Covid-19 Points of Leverage, Travel Bans and Eradication

Covid-19 has become a major topic for discussion with talk about many different interventions and ideas that might help, from 3-D printing parts for respirators to drafting medical students into hospitals to thorough hand-washing procedures.

However as rationalists we should be asking which actions have the highest expected utility, not which actions have some positive utility. In an exponentially growing process, the actions with the highest expected utility are those actions which intervene early in the process, and actions like drafting medical students which intervene late in the process when the disease has already grown to a huge size are “nice to have” but by that point most of the damage has been done.

Proper and Prompt Travel Bans do Work

As early as January 26th, I called for cancellation of flights to limit the spread of covid-19; there was some pushback based on the idea that travel restrictions don’t work which upon closer examination was actually the idea that late or half-hearted travel restrictions don’t work:

During the height of the SARS outbreak in 2003, he had a colleague who wanted to return to the UK from Toronto, one of the cities most affected by the virus. So she caught a domestic flight from Toronto to Vancouver, then boarded a flight to London. “When she arrived at Heathrow [airport] and authorities asked her, ‘Have you been to Toronto,’ she said no and walked right through.”

A policy that allows people to travel from an infected area to to an uninfected area is not a travel ban. It’s containment theater. A real travel ban would be grounding all international flights and stopping passenger trains and boats until the disease had been eradicated or at least very well contained, as well as aggressively tracking down and contact tracing people who slipped through before the lockdown, for example using cellphone data from intelligence agencies. A key point here is that mopping up a small number of cases that slip through is in fact possible.

It would have been expensive to do all this, but the cost of not doing it is that the developed world is now on lockdown, the stock markets have fallen by around 33% and we have about 10,000 deaths at the time of writing. And we have ended up implementing the travel bans anyway!


The optimal strategy to defeat the disease is currently the subject of much debate. Several strategies have emerged, and a popular meme right now is #flattenthecurve. The idea of flattening the curve is that if we increase the duration of the pandemic, the number of people infected at any one time will be lower and our ability to treat people properly will be increased. People put a lot of time into creating convincing memes and diagrams showing how this works:

Unfortunately people didn’t put much effort into getting the numbers right. Every single one of these diagrams is a steaming pile of nonsense because the line for “Healthcare System Capacity” is about 20-50 times too high, which was first pointed out by Joshua Bach. That tiny red line right next to the x-axis is our health system capacity:

(taken from The Imperial College COVID-19 Response Team’s latest report ).

The UK government’s “herd immunity” strategy was another possible way forward, but the government reversed course on this when they realized it would involve at least a few hundred thousand deaths.

Contain and Eradicate

In my opinion, the correct strategy to beat covid-19 whilst minimizing losses from this point forward is a contain-and-eradicate strategy. The New England Complex Systems Institute’s writeup on this, written by Nassim Nicholas Taleb of Black Swan fame outlines the strategy:

Since lockdowns result in exponentially decreasing numbers of cases, a comparatively short amount of time can be sufficient to achieve pathogen extinction, after which relaxing restrictions can be done without resurgence. …
Finally, the use of geographic boundaries and travel restrictions allows for effective and comparatively low cost imposition and relaxation of interventions. Such a multi-scale approach accelerates response efforts, reduces social impacts, allows for relaxing restrictions in areas earlier that are less affected, enables uninfected areas to assist in response in the ares that are infected, and is a much more practical and effective way to stop otherwise devastating outbreaks. …
A few other issues are of importance: They ignore the possibility of superspreader events in gatherings by not including the fat tail distribution of contagion in their model. This leads them to deny the importance of banning them, which has been shown to be incorrect, including in South Korea. Cutting the fat tail of the infection distribution is critical to reducing R0.


- Close borders and limit internal travel, lockdown and hygiene to drive R0 below 1

- Ban large events to cut off the long tail of the R0 distribution

- Use aggressive testing and contact tracing to clean up any remaining holdouts, and eradicate the virus on a region-by-region and country-by-country level.

- “Green” regions can return to mostly normal life, albeit without large events and travel. That means that people can go back to work and we can reverse the economic damage.

Contain-and-eradicate probably results in both less loss of life and less economic damage than any other strategy, and we can see this as a consequence of taking an exponential process and fighting it in the low orders of magnitude rather than the high ones. Flatten-The-Curve is bad because a flat curve that lasts for a long time is still, in log-terms, almost at the maximum power of the virus and therefore it can do huge amounts of damage. Herd-Immunity and Deliberate-Infection are bad for the same reason. The only other sensible plan I have seen is the idea of rushing a vaccine as quickly as possible, but that is beyond my expertise.

Travel bans and restrictions during a pandemic

Why do borders need to be closed now when the virus is already everywhere? Because there is still uncertainty about where the virus is and in what numbers. The virus wins when people with different amounts of virus mix, because areas of high virus can spread to areas of low virus whilst the reverse process doesn’t work.

Similarly, if you were certain about who had the virus, this would almost be trivial because all the infected could be moved to containment facilities and everyone else could get on with running the economy.

The virus wants to maximize entropy (virus spread everywhere), humanity wants to minimize it (all virus in one place), for a given total amount of virus.

The need for borders is a result of this combination of uncertainty and mixing being bad. And as Taleb points out in the NECSI review, travel bans and restrictions during a pandemic should be multilevel.

As we approach the “endgame” where testing is ubiquitous and virus numbers get closer to 0, borders become more important, because adding 500 cases to an area with 1 case is much worse than adding 2000 cases to an area with 1000 cases (you have to think in logarithms).

Though even when numbers are high, closing borders is still useful and we should still do it; principally because the decision to close can lag behind rapidly developing facts on the ground, or worse the decision to close borders to a particular area could leak, at which point people start actively helping the virus to spread as they flee from the soon-to-be locked down area. Of course nobody would be stupid enough to leak that information, right?

What if we do Mitigation instead?

If we do go down the mitigation path—letting most people get the disease—there are some important “dice rolls” that will determine how it goes:

  • The rate of long-term complications amongst covid-19 survivors,

  • The rate at which young & otherwise healthy people die when hospital treatment is denied due to overcrowding

  • Whether new pharmaceuticals like Chloroquine and Remdesivir are both effective and scalable, and how quickly covid-19 evolves resistance to them

  • Whether summer weather substantially slows the spread

  • Whether covid-19 picks up a mutation that makes it less lethal, or more lethal

A Test of Rationality

When competent Muggles make decisions, they’re usually very empirical about it. They build a chair with one leg, it falls over, and then they don’t do that again.

Covid-19′s exponential dynamics, asymptomatic carriers and long lag time between infection and death punished the try-it-and-see approach very hard.

By the time it became absolutely obvious to people who build one-legged chairs that this was a big deal and needed attention, the virus had increased both its numbers and distribution most of the way to its goal of infecting every human being on the planet.

Covid-19 was a rationality test as well as a competence test. China failed on rationality but passed on competence. The West failed hard on rationality and is on course for a F+ on competence as well. Vox and the other mainstream media who either mocked those who took it seriously early, or got on a soapbox talking about racism (which is bad, but was not even remotely the most important thing at that time) should take a reputational hit. The various government agencies that dithered throughout February should be investigated, particularly in the USA.