COVID Transmissions for 9-25-2020
Good morning! It has been 312 days since the first documented human case of COVID-19.
Some headlines today; enjoy! I also want to note that there will not be a newsletter for 9/28 because of Yom Kippur. Instead, I will return to regular posting on 9/29.
Also, I am essentially now back to complete health. My COVID-19 PCR test returned negative, which is largely good news.
As usual, bolded terms are linked to the running newsletter glossary.
Keep the newsletter growing by sharing it! I love talking about science and explaining important concepts in human health, but I rely on all of you to grow the audience for this:
Now, let’s talk COVID.
COVID-sniffing dogs in Helsinki
The New York Times reports today on the use of trained dogs to detect COVID-19 infection in Finland, specifically in the Helsinki airport: https://www.nytimes.com/2020/09/23/world/europe/finland-dogs-airport-coronavirus.html
Dogs are known for their sense of smell, but viruses are not particularly known for making people smell a specific way. In fact, COVID-19 is best known, in the olfactory world, for inhibiting some patients’ ability to smell things at all.
So, the big question here, as stated by one of the members of my thesis committee, is:
I am also curious about the sensitivity and specificity of the canine-COVID test. Can a dog tell the difference between an influenza virus infection and a SARS-CoV-2 infection? Why? The viruses do not contain wildly different chemicals—lipids, RNA, and proteins are the main constituents of both. Could a dog tell the difference between an infection with SARS-CoV-2 and a human-adapted coronavirus?
Time will tell! For now, this is a fun and intriguing idea.
Vented vs nonvented masks
Some time back, the idea that masks with “vents,” or more appropriately, valves for exhalation, were more dangerous than masks without them began to take root in the community at large. This is based on a good hypothesis. The valve lets air out relatively freely, passing it by some kind of baffle that seals the mask when you inhale. That would suggest that exhalations are not filtered, making the vented mask better for protecting the wearer than for protecting others.
Since we wear masks to protect others from infection, it was thought that this made vented masks a liability.
I heard this from state authorities and even the CDC, but I did not see any evidence to support it. Yes, you can feel the air flowing out of the valve, but you can also feel air flowing out from the unsealed edges of a cloth mask. Most of the masks we wear seem to be poorly sealed, because they are not medical masks meant for having a good seal.
Yet the advice continued to say not to wear valved or vented masks. I wanted to see data showing projection of exhalations from a valved/vented mask vs a cloth mask. No one seemed to have such data. I like a good hypothesis, but I want the data.
This study, in Scientific Reports, looked at a large number of different features of masks and considered a number of different things that might affect particle emissions from masks. Interestingly, they tested particle emissions from cloth vs KN95 (nonvalved) and N95 (valved) masks, and found that the cloth masks had generally more particle emissions while the N95s, valve or no, had similar levels of particle emission.
This appears to justify my doubts, but a word of caution—the researchers here (one of whom, Dr. Nicole Bouvier, is a former colleague of mine) did not have a large enough supply of the valved N95 mask to do a robust test of it compared to the others.
Now, this paper is not primarily about valves, but I think this justifies my reasons for doubting this advice about valves and wanting to see data. I’d like to explore the paper more deeply in a future edition of the newsletter, because there’s a lot here.
By the way, I would still recommend you not wear masks with valves. It’s in the CDC’s recommendations and I think you should follow them. This one study is not definitive at all.
What am I doing to cope with the pandemic? This:
Isolating?
My COVID results were negative! I can go outside again!
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No corrections since last issue.
Thanks for reading, everyone! Yom Kippur will be a day of reflection and thoughtful self-analysis for me, and I hope to come out of it refreshed and looking forward to a good new year. New Year or not I hope you all find the same over the weekend.
See you all next time.
Always,
JS