COVID Transmissions for 4-7-2021
It can transmit through the air
Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.
It has been 506 days since the first documented human case of COVID-19. In 506, King Alaric II of the Visigoths created the Lex Romana Visigothorum, a code of laws covering Romans who now lived in the Visigothic Kingdom. This Kingdom extended down across central France into Iberia. This book became the basis for law and justice in the Visigothic Kingdom for some hundreds of years until the Visigoths were conquered by the Umayyad Muslim Caliphate. Today, it is one of the best known sources preserving Roman laws.
In the COVID-19 context, this book interests me because it was a set of old laws rewritten to reflect a new reality. I wonder what we will do with the laws and norms of our old status quo as we rewrite them after this pandemic. Some rewriting has already happened. I imagine there is more yet to come.
Still, this code of laws is interesting for how it transmitted Roman Law down through the centuries.
Today I’m going to talk about transmission a lot: headlines on airborne and surface-based transmission of SARS-CoV-2.
As usual, bolded terms are linked to the running newsletter glossary.
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Now, let’s talk COVID.
The unmasked singer: definitely still not a great idea, also demonstrates the airborne component of COVID-19 spread
No news yet that I’ve seen on singing in groups with masks on (I know some of you have asked about this), but I did happen upon this paper from Emerging Infectious Diseases that looks at a superspreader event in an Australian religious setting, where the spread seems to have been driven by singing:
https://wwwnc.cdc.gov/eid/article/27/6/21-0465_article
In this case, a choir member sang at multiple services where people were unmasked, and 12 cases of COVID-19 resulted. What’s interesting especially is that these cases were people who were seated below the choir loft in the church, at a considerable remove from the unmasked index case. Take a look at this map from the paper:
There was no evidence of close physical contact for these patients with the index case. All of them were seated at least 15 meters away.
This is with little doubt an airborne spread event. It may be an unusual event, created by the ambient conditions: singing, which projects a lot of virus into the air, poor ventilation, which allows respiratory particles to accumulate in the air, and the singer being at or near peak infectiousness when they performed.
While these special circumstances may be required for airborne transmission, I would note that they are hardly rare circumstances. Peak infectiousness for COVID-19 may actually be before any symptoms appear, so there may be a lot of people out there right now who don’t know they’re capable to spreading the virus. Poor ventilation plagues old buildings; religious institutions are often in older buildings. Singing is a big part of a lot of gatherings.
I don’t know how definitively we can demonstrate airborne transmission in other settings, but I do know, from this report, that it can happen under these specific conditions. That’s something to keep in mind.
CDC guideline update: surface transmission isn’t really a thing
There has been extensive discussion of this already, but the CDC has finally updated their guidelines to acknowledge that SARS-CoV-2 doesn’t really transmit much on surfaces: https://www.cdc.gov/coronavirus/2019-ncov/more/science-and-research/surface-transmission.html
All the incessant scrubbing down of every surface? Not pointless, though. It still prevents transmission of other diseases that you’d probably rather not catch during a pandemic.
Still, based on review of available data, the CDC thinks that the chance of a surface transmission event is about 1 event in 10,000 exposures to contaminated surfaces. For reference, about 1 in 20,000 eggs is contaminated with salmonella bacteria, so any time you’ve eaten a runny yolk, you’ve been exposing yourself to risk on a similar order of magnitude. Of course COVID-19 and salmonella gastroenteritis have very different risks of killing or disabling an infected person, but I think this sort of puts it into perspective, especially since (I think) you’re much more likely to eat 20,000 eggs in your lifetime (it’s about 27 years worth of 2-egg breakfasts) than you are to have touched 10,000 COVID-19 contaminated surfaces within the last year. I could be wrong, though. I don’t know how many surfaces the typical person touches in a day, or how likely they are to be contaminated with COVID-19.
Still, I think that this risk level is low. I think surface transmission is far from the most likely way you could get COVID-19. To continue my tortured analogy, I think you’re far more likely to avoid eating raw chicken for salmonella risk than to avoid runny egg yolks. Similarly, the risk of COVID-19 from airborne or droplet exposures is much, much higher—with maybe 5-15% of exposure events leading to transmission—than this 0.01% chance of transmission from surfaces.
So, I think we can put the fears about surfaces to bed. I still recommend handwashing regularly, though. Handwashing probably figures into this risk estimate, and helps avoid surface transmission. Also, trust me—there’s a lot of stuff out there besides COVID-19 that is better washed off.
The CDC also still recommends surface cleaning in areas that have been occupied by a person with a confirmed case of COVID-19.
Read the full guidance for more details.
What am I doing to cope with the pandemic? This:
Epic space battles
I’ve mentioned this sporadically before, but I’m a player of the mobile game EVE:Echoes. It’s a stripped-down version of the even more complicated game, EVE:Online, which is about a bunch of immortal clones faring their way through lawless space to try and make some money. It’s a “sandbox” game where nearly anything goes. Scams, fraud, and deception are rampant. Anyone you meet is much more likely to shoot you than befriend you.
Against this backdrop, a series of player “nations” emerges. I’m part of one, and yesterday we were attacked by mercenaries who had been paid by someone who doesn’t like us to come destroy a very valuable economic asset that we own.
We responded with a fleet of around 120 pilots, each flying their own ships. It’s remarkable to see how such a large fleet is coordinated. Everyone is an independent actor, and it’s like herding cats. Targets need to be called, all in the chaotic battle environment where the individuals being commanded are also being shot at.
All told, today’s battle did enough damage in in-game currency that it would take $242 real-life dollars to replace if purchased from the in-game store. That’s not a massive impact necessarily—an equivalent amount can be earned in a day by a much smaller number of players, for free—but I find the exchange rate interesting, because it gives a sense of what’s “on the line” for people in such a fight. Getting shot at means losing something.
Under those conditions you see real dynamics of human leadership. A fleet commander has to keep everyone focused, on task, and also needs to fight the battle with their own ship. That fleet commander needs to likewise choose the right targets and make the right calls, because even if everyone listens to them, they can still make mistakes.
The reason I’m lovingly detailing this experience isn’t just because it was some fun I had. It also makes me better appreciate the skills it takes to lead people. I can imagine that many leaders through the pandemic felt similarly challenged to keep people on task while they are frightened, to keep people hopeful and focused, while also struggling to make the right decisions in unprecedented times.
I have a lot of respect for anyone who was a leader of anything through this time. It can’t have been easy.
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See you all next time.
Always,
JS
That CDC brief on surface transmission is annoying vague about certain things.
Note about your analysis: that's 1 in 10,000 *per surface touched*. If you touch 100 contaminated surfaces per day, the risk would appear to rise to 1% per day! Very few people eat 100 eggs per day. (I know of one toxicologist who did it at least once, but that guy used to do some weird stuff.)
Also, what's a "surface" for this purpose? Each door handle, each light switch, each chair back? You could reach 100 easily, if you're in an area with high incidence of infection.
OTOH, it actually says "less than" 1 in 10,000, so ... did I mention it's annoying vague?
Then again, maybe it doesn't take handwashing into account? It says things like, " Hand hygiene is a barrier to fomite transmission and has been associated with lower risk of infection." and "The risk of fomite transmission can be reduced by wearing masks consistently and correctly, practicing hand hygiene, cleaning, and taking other measures to maintain healthy facilities." It doesn't (as you wrote) make clear if its risk assessment does, or does not, include hand hygiene, but I have to think not. If it did, then would this not imply that it also takes into account mask wearing (How is that relevant to surface transmission), cleaning, and "other measures"? And isn't "other measures" ... annoying vague?