Monday, July 13, 2020

The Fog of Coronavirus: No Bright Lines

An adaptive mind-set for coping with COVID risk (+ adaptive updates at end)

At least six feet apart? More or less? The problem is that no bright lines bound a fog! Generals speak of “the fog of war” – we are at war with a virus that literally is a fog.

People like simple rules.  “Stay six feet apart.”  Bright enough, but do I really have to? Is it really enough? Oh, that is if it lasts more than fifteen minutes?  Inside or outside?  Downwind?  Talking or singing?  Loudly?  Emerging research summarized in MIT Tech Review and recently endorsed by the WHO shows this is far more complex and unpredictable than the six foot rule suggests.  Do masks really help?  When?  Do schools and offices reopen?  How?  Again, the answers seem to be “it depends, and our advice may change.”  Individuals and businesses need to be smart about this at all times.

Humans have been bred to be good at the complex calculus of throwing a spear or jumping a crevice, but we have less inbred ability to think about problems without immediate feedback -- like the spread of a virus.

Epidemiologists offer simple rules with bright lines.  But those are gross simplifications.  Apply them simplistically at your peril – and the peril of those around you.  I am no epidemiologist, but was educated in the science of decision making under risk and uncertainty and of optimizing in the real world.  We must all do that science as best we can.  When hunting for game or playing ball, simple rules about where to look, run, and aim are just the start – we layer on a rich intuitive calculus incorporating all we know about the task and its dynamics. Unfortunately, few of us learn even the basics of the dynamics contagion (and the science is still emerging). 

Here are some suggestions on structuring our thinking.  But this above all:  use good judgement all the time, every time, and try to make it both informed and thoughtful, with situational awareness to the current context.  This applies to individuals and groups, including businesses, schools, and other organizations.

It floats though the air with the greatest of ease…

It seems the coronavirus is transmitted primarily (but not only) as an aerosol or droplets that can be inhaled or touched -- directly or indirectly, and that even those without symptoms can transmit infection.  The aerosol seems most pervasive and significant, although droplets and indirect contact remain a concern.  So we need to consider not only what we touch and where we cough or sneeze, but how we might inhale the aerosol.  It seems that aerosol can float far more than 6 feet, and longer than 15 minutes.

Also, it seems “the dose makes the poison.” One might expect a single virus particle to be enough to cause contagion, but apparently it takes some quantity over time to overpower our immune system.  The more exposure the greater risk.  That is a complex and uncertain function of distance, time, and the number of exposures (and also depends on how healthy your immune system is).  Familiarity breeds viruses.

An analysis in Science (worth careful reading) shows how fuzzy this aerosol is -- significant amounts of coronavirus can travel much more than six feet under common conditions. An aerosol is literally a fog. Try putting a bright line around that! Ideally, we should consider the fluid dynamics of the air we are in. How much aerosol or droplets of what sizes? What level of exhalation? What airflow from a carrier to us.  How much get through a mask?  Studies of contagion airflow in a Wuhan restaurant and from runners show how tricky this can be.

Risk is complex and uncertain

Even experts find this interplay daunting. Tom Frieden, former CDC head, said (about broader issues), “People keep asking me, ‘What’s the one thing we have to do?’ The one thing we have to do is to understand that there is not one thing.”  It seems we must constantly do our own calculus in each situation as it emerges.  We must consider the nature of the game and the current conditions and intuit the dynamics (and aerodynamics) -- just as when we hunt or play ball.

Furthermore, we need to understand the basics of probability. People argue “going to a bar is no worse than going to a supermarket.”  Wrong on two levels. First, the exposure in a bar is likely closer and longer. More importantly, even if the risk was equal, it is how often you take risks that determines total risk. You can play Russian roulette once or twice and likely survive. Ten or twenty times and you will almost certainly die.  We must weigh level of risk, duration, and frequency.

Authorities like the CDC should be teaching us these underlying principles, so we can do our own calculus in each context.  But it is on each of us to read widely, apply critical thinking to weed out the junk, and use practical guides like the posts of immunologist Erin Bromage or similar coverage in general or business publications.

“In this together” – we are our brother’s keeper

Equally important, we need to help others to do likewise.  Covid-19 presents a life or death problem of optimizing individual risk and, as social creatures who infect one another, that requires optimizing collective risk.  We have an ongoing collective responsibility for being informed and thoughtful not just about our own risk, but our risk to others. 

We need to think about the social bubbles of those we will take the risk of being close to much of the time.  Within a few small, carefully controlled bubbles we might not wear masks, just as within family units.  But is now seem clear that we need to wear masks whenever anywhere near others not in our bubble.  We need to get everyone to understand that is not just so much for our own safety, but for that of others.  This is not a question of individual freedom, but of our responsibility as members of society (just as we do not drive drunk on public streets, even if we are a free-spirited daredevil).

At the macro level of groups, we have similar fuzziness that depends on the current context and dynamics.  We are realizing that we must go beyond simple on/off rules.  Hybrid” models are emerging.  Not only must such models be carefully phased in depending on current conditions, they must remain adaptive to tightening or loosening in response to changing conditions. 

Agility in risk management

Soldiers navigate the fog of war with a continuous OODA loop (Observe-Orient-Decide-Act).  Individuals and businesses should seek to do the same, and instill this in all of their family, team, or community.  Systematization is an essential tool, but understand its limits.  Every business should have an ongoing program of guidance and education for applying OODA loops as long as the virus is not fully controlled.

We are developing metric scorecards and prediction models to assess the risk of social spreading in each locale, but our understanding of the science is evolving.  Making this even more complex, recent evidence suggests the virus has been mutating faster than first thought, so any rules that make sense today might not be so good next week.

There is huge pressure to relax these annoying constraints when conditions permit – but we must apply a carefully considered gradient -- not just a simple, binary risk-on/risk-off cycle -- in our vigilance level.  To do that all of us need to track the key indicators to know when risk of community spread is high or low.  And because our knowledge and the virus are evolving, we all, at each level, must also apply an OODA loop to the basic principles of our strategy – evolving that as we learn more. OODA applies at all levels -- to our everyday activity, our basic tactics, and our broad strategy. Don't get stuck "fighting the last war."

Good leaders will try their best to help all of us to “be smart.”  Smart businesses will care about their customers, employees, and reputations.  That may warrant empowering a “chief health officer.”  Entrepreneurs will seek opportunities to help in those efforts (and profit from that).  We are bound as humans by a social contract to be careful for one another.  Like it or not, we are truly in this together.  Institutional dysfunction leads to health dysfunction.  We need effective government and institutions that foster social trust.  The US has that in some locales, but overall, it is tragically lacking (as the WSJ reports).

We are all living in an era of unusual personal risk – each of us must be smart and situationally aware about managing the risks we take for ourselves and those we may infect.

Coda: context matters...and changes

As I was finalizing this post, this sad example underlined the importance of context -- and how it changes. Anthony Fauci is now being criticized (by the White House!) for his statement back on April 3:  "…There’s no reason to be walking around with a mask..."

In context, he also said (emphasis added):  "...Right now in the United States, people should not be walking around with masks. ...when you think masks, you should think of health care providers needing them and people who are ill. ... It could lead to a shortage of masks for the people who really need it." At the time, it was not foolish at all. The times changed, and Fauci's statements changed with the context. 

Pay attention to the situation. Don't be a Covidiot!

[Update 4/18/21:] The Swiss cheese model

A very simple metaphorical model for dealing with the fog, in the spirit outlined here, is the Swiss Cheese Respiratory Pandemic Defense, as nicely explained in the NY Times with the image above.

This illustrates the basic principle that if the probability of each layer of defense (Dn) failing is Pn, then the probability of ten layers of defense (D1, D2, D3, ...D10) failing is P1 x P2 x P3 ... x P10. If each is so poor it fails one half of the time, each P is .5, and the combination of all ten will fail with a probability of .5 to the 10th power. That reduces it to .00098, or 0.098% -- about one in one thousand times. Every layer of cheese has a multiplier effect, even if it has lots of holes!

[Update 7/25/21:] Not out of the woods yet!

These two reports in the NY Times underline the need for continuing situational awareness, and guidance on that:
[Update 7/30/21:] Being smart requires better data and guidance

It’s situational awareness, stupid! Excellent NYT essay, If We Must Wear Masks Again, We Need a SmartApproach, underlines the need for better data and guidance to enable situational awareness -- and that the situation is constantly evolving.

All levels of government and institutions need to cooperate to teach each of us how to understand and apply the data and the science as it evolves -- to manage our own OODA loops. That means day by day, zipcode by zipcode, site by site, personal condition by personal condition. The CDC should teach us that its guidance is always contingent on the situation, and thus will change. 


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