It is merely enough to make the r0 after containment measures less than 1.
Then the problem will eventually go away.
As someone said, social distancing measures to work must be done when it seems to be overreacting.
And if they work, it will seem as if we overreacted.
(You ask an annoying, but fair and important question here. We shouldn't lose our skeptical mind.)
Social distancing, contact tracing and isolation of the sick work well, and that was almost certainly the critical portion of the response.
For example, this paper makes a solid argument that the travel ban delayed the epidemic across china by only a few days:
https://science.sciencemag.org/content/early/2020/03/05/scie...
- Lockdown in northern Italy: People ran to the south taking the virus with them. - Schools closing, folks asked to work from home in Madrid: Families drive to the coast where bars and restaurants are full.
I agree that in a place where compliance with social distance measures is high (I'm thinking South Korea, Japan), that would be enough. But that doesn't work everywhere.
You might get to the point where you need to make a choice between who you're going to accept in the hospital (younger people then get the fast lane over the elder due to potential higher amount of life years being saved). I believe its like that in Italy at this point.
If old people quarantine themselves the chances of them not getting this disease increase. I know a few elder (including loved ones) who I don't want to see passing away, so I have an interest in this.
On a different note, I also find it selfish and distasteful to feel careless about big groups of other people based on discriminatory elements such as age.
And that's not even addressing that the at-risk group isn't just the old.
https://pbs.twimg.com/media/ES5U9YUXkAA1e7H?format=jpg&name=...
They boasted about buying now cheap tickets to fly on vacation instead of "suffering through" home office as ordered by our company.
These are educated people. Doesn't seem to save them from ignorance though, as they are on the "just a flu" train.
Also, the lower the R factor, the faster measures can be relaxed. With an R0, if you want to guarantee putting out everything, you need to hold the measures for the longest possible lifetime of the disease. ( what's that? A month?)
Assuming half the country gets infected and the 20-30% hospitalization rate remains that's 35 million or so patients.
So best case we can treat about 5% of the cases. And that's if we let no other patients into the ICU. Which isnt practical because they run at ~80% capacity or more anyways. So really that number drops down to more like 1%.
The only option is to contain it or watch millions die.