoS One: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0029744
“Is Abdominal Obesity Associated With the 2009 Influenza A (H1N1) Pandemic in Korean School-Aged Children?” Kim et al., Dec 8 2011, Influenza and Other Respiratory Viruses: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1750-2659.2011.00318.x
META: “Physical interventions to interrupt or reduce the spread of respiratory viruses” Jefferson et al., July 6 2011, Cochrane Database Syst Rev.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6993921/
“Impact of Non-Pharmaceutical Interventions on URIs and Influenza in Crowded, Urban Households,” Larson et al., Mar 2010, Public Health Rep.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2821845/
“Mask Use, Hand Hygiene, and Seasonal Influenza-Like Illness Among Young Adults: A Randomized Intervention Trial,” Aiello et al., Feb 15 2010, J Infect Dis.: https://academic.oup.com/jid/article/201/4/491/861190
“Risk factors for SARS infection among hospital healthcare workers in Beijing: a case control study,” Tang et al., Oct 7 2009, Trop Med & Int Health: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3156.2009.02255.x
“Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households: A Cluster Randomized Trial,” Cowling et al., 6 Oct 2009, Ann Intern Med.: https://www.acpjournals.org/doi/full/10.7326/0003-4819-151-7-200910060-00142?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
“A Quantitative Assessment of the Efficacy of Surgical and N95 Masks to Filter Influenza Virus in Patients With Acute Influenza Infection,” Johnson et al., July 15 2009, Clin Infect Dis: https://pubmed.ncbi.nlm.nih.gov/19522650/
“Face Mask Use and Control of Respiratory Virus Transmission in Households,” MacIntyre et al., Feb 2009, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2662657/
“The First Randomized, Controlled Clinical Trial of Mask Use in Households to Prevent Respiratory Virus Transmission,” MacIntyre et al. Dec 1 2008, Int J Infect Dis.: https://www.ijidonline.com/article/S1201-9712(08)01008-4/fulltext
“Risk Factors for SARS Infection Within Hospitals in Hanoi, Vietnam,” Nishiyama et al., Sep 2008, Jpn J Infect Dis.: https://pubmed.ncbi.nlm.nih.gov/18806349/
“Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population,” v.d.Sande et al., July 9 2008, PLoS One: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/
“Factors Associated With Nosocomial SARS-CoV Transmission Among Healthcare Workers in Hanoi, Vietnam, 2003,” Reynolds et al., Aug 2006, BMC Public Health: https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-6-207
“Investigation of the Influencing Factors on Severe Acute Respiratory Syndrome Among Health Care Workers,” Pei et al., June 18 2006, Beijing Da Xue Xue Bao Yi Xue Ban: https://pubmed.ncbi.nlm.nih.gov/16778970/
“Simple Respiratory Mask,” Dato et al., June 2006, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/?report=classic
“Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Jul 1 2005, Am J Trop Med and Hyg.: http://www.ajtmh.org/content/journals/10.4269/ajtmh.2005.73.17#html_fulltext
“Asymptomatic SARS Coronavirus Infection among Healthcare Workers, Singapore,” Wilder-Smith et al., July 2005, Emerg Inf Dis.: https://wwwnc.cdc.gov/eid/article/11/7/04-1165_article
“Factors associated with transmission of severe acute respiratory syndrome among health-care workers in Singapore,” Teleman et al., Nov 8 2004, Epidemiol Infect.: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/55025CCAFE6E5F3B30C31ECB6E73A3D4/S0950268804002766a.pdf/factors_associated_with_transmission_of_severe_acute_respiratory_syndrome_among_healthcare_workers_in_singapore.pdf
“SARS Transmission, Risk Factors, and Prevention in Hong Kong,” Lau et al., Apr 2004, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3323085/
“Mild Illness Associated with Severe Acute Respiratory Syndrome Coronavirus Infection: Lessons from a Prospective Seroepidemiologic Study of Health-Care Workers in a Teaching Hospital in Singapore,” Ho et al., Feb 15 2004, J Infect Dis.: https://academic.oup.com/jid/article/189/4/642/839039
“Risk Factors for SARS among Persons without Known Contact with SARS Patients, Beijing, China” Wu et al., Feb 2004, Emerg Infect Dis: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3322931/
“SARS Among Critical Care Nurses, Toronto,” Loeb et al., Feb 2004, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3322898/
“Effectiveness of Personal Protective Measures in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome,” Yin et al., Jan 2004. Zhonghua Liu Xing Bing Xue Za Zhi: https://pubmed.ncbi.nlm.nih.gov/15061941/
“Illness in Intensive Care Staff After Brief Exposure to Severe Acute Respiratory Syndrome,” Scales et al., Oct 2003, Emerg Infect Dis.: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3033076/
“Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS),” Seto et al., May 3 2003, Lancet: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(03)13168-6/fulltext
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