Ruminatin’ Re: Risk & Rattlers
Bob Runs the Numbers, Episode 6
People always tell me “oh go take a hike.” And I follow their well-intentioned advice, often sauntering through habitat that supports rattlesnakes and other venomous snakes.
This can be scary. Each year in the US, there are between 7000 and 8000 people bitten by venomous snakes. On average, about five of those people die.
It’s a risk I take; living life is a balancing act between risk and reward. And of course there are ways to mitigate risk. I don’t go skipping through the sagebrush barefoot. I wear boots and I watch where I step.
And I gotta say, nothin’ pumps up the adrenaline quite like seeing a Western Diamondback slither across the trail in front of you.
There’s another pretty obvious risk we’ve been dealing with over the last year and a half. Our lives have been (and still are) upended. Worse, many of us have lost people we love.
I can’t help myself: let’s compare these risks. Let’s think about the risk from Covid-19 and re-visualize it as the risk from a venomous snake bite.
It’s a chance to do some old-fashioned compare & contrast exercises, just like we did for essays in high school!
A difference that I won’t dwell on is the very conspicuous factor of tribalism, and how tightly “who did you vote for” and “how have you mitigated Covid-19” are correlated.
Jaw-droppingly astonishing, and mind-bendingly stupid.
As a random guy just watching the last eighteen months unfold, I’ve gotta say: this has been astonishing. Jaw-droppingly astonishing, and mind-bendingly stupid. But. I’m not going to deep-dive on this. I’ve resigned myself to the sad reality that we’ve all retreated to our partisan tribes and I don’t know how to solve that. This trap of tribalism might not even be solvable. 🙁 I mention it only so we can pretend that tribalism isn’t an issue in our thought experiment; what if we compare venomous snake bites and Covid-19 without a political lens? What if we just run the numbers and see what implications pop out?
Another difference is obvious. Very literally and specifically, obviousness. Venomous snakes are visible to the naked eye. Our primate brains have had hundreds or thousands of generations to train ourselves to stay out of reach of these “slimy” “disgusting” creatures. (OK, fine: they’re neither slimy nor disgusting. But our species has had eons to develop and pass on a fear of venomous snakes.) Germ theory is much more recent. Humanity has only had a couple hundred years to familiarize ourselves with the tools to grapple with health risks that we can’t see. And analyzing risk from unseen causes requires trust. And math. Math that has not been ingrained in our history back to our time on the Serengeti.
3. Covid-19 Is 20X Deadlier Than Snakebite
Another substantive difference: catching Covid-19 is much deadlier than receiving a venomous snakebite. Taking a broad look, the national venomous snakebite “case fatality rate” works out to 0.07% compared to Covid-19’s overall CFR of around 1.5%. That’s right: a randomly-picked person infected with Covid is over twenty times more likely to die than if they’re bitten by a venomous snake. (Due to the very age-dependent CFR for Covid-19, you can slice-n-dice the demographics to find subsets of the population where the risk “delta” is less than a factor of twenty. Someone of my age, sex, BMI, and blood pressure has a Covid-19 CFR that’s in the same ballpark as a venomous snakebite CFR. There are some demographic slices with Covid-19 CFRs even lower than a venomous snakebite CFR. Of course there are corresponding demographic slices with a risk much higher than the twenty-times top-line comparison.)
So. Overall, thinking about the risk of venomous snakebites dramatically undersells the Covid-19 threat … but if we’re doing comparisons we have to start somewhere.
4. That Exponential Growth Thing
A much more serious difference between the risk from venomous snakes and the risk from Covid-19 is that Covid-19 spreads. If I get bit by a rattlesnake, I won’t start suddenly throwing handfuls of rattlesnakes at the people living in my home, the office, or the grocery store. My suspicion is that throwing handfuls of rattlesnakes at loved ones and strangers would be frowned upon. Covid-19’s R0 (“R-naught”) of about 2.5 would correspond to throwing enough rattlesnakes at people that a couple of them get bit.
Our brains aren’t wired to deal with exponential growth.
If we’re thinking of the rattlesnake equivalent of the Delta variant with its much higher R0 value, you’d have to throw snakes at people until, say, seven of them get bit. Then, of course, each of those people would have to throw handfuls of rattlesnakes at people they cross paths with. And so on, and so on. Our brains aren’t wired to deal intuitively with the kind of exponential growth that Covid-19 forces us to acknowledge.
5. Unwitting Spread
Covid-19 has the insidious property that people can spread it without even knowing they have it. I can’t imagine getting a snakebite without knowing about it, but if a rattlesnake did secretly bite me, and I was unwittingly throwing handfuls of rattlesnakes at my friends, that would really be uncool of me and dangerous to everyone around me. People might forcibly stop me. I might even be arrested!
Back to Hiking
If you and I are on a hike and you’re about to step on a rattlesnake, be assured that I will yell at you and — if you’re close enough — I may even forcefully tug on your arm to keep you from risking being inadvertently bitten by a deadly snake. Even though a snakebite “only” has a 0.07% chance of killing you, my reaction would be to keep you away from envenomation.
This yelling — or, even more dramatically, physical restraint — isn’t a way for me to scold you or mock you or berate you. It’s to save your life.
And I hope you’d do the same for me.