Coronavirus Episode 20: What’s the Deal with Masks?
I’ve seen so much misinformation out there about masks it’s crazy. Should you wear one? Yes, no, maybe? What kind of mask? Is this just wasting PPE on the worried well or will it help the average at-risk person protect themselves? Is there a conspiracy going on due to our mask shortage? Let’s dig in.
The Media on Masks
I’ve read a number of media stories on masks. Most are fiction and many seem to be trying to justify that we should be wearing masks merely as clickbait or to build a conspiracy. So let’s actually look at the hard science, and not one small study or rumor hand-picked to sell eyeballs to advertisers.
What are we Protecting Ourselves From?
The coronavirus is aerosolized when patients cough or sneeze. The virus can hang in the air in small water droplets for hours (UNDER IDEAL CONDITIONS IN A LAB) (20). However, in any type of breeze, these droplets are scattered and the virus then becomes much less densely distributed. Hence, the idea behind healthy people wearing masks is that we’re protecting ourselves from these small water droplets containing the virus.
Types of Masks
There are two main broad categories of masks we’re talking about here: surgical or N-95. So what’s the difference between these masks? (1)
- Surgical-This is what a doctor wears during certain procedures. This protects the wearer from only larger water droplets and NOT smaller droplets. The masks filter out between 10-90% of all particles, depending on the manufacturer (2). There is also a high likelihood that bad stuff can get around the mask as they are poorly fitted to the face.
- N-95-The “95” literally stands for the ability to filter out 95% of airborne particles. That includes small water droplets. These masks are better fitted to the face, so they allow less bad stuff to get around the mask.
It’s critical to note that surgical masks DO NOT perform the same as N-95 masks. A recent lab study of five different “good” surgical masks found that 80–100% of subjects failed an OSHA-accepted fit test with 12–25% leakage around the mask (3). The worst N-95 masks performing the same test showed 1% leakage.
In addition, three studies have shown that surgical masks perform so poorly, that infection rates during surgeries were not any different when the staff didn’t wear a surgical mask! (4-6) Other studies have come up with similar conclusions about the poor performance of these masks (10-13).
To see how different surgical and N-95 masks really are with respect to airborne viral protection, look no further than a study that compared the two in nurses. The risk of contracting a SARS virus (similar to the novel coronavirus) was significantly lower with consistent use of N95 masks but not with consistent use of a surgical mask (19).
The Research on You Wearing a Surgical Mask
This is a great sentence from a recent Lancet article on this topic, “Evidence that face masks can provide effective protection against respiratory infections in the community is scarce, as acknowledged in recommendations from the UK and Germany.” (7) A 2009 study that tested surgical masks to prevent the people in a household from contracting a respiratory virus found that this didn’t work, but that could have been because people who had the masks didn’t wear them all the time (8).
The Research on Someone Who Is Sick Wearing a Surgical Mask
There is some evidence that wearing surgical masks might be effective at reducing the infectious particles emitted by patients who have many different respiratory illnesses (15-17). One study found a 43% reduction in respiratory viral infections in immune comprised patients when everyone (patients, visitors, and healthcare workers) wore surgical masks (18). However, these were not patients who had a normal and functioning immune system.
Maybe We Should All Wear Masks to Slow the Spread of the Disease?
I like studies that try to replicate real-life conditions, especially when some are contemplating asking everyone to wear a mask to slow the spread of COVID-19. A University of Michigan study is, therefore, a good one to review (21). They randomized more than a thousand students to either wear a mask 6 hours a day and use hand sanitizer, just use the mask, or a control group. The hand sanitizer kind of worked, but the masks did nothing to stop the spread of the flu virus.
There is also a review of 17 studies that tried to prove that wearing masks would slow the spread of respiratory viruses, but the findings were mixed (22). They concluded, “None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.” The authors did note that if masks were part of an early intervention strategy and everyone used them correctly, then wearing masks might work to prevent the spread of a respiratory virus. However, we’re not early nor is every American going to correctly and consistently use masks.
Home Made Masks
The National Institute for Occupational Safety and Health (NIOSH) funded a study on whether clothing such as sweatshirts, t-shirts, and scarfs would work in healthcare settings (9). They concluded that these items could only provide marginal protection against small particles.
A randomized controlled trial comparing the ability of medical and cloth masks to prevent healthcare workers from contracting the flu found that those workers wearing cloth masks were 13 times more likely to get a respiratory viral infection than those wearing medical masks (14).
In my opinion, the whole mask controversy has become somewhat politicalized and is now feeding on conspiracy theories. The storyline goes something like this: we don’t have enough masks because our government didn’t take this threat seriously, hence that’s the real reason they’re telling us not to wear masks when they know it will keep us safe, hence, we’re all screwed. However, when you dig into the actual research, that’s not what you find. Instead, you find that the controversy over masks and respiratory virus transmission has been a thing for decades. You also find that the research supports:
- Surgical masks have not been shown to prevent you from getting a respiratory virus. The research that supports that concept is VERY WEAK.
- Cloth masks are even worse.
- If you’re sick, there is some evidence that wearing a surgical mask can help reduce your chances of spreading the virus.
- If you have an N-95 mask, this will help you, but please donate it to the nearest hospital.
The upshot? I know it’s disappointing, especially with all of the sewing going on right now, to hear that cloth masks are unlikely to help. Also, it’s also disappointing that surgical masks are very unlikely to help you. However, the CDC is right. Do not wear a mask unless you’re the one who is sick.
(1) Centers for Disease Control and Prevention. Understanding the Difference. https://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInfographic-508.pdf Accessed 4/1/20.
(2) Centers for Disease Control and Prevention. N95 Respirators and Surgical Masks. https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/ Accessed 4/1/20.
(3) Oberg, T., and L. M. Brosseau. 2008. Surgical mask filter and fit performance. American Journal of Infection Control 36, (4) (May): 276-82.
(4) Orr, N. W. 1981. Is a mask necessary in the operating theatre? Annals of the Royal College of Surgeons of England 63, (6) (Nov): 390-2.
(5) Mitchell, N. J., and S. Hunt. 1991. Surgical face masks in modern operating rooms—a costly and unnecessary ritual? The Journal of Hospital Infection 18, (3) (Jul): 239-42.
(6) Tunevall, T. G. 1991. Postoperative wound infections and surgical face masks: A controlled study. World Journal of Surgery 15, (3) (May-Jun): 383,7; discussion 387-8.
(7) Feng S, Shen C, Xia N, Song W, Fan M, Cowling BJ. Rational use of face masks in the COVID-19 pandemic. Lancet Respir Med. 2020 Mar 20. pii: S2213-2600(20)30134-X. doi: 10.1016/S2213-2600(20)30134-X.
(8) MacIntyre CR, Cauchemez S, Dwyer DE, et al. Face mask use and control of respiratory virus transmission in households. Emerg Infect Dis. 2009;15(2):233–241. doi:10.3201/eid1502.081167
(9) Rengasamy S, Eimer B, Shaffer RE. Simple respiratory protection—evaluation of the filtration performance of cloth masks and common fabric materials against 20-1000 nm size particles. Ann Occup Hyg 2010 Jun 28;54(7):789-98
(10) Saunders-Hastings P, Crispo JA, Sikora L, et al. Effectiveness of personal protective measures in reducing pandemic influenza transmission: A systematic review and meta-analysis.Epidemics 2017 Sep;20:1-20
(11) Cowling B J, Zhou Y, Ip DKM, et al. Face masks to prevent transmission of influenza virus: a systematic review. Epidemiol Infect 2010 Jan 22;138(4):449-56
(12) bin‐Reza F, Chavarrias VL, Nicoll A, et al. The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence. Influenza Other Respir Viruses 2011 Dec 11;6(4):257-67
(13) MacIntyre CR, Zhang Y, Chughtai AA, et al. Cluster randomised controlled trial to examine medical mask use as source control for people with respiratory illness.BMJ Open 2016 Dec 30;6(12):e012330
(14) MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.BMJ Open 2015 Apr 22;5(4):e006577
(15) Milton DK, Fabian MP, Cowling BJ, et al. Influenza virus aerosols in human exhaled breath: particle size, culturability, and effect of surgical masks.PLoS Pathog 2013 Mar;9(3):e1003205
(16) Stockwell RE, Wood ME, He C, et al. Face masks reduce the release of Pseudomonas aeruginosa cough aerosols when worn for clinically relevant periods.Am J Respir Crit Care Med 2018 Nov 15;198(10):1339-42
(17) Dharmadhikari AS, Mphahlele M, Stoltz A, et al. Surgical face masks worn by patients with multidrug-resistant tuberculosis: impact on infectivity of air on a hospital ward.Am J Respir Crit Care Med 2012 May 15;185(10):1104-9.
(18) Sung AD, Sung JA, Thomas S, et al. Universal mask usage for reduction of respiratory viral infections after stem cell transplant: a prospective trial.Clin Infect Dis 2016 Oct 15;63(8):999-1006
(19) Loeb M, McGeer A, Henry B, et al. SARS among critical care nurses, Toronto.Emerg Infect Dis 2004 Feb;10(2):251-5
(20) The Centers for Disease Control and Prevention. How Coronavirus Spreads. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html Accessed 4/1/2020.
(21) Aiello AE, Perez V, Coulborn RM, Davis BM, Uddin M, Monto AS. Facemasks, hand hygiene, and influenza among young adults: a randomized intervention trial. PLoS One. 2012;7(1):e29744. doi:10.1371/journal.pone.0029744
(22) Bin-Reza F, Lopez Chavarrias V, Nicoll A, Chamberland ME. The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence. Influenza Other Respir Viruses. 2012;6(4):257–267. doi:10.1111/j.1750-2659.2011.00307.x