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@@ -56,21 +56,23 @@
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What Happens Next?
- COVID-19 Futures, Explained With Playable Simulations
- by Marcel Salathé (epidemiologist) and Nicky Case (art/code)
- 🕐 28 min play/read
-
-
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-Note: Total cases (gray curve) does not stop at herd immunity, but overshoots it! And it does this exactly when current cases (pink curve) peaks. (This happens no matter how you change the settings – try it for yourself!)
+NOTE: Total cases does not stop at herd immunity, but overshoots it! And it crosses the threshold exactly when current cases peak. (This happens no matter how you change the settings – try it for yourself!)
This is because when there are more non-s than the herd immunity threshold, you get R < 1. And when R < 1, new cases stop growing: a peak.
@@ -170,7 +186,7 @@ the second-most important idea in Epidemiology 101:
This means: we do NOT need to catch all transmissions, or even nearly all transmissions, to stop COVID-19!
-It's a paradox. COVID-19 is extremely contagious, yet to contain it, we "only" need to stop more than 60% of infections. 60%?! If that was a school grade, that's a D-. But if R0 = 2.5, cutting that by 61% gives us R = 0.975, which is R < 1, virus is contained!12
+It's a paradox. COVID-19 is extremely contagious, yet to contain it, we "only" need to stop more than 60% of infections. 60%?! If that was a school grade, that's a D-. But if R0 = 2.5, cutting that by 61% gives us R = 0.975, which is R < 1, virus is contained! (exact formula:12)
@@ -194,7 +210,7 @@ the second-most important idea in Epidemiology 101:
Scenario 0: Do Absolutely Nothing
-Around 1 in 20 people infected with COVID-19 need to go to an ICU (Intensive Care Unit).13 In a rich country like the USA, there's 1 ICU per 3400 people.14 Therefore, the USA can handle 20 out of 3400 people being simultaneously infected – or, 0.6% of the population.
+Around 1 in 20 people infected with COVID-19 need to go to an ICU (Intensive Care Unit).13 In a rich country like the USA, there's 1 ICU bed per 3400 people.14 Therefore, the USA can handle 20 out of 3400 people being simultaneously infected – or, 0.6% of the population.
Even if we more than tripled that capacity to 2%, here's what would've happened if we did absolutely nothing:
@@ -204,17 +220,18 @@ the second-most important idea in Epidemiology 101:
Not good.
-That's what the March 16 Imperial College report found: do nothing, and we run out of ICUs with 80%+ of the population infected.
+That's what the March 16 Imperial College report found: do nothing, and we run out of ICUs, with more than 80% of the population getting infected.
+(remember: total cases overshoots herd immunity)
Even if only 0.5% of infected die – a generous assumption when there's no more ICUs – in a large country like the US, with 300 million people, 0.5% of 80% of 300 million = still 1.2 million dead... IF we did nothing.
-(Lots of news & social media reported "80%+ will be infected" without "IF WE DO NOTHING". Fear was channelled into clicks, not understanding. Sigh.)
+(Lots of news & social media reported "80% will be infected" without "IF WE DO NOTHING". Fear was channelled into clicks, not understanding. Sigh.)
Scenario 1: Flatten The Curve / Herd Immunity
The "Flatten The Curve" plan was touted by every public health organization, while the United Kingdom's original "herd immunity" plan was universally booed. They were the same plan. The UK just communicated theirs poorly.15
-Both plans, though, are horribly flawed.
+Both plans, though, had a literally fatal flaw.
First, let's look at the two main ways to "flatten the curve": handwashing & physical distancing.
@@ -235,13 +252,15 @@ the second-most important idea in Epidemiology 101:
Three notes:
-This reduces total cases! Lots of folks think "Flatten The Curve" spread outs cases without reducing the total. This is impossible in any Epidemiology 101 model. But because the news reported "80%+ will be infected" as inevitable, folks thought total cases will be the same no matter what. Sigh.
Due to the extra interventions, current cases (pink curve) peaks before herd immunity is reached. And in fact, total cases doesn't overshoot, but goes to herd immunity – the UK's plan! At that point, R < 1, you can let go of all other interventions, and COVID-19 stays contained! Well, except for one problem...
This reduces total cases! Even if you don't get R < 1, reducing R still saves lives, by reducing the 'overshoot' above herd immunity. Lots of folks think "Flatten The Curve" spreads out cases without reducing the total. This is impossible in any Epidemiology 101 model. But because the news reported "80%+ will be infected" as inevitable, folks thought total cases will be the same no matter what. Sigh.
Due to the extra interventions, current cases peak before herd immunity is reached. In fact, in this simulation, total cases only overshoots a tiny bit above herd immunity – the UK's plan! At that point, R < 1, you can let go of all other interventions, and COVID-19 stays contained! Well, except for one problem...
You still run out of ICUs. For several months. (and remember, we already tripled ICUs for these simulations)
That was the other finding of the March 16 Imperial College report, which convinced the UK to abandon its original plan. Any attempt at mitigation (reduce R, but R > 1) will fail. The only way out is suppression (reduce R so that R < 1).
+// TODO: pic difference
+
That is, don't merely "flatten" the curve, crush the curve. For example, with a...
Scenario 2: Months-Long Lockdown
@@ -262,7 +281,7 @@ the second-most important idea in Epidemiology 101:
Scenario 3: Intermittent Lockdown
-This solution was first suggested by the Imperial College report, and later again by a Harvard paper19.
+This solution was first suggested by the March 16 Imperial College report, and later again by a Harvard paper19.
Here's a simulation: (After playing the "recorded scenario", you can try simulating your own lockdown schedule, by changing the sliders while the simulation is running! Remember you can pause & continue the sim, and change the simulation speed)
@@ -270,7 +289,7 @@ the second-most important idea in Epidemiology 101:
-This would keep cases below ICU capacity! We'd just need to... shut everything down for few months, open up for a few, shut down for a few, open up for a few... and repeat until a vaccine is available. (And if there's no vaccine, repeat until herd immunity is reached... in 2022.)
+This would keep cases below ICU capacity! And it's much better than an 18-month lockdown until a vaccine is available. We just need to... shut down for a few months, open up for a few months, and repeat until a vaccine is available. (And if there's no vaccine, repeat until herd immunity is reached... in 2022.)
Look, it's nice to draw a line saying "ICU capacity", but there's lots of important things we can't simulate here. Like:
@@ -304,31 +323,37 @@ the second-most important idea in Epidemiology 101:
-This is called contact tracing, and it's a core part of Taiwan & South Korea's successful strategies.
+This is called contact tracing. It's an old idea, was used at an unprecedented scale to contain Ebola23, and now it's core part of how Taiwan & South Korea are containing COVID-19!
-Traditionally, contact tracing is done with in-person interviews, but that's too slow for COVID-19's ~48 hour window. That's why on March 31st, an Oxford study recommended helping contact tracers with contact tracing apps.
+(It also lets us use our limited tests more efficiently, to find pre-symptomatic s without needing to test almost everyone.)
-Does that mean giving up privacy, giving in to Big Brother? Heck no! DP-3T, a team of epidemiologists & cryptographers (including one of us, Marcel Salathé) is already making a contact tracing app that reveals no info about your identity, location, who your contacts are, or even how many contacts you've had.
+Traditionally, contacts are found with in-person interviews, but those alone are too slow for COVID-19's ~48 hour window. That's why contact tracers need help, and be supported by – NOT replaced by – contact tracing apps.
+
+(This idea didn't come from "techies": using an app to fight COVID-19 was first proposed by a team of Oxford epidemiologists.)
+
+Wait, apps that trace who you've been in contact with?... Does that mean giving up privacy, giving in to Big Brother?
+
+Heck no! DP-3T, a team of epidemiologists & cryptographers (including one of us, Marcel Salathé) is already making a contact tracing app – with code available to the public – that reveals no info about your identity, location, who your contacts are, or even how many contacts you've had.
Here's how it works:
-(Here's the full comic, and here's a video adaptation by 3Blue1Brown)
+(& here's the full comic)
-Along with similar teams like TCN Protocol and MIT PACT, they've inspired Apple & Google to bake privacy-first contact tracing directly into Android/iOS. Next month, your local public health agency may ask you to download an app. If it's privacy-first & open-source, please do!
+Along with similar teams like TCN Protocol24 and MIT PACT25, they've inspired Apple & Google to bake privacy-first contact tracing directly into Android/iOS.26 (Don't trust Google/Apple? Good! The beauty of this system is it doesn't need trust!) Soon, your local public health agency may ask you to download an app. If it's privacy-first with publicly-available code, please do!
But what about folks without smartphones? Or infections through doorknobs? Or "true" asymptomatic cases? Contact tracing apps can't catch all transmissions... and that's okay! We don't need to catch all transmissions, just 60%+ to get R < 1.
-(rant about the confusion about pre-symptomatic vs. "true" asymptomatic:23)
+(Rant about the confusion about pre-symptomatic vs "true" asymptomatic. "True" asymptomatics are rare:27)
-Anyway, isolating cases would reduce R by up to 40%, and quarantining their contacts would reduce R by up to 50%24:
+Isolating symptomatic cases would reduce R by up to 40%, and quarantining their pre/a-symptomatic contacts would reduce R by up to 50%28:
-Thus, even without 100% contact quarantining, we can get R < 1 without a lockdown! Much better for our mental & financial health. (As for the cost to folks who have to self-isolate/quarantine, governments should support them – subsidized paid leave, job protection, etc. Still way cheaper than intermittent lockdown.)
+Thus, even without 100% contact quarantining, we can get R < 1 without a lockdown! Much better for our mental & financial health. (As for the cost to folks who have to self-isolate/quarantine, governments should support them – pay for the tests, job protection, subsidized paid leave, etc. Still way cheaper than intermittent lockdown.)
We then keep R < 1 until we have a vaccine, which turns susceptible s into immune s. Herd immunity, the right way:
@@ -336,6 +361,8 @@ the second-most important idea in Epidemiology 101:
+(Note: this calculator pretends the vaccines are 100% effective. Just remember that in reality, you'd have to compensate by vaccinating more than "herd immunity", to actually get herd immunity)
+
Okay, enough talk. Here's a simulation of:
@@ -363,35 +390,33 @@ the second-most important idea in Epidemiology 101:
What if R0 is way higher than we thought, and the above interventions, even with mild distancing, still aren't enough to get R < 1?
-If so, here's a few supplements:
+Remember, even if we can't get R < 1, reducing R still reduces the "overshoot" in total cases, thus saving lives. But still, R < 1 is the ideal, so here's a few other ways to reduce R:
Masks For All:
"Wait," you might ask, "I thought face masks don't stop you from getting sick?"
-You're right. Masks don't stop you from getting sick... they stop you from getting others sick.
+You're right. Masks don't stop you from getting sick29... they stop you from getting others sick.
-(sources for the comic: 25 26 27 28)
+To put a number on it: surgical masks on the sick person reduce cold & flu viruses in aerosols by 70%.30 Reducing transmissions by 70% would be as large an impact as a lockdown!
-Still, in science, one should only publish a finding if you're 95% sure of it. (...should.29) Admittedly, the current evidence for face masks on COVID-19 specifically, rather than "just" colds and flus, is less than "95% sure".
+However, we don't know for sure the impact of masks on COVID-19 specifically. In science, one should only publish a finding if you're 95% sure of it. (...should.31) Masks, as of May 1st 2020, are less than "95% sure".
-But, pandemics are like poker. Make bets only when you're 95% sure, and you'll lose everything at stake. We have to make cost/benefit analyses under uncertainty.30 Like so:
+However, pandemics are like poker. Make bets only when you're 95% sure, and you'll lose everything at stake. As a recent article on masks in the British Medical Journal notes,32 we have to make cost/benefit analyses under uncertainty. Like so:
Cost: If homemade cloth masks, same as the cost of all that soap for handwashing. If surgical masks, more expensive but still pretty cheap.
-Benefit: Even if it's a 50–50 chance of surgical masks reducing transmission by 0% or 70%31, the average "expected value" is still 35%, same as a half-lockdown! So let's guess-timate that surgical masks reduce R by up to 35%. (Again, you can challenge our assumptions by turning the sliders up/down)
+Benefit: Even if it's a 50–50 chance of surgical masks reducing transmission by 0% or 70%, the average "expected value" is still 35%, same as a half-lockdown! So let's guess-timate that surgical masks reduce R by up to 35%. (Again, you can challenge our assumptions by turning the sliders up/down)
-Here's a calculator of how masks reduce R! You can switch between cloth & surgical: (assumes cloth masks are half as effective as surgical masks32)
-
-[TODO: Actually allow toggling between cloth/surgical. Currently locked to cloth]
+Here's a calculator of how masks reduce R! You can switch between cloth & surgical: (assumes cloth masks are 2/3 as effective as surgical masks33)
-(other arguments for/against masks:33)
+(other arguments for/against masks:34)
Masks alone won't get R < 1. But if handwashing & "Test, Trace, Isolate" only gets us to R = 1.10, having just 2/3 of people wear cloth masks would tip that over to R < 1, virus contained!
@@ -399,9 +424,7 @@ the second-most important idea in Epidemiology 101:
Okay, this isn't an "intervention" we can control, but it will help! Some news outlets report that summer won't do anything to COVID-19. They're half right: summer won't get R < 1, but it will reduce R.
-For COVID-19, every extra 1° Celsius (2.2° Fahrenheit) makes R drop by 1.2%.34 The summer-winter difference in New York City is 15°C (60°F), so summer will make R drop by 18%.
-
-[TODO: Fix weird arrow glitch]
+For COVID-19, every extra 1° Celsius (2.2° Fahrenheit) makes R drop by 1.2%.35 The summer-winter difference in New York City is 15°C (60°F), so summer will make R drop by 18%.
@@ -427,15 +450,23 @@ the second-most important idea in Epidemiology 101:
-[TODO: Other options like temperature testing at malls, quarantines for travellers, replacing handshaking, etc]
+Not to mention all the other interventions we could do, to further push R down:
+
+
. . .
We hope these plans give you hope.
-Even under a pessimistic scenario, it is possible to beat COVID-19, while protecting our mental and financial health. Use the lockdown as a restart, keep R < 1 with privacy-protecting contract tracing, supplemented with at least cloth masks... and life can get back to a normal-ish!
+Even under a pessimistic scenario, it is possible to beat COVID-19, while protecting our mental and financial health. Use the lockdown as a "reset button", keep R < 1 with case isolation + privacy-protecting contract tracing + at least cloth masks for all... and life can get back to a normal-ish!
-Sure, your hands may be dry. But you'll get to invite a date out to a comics bookstore! You'll get to go out with friends to watch the latest Hollywood cash-grab. You'll get to people-watch at a library, taking joy in people going about the simple business of being alive.
+Sure, you may have dried-out hands. But you'll get to invite a date out to a comics bookstore! You'll get to go out with friends to watch the latest Hollywood cash-grab. You'll get to people-watch at a library, taking joy in people going about the simple business of being alive.
Even under the worst-case scenario... life perseveres.
@@ -451,16 +482,20 @@ the second-most important idea in Epidemiology 101:
...for how long?
-There's been reports of folks who test positive again after recovering, but those were false positives. Still, the possibility of waning immunity is very real. Either a new mutant strain evolves, or your immune system just... forgets.
+
+- COVID-19 is most closely related to SARS, which gave its survivors 2 years of immunity.36
+- The coronaviruses that cause "the" common cold give you 8 months of immunity.37
+- There's reports of folks recovering from COVID-19, then testing positive again, but it's unclear if these are false positives.38
+- One not-yet-peer-reviewed study on monkeys showed immunity to the COVID-19 coronavirus for at least 28 days.39
+
-The coronavirus responsible for COVID-19 is most closely related to the coronavirus responsible for SARS. SARS (probably) gave its survivors around 2 years of immunity.35 The coronaviruses that cause "the" common cold give you 1 year of immunity36. So:
+But for COVID-19 in humans, as of May 1st 2020, "how long" is the big unknown.
-What if COVID-19 immunity doesn't last?
-
-Here's a simulation starting with 100% , exponentially decaying into s after 10 days... but then back to susceptible, no-immunity s after 1 year:
+For these simulations, let's say it's 1 year.
+Here's a simulation starting with 100% , exponentially decaying into susceptible, no-immunity s after 1 year, on average:
-
+
Return of the exponential decay!
@@ -469,13 +504,13 @@ the second-most important idea in Epidemiology 101:
-Now let's simulate a COVID-19 outbreak, over 10 years, with no interventions... if immunity only lasts a year:
+Now, let's simulate a COVID-19 outbreak, over 10 years, with no interventions... if immunity only lasts a year:
-Previously, we only had one ICU-overwhelming spike. Now, we have several, and cases come to a rest permanently at ICU capacity. (Which, remember, we tripled for these simulations)
+In previous simulations, we only had one ICU-overwhelming spike. Now, we have several, and cases come to a rest permanently at ICU capacity. (Which, remember, we tripled for these simulations)
R = 1, it's endemic.
@@ -501,15 +536,15 @@ the second-most important idea in Epidemiology 101:
What if there's no vaccine for years? Or ever?
-To be clear: this is unlikely. Sure, there's never been a vaccine for any of the other coronaviruses before, but that's because SARS was eradicated quickly, and "the" common cold wasn't worth the investment. Coronaviruses aren't any more complex than the viruses we already have vaccines for, so most infectious disease researchers expect a vaccine in 1 to 2 years.
+To be clear: this is unlikely. Most epidemiologists expect a vaccine in 1 to 2 years. Sure, there's never been a vaccine for any of the other coronaviruses before, but that's because SARS was eradicated quickly, and "the" common cold wasn't worth the investment.
-Still, they've expressed worries about a vaccine: What if we can't make enough?37 What if we rush it, and it's not safe?38
+Still, infectious disease researchers have expressed worries: What if we can't make enough?40 What if we rush it, and it's not safe?41
Even in the nightmare "no-vaccine" scenario, we still have 3 ways out. From most to least terrible:
1) Do intermittent or loose R < 1 interventions, to reach "natural herd immunity". (Warning: this will result in many deaths & damaged lungs. And won't work if immunity doesn't last.)
-2) Do the R < 1 interventions forever. Contact tracing & wearing masks just becomes a new norm in the post-COVID-19 world, like how STI tests & wearing condoms became a new norm in the post-HIV world. (Nobody suggested "herd immunity" for HIV...)
+2) Do the R < 1 interventions forever. Contact tracing & wearing masks just becomes a new norm in the post-COVID-19 world, like how STI tests & wearing condoms became a new norm in the post-HIV world.
3) Do the R < 1 interventions until we develop treatments that make COVID-19 way, way less likely to need critical care. (Which we should be doing anyway!) Reducing ICU use by 10x is the same as increasing our ICU capacity by 10x:
@@ -527,8 +562,6 @@ the second-most important idea in Epidemiology 101:
Here's an (optional) Sandbox Mode, with everything available. Simulate & play around to your heart's content:
-[TODO: EMBED THIS IN A WAY THAT DOESN'T SUCK]
-
@@ -543,7 +576,7 @@ the second-most important idea in Epidemiology 101:
-Plane's in the ocean. We've scrambled onto the life rafts. It's time to find dry land.39
+Plane's sunk. We've scrambled onto the life rafts. It's time to find dry land.42
Teams of epidemiologists and policymakers (left, right, and multi-partisan) have come to a consensus on how to beat COVID-19, while protecting our lives and liberties.
@@ -563,166 +596,217 @@ the second-most important idea in Epidemiology 101:
The only thing to fear is the idea that the only thing to fear is fear itself.
-{ Please let me know what you think! How did it feel overall, any parts in particular that went too slow or were too confusing, factual inaccuracies, nuances I missed, stuff I oughta mention, etc. Thank you! }
+[ If you'd like, please give me feedback on the Patreon comments! Don't share this yet, it'll go live tomorrow May 1st noon Eastern time. Thank you so much! 💖 ]
