Why would we only expect half the world to get it? My understanding is that everyone needs to be eventually exposed in one way or another, either contracting the virus or getting a vaccine (when they are ready).

Herd Immunity (https://en.wikipedia.org/wiki/Herd_immunity) means that everyone doesn't need to get it. The threshold for COVID-19 is estimated to be between 29-75%.

On a different note in scientific paper what is considered too large an error margin to consider it a value to talk about. If the above is true that makes it what 52%+- 23

Assume that everyone who has it spreads it to 2 people on average before dying or recovering. If one of the 2 people you would have spread it to is immune, you will only spread it to 1 person instead, and the total number of infected will not rise.

Huh? If you spread it to 1 person, then the total number of people who have been infected will rise by 1.

I mean the total number of people sick at any given time, not the total number of people who have ever been infected.

The parent poster asked "Why would we only expect half the world to get it?". It sounds like your answer to that is "no no, almost everybody will get it, they'll just get it at different times".

If the effective transmission rate is 1, yes, more people will get it, and then the effective rate will go below 1, and you enter exponential decay.

China claims to have stopped it in its tracks.

This is a 100% serious question: I see that your statement is simply stated (and it's a fair representation of what China is saying as of /right now/), but I get the feeling you either agree with it and are applauding China, or are pointing out how ludicrous / absurd such a position is.

For the tone-impaired amongst us, if you are taking one of the positions, can you please help this simpleton understand what you think of China's proclamation?

I ask because I really don't know what most people think these days about the news coming out of China.

Sincere thanks.

Personally, I take anything announced by the ccp with a grain of salt. They can maneuver the news any which way they want without being challenged internally.

Hong Kong announced ~48 new confirmed COVID-19 cases today [1] (within last 24hrs) with experts predicting 300-500 in the next two weeks. Unless HK (and Taiwan who also has seen spikes) is still not considered China?

We already know most test results are days late from the actual swabbing + ~5-10 days of being asymptomatic + showing early symptoms before ending up in a hospital to be tested. Making the results we see from HK's (free) press today are up to 2 weeks old already and China's second wave could have already started.

Either way mainland China faces a similar increase by the second-wave return of citizens as people return from visiting the rest of the world - a world increasingly being ravaged by COVID. Ignoring the global travel, HK<>mainland travel is super common and a good early signal for mainland.

I personally know lots of Chinese citizens who stayed in Canada after early results from China and are waiting it out here with family.

I highly doubt the Chinese authorities can rest until the virus is shutdown globally. We live in a global economy with China as the engine. If China returns to normal before that it won't be long until super-infectors return to some of the most densely populated cities on the planet and everyone is being told to self-isolate again.

If China does end self-isolation (or the far more authoritarian measures that aren't found elsewhere) early then they also better close their borders from inbound travelers and tell their returning citizens to stay where they are.

[1] https://www.scmp.com/news/hong-kong/health-environment/artic...

China locked down the entire country and implemented draconian never that we have (and will not). Check out what is required to travel right now in China:

https://twitter.com/CarolYujiaYin/status/1239583581325778944

Here in the USA we are only two days removed from having run Democratic primaries where millions of people lined up and crowded together in small rooms - the total opposite of what China (and South Korea and Japan) have done. Images of packed beaches and boardwalks continue to emerge. The unfortunate fact is that many Americans aren't taking this pandemic seriously which is going to result in a much worse time of it than it could have otherwise been.

China effectively let everyone catch the disease so that now everyone is either immune or dead.

This is wildly untrue and unfounded.

You think they handled a billion infections? Did you really think this through? The current numbers in China are ~80,000 not 1,000,000,000. Common sense should explain to you why that's not possible.

Which means the only winning strategy is resume our lives - not hide in our homes. Those who are in the vulnerable categories should absolutely shelter-in-place, but the rest of us need to earn a living.

The government cannot possibly bail out every single business in the nation.

TLDR: Everyone under 50- go to work, wash your hands, maybe get sick. Everyone over 50 - stay at home until there's a vaccine.

Except it doesn't work that way, because a certain % of people who get sick require hospitalization to survive - including people under 50 - even if that's a lower % than those who are older and/or have underlying medical conditions. We have under a million total hospital beds in the USA. If 100 million under 50s get sick right away and just 3% of them require hospitalization that's still 3x as many hospital beds as we have in the entire country (and that doesn't factor in all the people who require hospital beds for non-coronavirus reasons).

How many hundreds of thousands or millions of preventable deaths are acceptable to you for a faster bounceback of the economy?

> How many hundreds of thousands or millions of preventable deaths are acceptable to you for a faster bounceback of the economy?

This is a really good question, because a dead economy is deadly too, and a shutdown is particularly hard on the people who can afford it least.

Normal Quality-Adjusted-Year-of-Life estimates are $50,000-$150,000. If this is a good estimate then ideally our economic shutdown won't pay much more than that overall; if we pay much more as a society, we have probably gone too far.

(And of course it feels bad to put a dollar value on a human life, so not everyone will want to do that. This doesn't change that we have to make this decision, though, it just means that we make our decision blindly and harm people more than we ought.)