September 1, 2020

Epidemiology and Masks

Well, it has been a wild ride. Six months since we felt the speeding train of COVID-19 bearing down on Seattle in early March. I wrote my first post about the pandemic on March 2. Little did I know that I would be writing 6 months later and that I would enjoy it so much. At the time, we thought we were going to end up like Italy and New York, overwhelmed with a surge of patients. The tidal wave never came. Luckily, our city shutdown and did all the things we could to limit the spread. Still, many have become ill and too many have died.

When I first wrote about the virus, we knew very little, patients were treated as if they had another coronavirus, SARS. Now we know that this virus behaves differently in unexpected ways. We have needed to be adaptable and learn what works and what doesn’t work. In epidemiology, they call it “Updating your priors”, meaning we need to continually re-assess and update our expectations, beliefs, and knowledge. The New York Times has an interesting article about how to think like an epidemiologist. It is based on thinking about probability and uncertainty, from the work of Thomas Bayes in the 18th century who devised “Bayes Theorem”. This is actually a useful skill for life, if we can all learn to let go of our expectations more readily and live with uncertainty.

One “prior” expectation that has had to be updated is how the virus is transmitted. The “prior” knowledge and belief was that it was transmitted via respiratory droplets, which would quickly fall to the floor or surfaces due to gravity, hence the emphasis on hand washing. Now the evidence supports the virus being airborne in smaller particles that stay aloft, which has shifted public health recommendations.

The whole 6 months has been one of constantly updating our knowledge and living with uncertainty. The good news is that we have learned so much. We are doing a much better job of helping patients survive with new approaches to treatment like high flow oxygen and “tummy time”, when patients lie on their bellies instead of their backs to improve their breathing. We are preventing more infections and spread. As long as people follow the new, updated advice, of course. This uncertainty and changing advice has made it harder for people that want certainty. It also increases their skepticism, when the advice changes.

Advice about mask wearing is a good example of confusing and changing recommendations. Now the data is much clearer that masks work. Wearing them is much more accepted in many places, still resisted in some. I am including some fresh information on masks for your consideration. Time has a good article on masks, especially homemade ones. I trust this CDC advice on masks and how to wear and clean them. This story describes a way to decontaminate an N-95 mask so it can be used again. This Seattle Time article talks about a way to adapt a face shield to be safer by having it wrapped in a hood, but still best with a mask.

And next week, our priors will need to be checked and updated once more, as we learn more about COVID-19. It is what I love about medicine, the constant challenge to keep learning.

Wash your hands, cover your nose, keep safe six, outdoors, and stay flexible.

And finally, my caveat is that this is my experience and my opinions, which are subject to change as more information is available, and not related to the organization I work for. Thanks for reading.

https://www.nytimes.com/2020/08/04/science/coronavirus-bayes-statistics-math.html

https://betsybrownmd.substack.com/p/march-2-2020

https://en.wikipedia.org/wiki/Bayes%27_theorem

https://www.medpagetoday.com/infectiousdisease/covid19/88301

https://time.com/5880867/face-masks-coronavirus/

https://www.sciencedaily.com/releases/2020/08/200827130614.htm

https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/about-face-coverings.html

https://www.seattletimes.com/seattle-news/health/can-i-use-a-face-shield-instead-of-a-mask/