𝐃𝐨 𝐦𝐚𝐬𝐤𝐬 𝐩𝐫𝐨𝐭𝐞𝐜𝐭 𝐦𝐞 𝐢𝐟 𝐨𝐭𝐡𝐞𝐫𝐬 𝐚𝐫𝐨𝐮𝐧𝐝 𝐦𝐞 𝐰𝐨𝐧’𝐭 𝐰𝐞𝐚𝐫 𝐨𝐧𝐞?

(A follow-up post on the new definition of being a ‘close contact’ – and, hopefully a post to help ease some fear you may have after the new definition)

A few days ago I posted about the updated CDC definitions of being a “close contact” to someone infected with COVID-19. Now the definition includes 15 cumulative minutes of small interactions.

The prison study I cited showed that the employee who became infected wore a mask at all interactions while the infected inmates didn’t. I know that sounded scary to many of you because we go places, sometimes in brief increments, where people don’t wear masks and the anti-mask sentiments are increasing. So, what do those of us who wear our masks do? Let me help address your fears.

𝐃𝐨𝐞𝐬 𝐰𝐞𝐚𝐫𝐢𝐧𝐠 𝐨𝐮𝐫 𝐦𝐚𝐬𝐤𝐬 𝐦𝐚𝐭𝐭𝐞𝐫 𝐚𝐭 𝐚𝐥𝐥 𝐢𝐧 𝐭𝐡𝐨𝐬𝐞 𝐬𝐢𝐭𝐮𝐚𝐭𝐢𝐨𝐧𝐬?
𝐒𝐡𝐨𝐫𝐭 𝐚𝐧𝐬𝐰𝐞𝐫: Yes! It looks like masks play a big role in reducing the amount of virus you could be infected with and that is associated with how sick you become.

𝐋𝐨𝐧𝐠 𝐚𝐧𝐬𝐰𝐞𝐫: Well, first of all – everyone.needs.to.wear.a.mask. It’s one of the easiest and clearest way to get out of this mess we are now in that is projected to be pretty grim as we enter the winter time.

Here’s the evidence showing that masks can protect you even if others aren’t wearing one:

𝟏. 𝐓𝐡𝐞 𝐚𝐦𝐨𝐮𝐧𝐭 𝐨𝐟 𝐯𝐢𝐫𝐚𝐥 𝐥𝐨𝐚𝐝 𝐲𝐨𝐮 𝐠𝐞𝐭 𝐞𝐱𝐩𝐨𝐬𝐞𝐝 𝐭𝐨 𝐥𝐨𝐨𝐤𝐬 𝐭𝐨 𝐛𝐞 𝐫𝐞𝐥𝐚𝐭𝐞𝐝 𝐭𝐨 𝐡𝐨𝐰 𝐬𝐢𝐜𝐤 𝐲𝐨𝐮 𝐠𝐞𝐭. In medical terms that’s called the viral inoculum – the initial dose of virus that a person takes in. (Look at the Gahndi et al paper in the sources.)

2. 𝐕𝐢𝐫𝐚𝐥 𝐥𝐨𝐚𝐝 𝐢𝐬 𝐚𝐬𝐬𝐨𝐜𝐢𝐚𝐭𝐞𝐝 𝐰𝐢𝐭𝐡 𝐢𝐥𝐥𝐧𝐞𝐬𝐬 𝐬𝐞𝐯𝐞𝐫𝐢𝐭𝐲 𝐚𝐧𝐝 𝐝𝐞𝐚𝐭𝐡. A study in NYC found that each additional unit of viral COVID-19 RNA detected increased the risk of death by 7%. In the medical world, 7% can compound pretty quickly.

3. 𝐄𝐚𝐫𝐥𝐲 𝐢𝐧 𝐭𝐡𝐞 𝐩𝐚𝐧𝐝𝐞𝐦𝐢𝐜, 𝐚 𝐬𝐭𝐮𝐝𝐲 𝐢𝐧 𝐂𝐡𝐢𝐧𝐚 𝐟𝐨𝐮𝐧𝐝 𝐭𝐡𝐚𝐭 𝐭𝐡𝐞 𝐦𝐞𝐚𝐧 𝐯𝐢𝐫𝐚𝐥 𝐥𝐨𝐚𝐝 𝐢𝐧 𝐬𝐞𝐯𝐞𝐫𝐞 𝐜𝐚𝐬𝐞𝐬 𝐰𝐚𝐬 𝟔𝟎 𝐭𝐢𝐦𝐞𝐬 𝐡𝐢𝐠𝐡𝐞𝐫 𝐭𝐡𝐚𝐧 𝐭𝐡𝐚𝐭 𝐨𝐟 𝐦𝐢𝐥𝐝 𝐜𝐚𝐬𝐞𝐬. So, again – viral load matters.

4. 𝐌𝐚𝐬𝐤𝐬 𝐚𝐫𝐞 𝐧𝐨𝐭 𝐩𝐞𝐫𝐟𝐞𝐜𝐭 𝐛𝐮𝐭 𝐭𝐡𝐞𝐲 𝐜𝐚𝐧 𝐟𝐢𝐥𝐭𝐞𝐫 𝐨𝐮𝐭 𝐭𝐡𝐞 𝐦𝐚𝐣𝐨𝐫𝐢𝐭𝐲 𝐨𝐟 𝐭𝐡𝐞 𝐥𝐚𝐫𝐠𝐞 𝐝𝐫𝐨𝐩𝐥𝐞𝐭 𝐩𝐚𝐫𝐭𝐢𝐜𝐥𝐞𝐬. Think of these large droplet particles as when your kid sneezes on you. You can see that. The smaller particles that are airborne can’t be seen and masks do a relatively good job at keeping some of those out too. Certain masks work better than others and I’ll link to a post about that at the end.

5. 𝐀𝐧𝐢𝐦𝐚𝐥𝐬 𝐬𝐭𝐮𝐝𝐲 𝐩𝐫𝐨𝐯𝐢𝐝𝐞 𝐬𝐭𝐫𝐨𝐧𝐠 𝐞𝐯𝐢𝐝𝐞𝐧𝐜𝐞 𝐭𝐡𝐚𝐭 𝐦𝐚𝐬𝐤𝐬 𝐩𝐫𝐨𝐭𝐞𝐜𝐭 𝐮𝐬 𝐟𝐫𝐨𝐦 𝐡𝐢𝐠𝐡𝐞𝐫 𝐝𝐨𝐬𝐞𝐬 𝐨𝐟 𝐂𝐎𝐕𝐈𝐃-𝟏𝟗 𝐢𝐟 𝐞𝐱𝐩𝐨𝐬𝐞𝐝. With COVID-19, we can’t ethically give people different doses of the virus on purpose and see how sick they get. But, animal studies have been done. In a study with hamsters, those infected with higher doses of COVID-19 had worse outcomes than those infected with smaller amounts. Again, viral load matters.

Here’s the kicker: Another study with hamsters put masks on them. (Y’all, I hope this makes you chuckle a little bit. Because it’s 2020 and laughter is good for our immune systems.) Ok, so they weren’t real individual masks – two groups of hamsters (one infected group and one healthy group) were separated by a surgical mask partition between cages. The surgical masks protected the healthy hamsters from the infected hamsters from any infection at all in many of them. If the healthy ones were infected, the infections were mild.

***Wear your mask, friends. Anytime you are around people – even if they aren’t wearing a mask. Masking, even if imperfect, provide strong protection for us, our families, and neighbors.

Please just wear one. I don’t like to continually remind all of us of what the grim predictions look like in the next few months. Masks can reduce those grim predictions by 70,000 to 160,000 deaths by February 2021.***

-Friendly neighbor epidemiologist


1. Close contact definition post: https://tinyurl.com/y26nuedg

2. Gandhi paper:https://ucsf.app.box.com/s/blvolkp5z0mydzd82rjks4wyleagt036

3. NYC study:https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30354-4/fulltext

4. China study: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30232-2/fulltext#%20

5. Hamster studies:https://www.pnas.org/content/117/28/16587

6. COVID-19 death predictions:https://covid19.healthdata.org/united-states-of-america?view=total-deaths&tab=trend

7. Which mask works the best? https://tinyurl.com/y5rfqhqk

8. Other mask posts:

1. Masks work: The strongest evidence we havehttps://tinyurl.com/yxkymuofhttps://tinyurl.com/y2ux4owk
2. Mask 101: Why they work, exposure time, how to wear and disinfect your mask correctlyhttps://tinyurl.com/yxvayp76https://tinyurl.com/y6zxl2u3
3. Myth-busters for mask: A LONG post debunking common myths about masks (masks work really well, clearing up what the surgeon general/WHO said, CO2 fears) https://tinyurl.com/y642sefb
4. Did the Surgeon General or WHO say not to wear masks?https://tinyurl.com/y4d8ghk2
5. Sheltering in place workshttps://tinyurl.com/y66halh3https://tinyurl.com/y2cn5vdq
6. Why state-wide mask mandates work! – https://tinyurl.com/yxu6gl4r
7. A reminder of when someone is contagious and the importance of masks (and a note on bipartisan science) – https://tinyurl.com/y4rfjmc5

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