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  • - [Narrator] The goal of this video

  • is to help us all estimate

  • the actual new COVID-19 cases per day in your area.

  • And it's based on analysis by Thomas Pueyo,

  • he wrote an incredible blog post on Medium.

  • This is the link and I'll also include it

  • in the description below.

  • This is the data that he uses to do some of his analysis.

  • Now, some of you might be thinking,

  • I know the number of COVID cases in my area,

  • they're reporting it on the news every day.

  • But that's the reported number of cases

  • and that's based on the people

  • that happened to get the test.

  • There are a lot of people who might not have symptoms yet

  • or their symptoms are not severe enough to get the test yet.

  • So the actual cases are likely far larger

  • than the number of confirmed cases.

  • And we can see that in graphical form.

  • Once again, this is a diagram put together by Thomas Pueyo.

  • It's a screenshot from his blog post

  • which once again could be found here.

  • This is all his analysis, or based off of his analysis,

  • but this shows you what was happening in Hubei Province,

  • which is the province where Wuhan is.

  • And there's several interesting things here.

  • The vertical axis is the number of cases

  • and what we see on the horizontal axis is per day.

  • And so for example, we could pick January 23.

  • The yellow bar tells us the number of confirmed new cases

  • that day.

  • So these are people who would have been tested

  • and then they tested positive,

  • and it looks like that number is about 300.

  • But then we have this gray bar.

  • This gray bar is the actual number of new cases that day,

  • which is close to 2,500.

  • So roughly eight times as high.

  • Now you might be saying,

  • how did they know the actual number of cases

  • if they didn't test everyone?

  • Well, the way they did that is

  • when someone tested positive, they asked them,

  • when did you first get the symptoms?

  • And if they said, Hey, I first got the symptoms 10 days ago,

  • they would be included as a true new case.

  • An actual new case 10 days before that on January 13,

  • so that Chinese officials were able

  • to actually make these gray bars in hindsight,

  • based on when people said they first got the symptoms.

  • And there's a lot of really interesting information here.

  • First of all, we can see that Wuhan

  • was shut down on January 23.

  • So let's draw a line between the pre shut down

  • and post shut down.

  • And you can see just as the city officials

  • were starting to see confirmed cases,

  • the actual cases were far higher,

  • but then they shut down the city

  • essentially significantly slowing down the spread rate.

  • And a few days later, the actual cases

  • which were they were able to calculate in hindsight,

  • start to flatten out and then go down.

  • But even though they were going down,

  • the confirmed new cases continued to go up

  • because there is a delay.

  • You can even see the delay right over here.

  • And that is roughly the amount of time

  • between when people show symptoms

  • and they are actually tested.

  • Now you might be saying, all right, this isn't too bad.

  • It looks like things eventually became okay for Wuhan.

  • But this is because they did a very serious shut down.

  • If they did not do this shut down

  • and slow the spread of the virus,

  • you would have seen this exponential growth continue.

  • It's also worth remembering what I just drew this curve on.

  • This isn't the total number of cases.

  • This is the number of new cases per day.

  • If you want the total number of cases

  • at a given point in time,

  • you would have to sum up the gray or the yellow bars

  • depending on whether you want to look

  • at actual or confirmed cases.

  • So as of January 22, if you total up

  • all of these gray bars over here, as of January 22,

  • you get approximately 12,000 cases,

  • while if you add up all of the yellow bars,

  • that is roughly only 444 confirmed cases.

  • So before the city even went into shutdown,

  • and this is what the Chinese doing reasonably good testing,

  • you had a far higher number of cases

  • than the confirmed cases would make you believe.

  • And as large as the ratio is on a given day

  • before the city shut down,

  • between the number of actual new cases per day

  • and the number of confirmed new cases per day,

  • it's probably higher

  • in a lot of the geographies where we live,

  • because we're not testing as well as the Chinese did.

  • For example.

  • This is data once again compiled by Thomas Pueyo

  • on his blog post.

  • This is just a screen capture of it

  • and I'm really just giving his analysis.

  • This shows the total test performed,

  • and the tests performed per million citizens as of March 3,

  • and you can see for example,

  • where I live the United States is not doing so well.

  • And so the number of reported cases

  • in places like the United States

  • where we are really just starting to ramp up testing

  • is far understating the number of actual cases out there.

  • So how do we go about estimating

  • the actual number of cases in our area?

  • Well, once again, I'm going to use Thomas's analysis,

  • we're gonna be looking at the number of deaths

  • and estimations of mortality rate,

  • time from infection to death,

  • and how fast the virus actually spreads.

  • So in other videos, I'll talk more about

  • some of Thomas's analysis.

  • But for mortality rate, it'll make the math simple.

  • And this actually does seem to be a pretty good estimate,

  • we can assume that there's a 1% mortality rate,

  • the reports are as low as point 0.6% in South Korea,

  • and then as high as roughly 5% in places like Iran.

  • But it looks like the higher numbers

  • are where the hospital system is being overwhelmed.

  • And then the lower numbers at the 0.6%,

  • might not be fully accounting for all of the mortality

  • that will happen due to the cases

  • that are actually out there.

  • So we'll assume a mortality rate of 1%.

  • The other thing we need to think about

  • is the time from infection to death in those 1% of cases

  • where someone does die.

  • And to figure that out,

  • I will look at this data right over here.

  • This top chart, and it comes from this link,

  • which Thomas cites.

  • And I'll give the link in the description below.

  • This is the incubation period.

  • This is an estimate of the time

  • from when someone gets infected

  • to when they start to show symptoms.

  • And this estimate is roughly five days.

  • And then once you see symptoms,

  • how long does it take to death in those 1% of cases,

  • or whatever the percentage is?

  • Well, there's varying estimates,

  • but it looks like to make the numbers easy,

  • we can estimate roughly 15 days.

  • So one way to think about it

  • is five days from infection to showing the symptoms,

  • and then another 15 days from showing the symptoms to death

  • for a total of 20 days from infection to death,

  • in what we're assuming the 1% of cases.

  • So I'll write 20 days.

  • And now the other thing we're gonna estimate

  • is the days to doubling,

  • days to double.

  • This is how long does it take for the infection

  • to double in the population.

  • And this is gonna be heavily dependent

  • on what the population is doing,

  • how dense they are, how much they're interacting.

  • But we'll look at some of these estimates.

  • And they're in very different contexts.

  • And the lower the doubling rate,

  • that means a virus is spreading very fast.

  • While if you have a population

  • that's doing all the right things,

  • they're taking all the precaution,

  • the doubling rate will be lower.

  • So we could look at a conservative estimate

  • and take a higher doubling rate than all of these estimates,

  • it'll make our math a little bit easier.

  • Let's just assume a doubling rate of five days

  • and I'm using slightly different numbers than Thomas used,

  • but it will be indicative

  • and you can do the same analysis

  • with whatever estimates that you choose to do.

  • So let's assume five days to double,

  • which might be conservative,

  • especially for places like the United States

  • where we have not taken anywhere near the action

  • of a place like China or South Korea, or Japan.

  • So now let's use these numbers

  • to figure out what might actually be happening in our areas

  • based on the data that we are presented with.

  • So let's say that we unfortunately here on some day,

  • that there is one death in our region or in our city.

  • Now, based on our estimates,

  • we're saying that the average time from infection to death

  • is about 20 days.

  • That means that that person

  • would have likely contracted the virus roughly 20 days ago,

  • 20 days ago.

  • And so I'm gonna make a timeline.

  • This is 20 days ago, this would be 10 days ago,

  • 10 days ago, this would be 15 days ago,

  • and then this would be five days ago.

  • Now it's possible that they were the only person

  • who contracted the virus on that day,

  • and then they happen to unfortunately get very sick

  • and then pass away 20 days later.

  • But if we assume that the mortality rate is roughly correct,

  • it's quite possible that 100 people were infected that day.

  • The person that we know about is that one in 100

  • who actually gets sick enough to pass away.

  • And so if we assume that on 20 days ago

  • that not one person, but 100 people.

  • So the actual number of people who are infected that day

  • is 100 infected that day.

  • Once again, because it's a 1% mortality rate.

  • If we assumed a 0.5% mortality rate,

  • then we would say, all right,

  • there might have been 200 people infected that day,

  • 0.5% of whom get all the way to death 20 days later.

  • If you assume a 5% mortality rate,

  • which would be a very unfortunate situation,

  • but that is a mortality rate that we are seeing

  • in different parts of the world,

  • then you would have say,

  • well, maybe there were 20 people infected that day.

  • When you only have one or two or three deaths in a region

  • that will make the estimates more difficult.

  • But as unfortunately,

  • we are likely to see a larger number of deaths

  • in various regions

  • that will make this these backward estimates

  • more and more reasonable.

  • Now if the infection rate in the population doubles

  • every five days, what is now going to happen?

  • After five days, you're going to have 200 cases

  • in your region, 200 cases.

  • Now, these wouldn't just be new cases,

  • this would be the cumulative total number of cases

  • due to those hundred.

  • Now, this is actually quite conservative,

  • because this is assuming that those 100

  • that were infected 20 days ago

  • are the only infected cases in your region.

  • There might be other infected cases

  • that were infected before that date.

  • But I'm just assuming that the hundred

  • that were infected that day are the only cases

  • to be conservative, and so they double after five days,

  • and then they'll double again after five more days.

  • And so you will get to 400 cases

  • after five more days.

  • And then you will, after five more days,

  • you will have doubled and I can't even fit it

  • on the screen anymore.

  • You're going to have 800 cases

  • and then that means today just by evidence

  • of that one death,

  • you probably have on the order of

  • and I can't even draw the whole bar,

  • approximately 1,600 cases.

  • And so this is just to be a little bit sobering

  • about how serious this is,

  • and how much the data that we actually get

  • is actually lagging the circumstances on the ground,

  • particularly in places like the United States,

  • where we are barely even getting started testing.

  • For example, in my county,

  • which is Santa Clara County in California.

  • We just had our second death

  • unfortunately reported yesterday

  • and there was another death five days before that.

  • Now, there's only under 100 reported cases in my county,

  • but based on this analysis,

  • the actual number of infected persons in my county

  • is likely to be at least a factor of 10 more than that,

  • and it could be as high as 1,000, 2,000, 3,000 people.

  • We won't know for sure

  • until we can do the type of hindsight analysis

  • that the Chinese had,

  • but this is to just remind us how serious

  • the situation actually is.

  • So the big takeaway here

  • is to take all of this very seriously,

  • especially because the mortality rate itself can change

  • depending on how well equipped

  • the hospital system can handle the situation.

  • If we all socially isolate and take the proper precaution,

  • the spread rate will lower

  • and we won't overwhelm the hospital system.

  • And we'll hopefully be able to keep the mortality rate

  • as low as possible.

  • But if we don't take the precaution,

  • and if we're just complacent

  • because we see this lagging data

  • that's being reported to us because of the lack of testing

  • in places like the United States,

  • then it's very possible

  • that we eventually overwhelm the hospital system

  • in the next few weeks,

  • which would cause the mortality rate to go higher.

- [Narrator] The goal of this video

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