When you have a huge hole where your nation’s leadership should be, it is wise to borrow the best of other people’s leaders. They can’t make America’s big decisions, but they can fill in some of the gaps.

In the Covid-19 pandemic, we can take comfort in their competence and use their wisdom to guide us about what we each should do.

Right now, the United States and many other nations are considering easing social distancing and other restrictions if and when their new coronavirus cases and hospitalizations become flat or start to fall. And German Chancellor Angela Merkel (who happens to have scientific chops) has an important lesson that we should all listen to.

On Wednesday, she laid out important logic about the coronavirus pandemic that hasn’t been communicated clearly enough here in the US. In simple and clear terms, she explains why Germany doesn’t have much “wiggle room” in its hospital capacity. Because of this, any lifting of its lockdown, like allowing some shops to open next week, will remain “on thin ice.”

Merkel’s explanation, which went viral, is centered on the metric called R0, or basic reproduction number. It represents the number of people a sick person will infect on average in a group that’s susceptible to the disease (meaning they don’t already have immunity).

She says that if Germany’s R0 were to shift from a flat rate of 1.0 to 1.1, the nation’s hospitals would be crushed by October, without sufficient resources to care for all of the severely ill Covid-19 patients. If the R0 goes up to 1.2, that overload hits in July. And so on.

Related Why France has 4 times as many coronavirus deaths as Germany

Covid’s current global average R0 is 2-2.5, but Germany has done a good enough job of managing its outbreak to get its reported estimated R0 down to 0.7 as of April 17. That’s low enough for Merkel to sanction “a tentative easing of restriction.”

Germany is not out of the woods, however. Marieke Degen, the deputy spokesperson of Germany’s Robert Koch Institute, told Vox’s Alex Ward that it’s “very important to stress that Germany is still at the beginning of the epidemic” and that more and more elderly people in the country are getting sick.

America, for many reasons, has even less wiggle room than Germany. Germany has eight hospital beds per capita compared to America’s 2.7 beds. In ICU beds, Germany has 8.3 per capita while America has 6.6.

It is also testing for coronavirus at twice the US rate (21 vs 9.8 tests per 1,000 people). Without robust testing, you can’t keep good tabs on R0 or the related Rt — and you can end up flying blind, risking health system overload and avoidable deaths.

Here's Instagram co-founder @kevin's new virus site that takes his recent models and updates them live in real time, in collaboration with @mikeyk — https://t.co/zpi35TIEdw pic.twitter.com/2qHZLDaL5n — Emily Chang (@emilychangtv) April 17, 2020

Covid-19 spreads in an exponential way, and it’s worth emphasizing exponential growth’s dynamics. Tiny shifts in risk grow very quickly, leading to deadly results, as this useful tweet thread shows:

Exponentials still have the capacity to shock me.



If mass wearing of masks make just 0.01 shift in the spread per day, from say 1.22x to 1.21x, there would now be ~20% fewer cases (and ~20% fewer deaths) in the UK since March 12.



I had to double check that multiple times. — Do

Syme (@dsymetweets) April 5, 2020

The small choices we each make about risky behaviors are like playing Russian roulette, but with a machine gun. You may have thought that if you’re not in a high-risk group (like older adults), and the case fatality rate is around 1 percent, then the threat isn’t so great. Surely we can loosen restrictions?

But that’s like being locked in a room with 100 people, where your collective behavior determines how many bullets are live in the machine gun that’s about to strafe all of you. You might not die, but others surely will.

Covid-19 is already the leading cause of death in many areas, including New York state, Louisiana, and Washington, DC. Do you want to add ammunition to its arsenal?

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