Yes and no. I'm not a doctor so an actual MD will step in here and correct me I'm sure. My understanding from reading both the CDC literature and the WHO literature is that there are two things, the SAR_nCOV2 virus which is out there spreading from host to host, and the COVID19 disease which is one manifestation of the virus in people.

If my understanding is correct, the answer is that not everyone who gets infected by the virus will develop the disease. That can happen for a number of reasons apparently including but not limited to, a small enough sample got your immune system going fast enough that you didn't develop the disease, or you have previously been exposed to something similar enough that your immune system got ahead of the virus, or during the course of the infection your lungs didn't get involved before the immune system had begun producing anti-bodies.

To explain the numbers, the fatality rate is a function of only those people who develop the disease. Your chance of developing the disease is a function of how strong your immune system is and so it develops more commonly in people with weak or otherwise compromised immune systems.

But take this as just one opinion based on reading the literature. It sounds to me as if it is similar to the difference between HIV and AIDS, where you can become infected with the HIV virus but not develop AIDS if that virus is kept minimized with anti-virals.

Here's the WHO drawing a pretty limited distinction, with one name being used for science and one for public communication:

https://www.who.int/emergencies/diseases/novel-coronavirus-2...

"COVID-19 is the disease, SARS-2-CoV is the virus." [1]

1. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX...

For instance, it says:

Estimates are ~80% of infections non-severe, including asymptomatic infection likely.

The language there doesn't separate the asymptomatic infections from the disease.

Therefore it feels like at this point their data would be pretty representative of what percentage of the cases are severe vs critical and what the death rate is (accounting for both the overwhelmed medical case in Wuhan and for the under control case in rest of China).

South Korea is also doing a pretty good job with testing to control the outbreak although they haven’t yet gotten it as under control as China does. So their numbers would be a good data point to cross-validate the China numbers.

In countries like Italy (or Wuhan early on) the number of confirmed cases wasn’t equal to total cases as evidenced by continued growth of the epidemic. So it’s reasonable in those cases to assume that more severe cases are being found and less severe ones are being missed.

https://twitter.com/MikeIsaac/status/1238604080571772928

I don't see why they would back off of the monitoring and fever clinics without some better measure in place (a vaccine or effective treatment or whatever). It's of course very likely there will be new cases. The likelihood of unchecked spreading seems much lower.

I think there's a decent chance the outcome won't be nearly as bad as the worst case scenario, but the worst case scenario is pretty scary. There is a non-zero probability that this wave is only beginning, that there are going to be future outbreaks and pandemic waves this year, and that by year's end there'll be millions of deaths globally.

Anyone with a fever is screened for the infection using a portable CT scanner (they don't do a full image, they take a couple slices).

People with suspect CT results are tested and held in quarantine until the test result comes in.

The virus simply will not spread as fast in those conditions as it did when local officials were covering up, and people can start moving around more without backing off those conditions.

The, e.g. “32 million cases of flu” reported by the CDC is not based on 32 million positive test results. It’s extrapolated based on a factor of how many cases require hospitalization, and how many people seek medical care, which itself is based on antibody and behavioral surveys.

> The numbers of influenza illnesses were estimated from hospitalizations based on how many illnesses there are for every hospitalization, which was measured previously (5).

> Some people with influenza will seek medical care, while others will not. CDC estimates the number of people who sought medical care for influenza using data from the 2010 Behavioral Risk Factor Surveillance Survey, which asked people whether they did or did not seek medical care for an influenza-like illness in the prior influenza season (6).

After reading more about it [1] you almost wonder how much better than a WAG (“Wild Ass Guess”) it really is.

Frankly I am finding this whole area of medical science entirely underwhelming relative to the potential impact to lives and economies of the world.

https://www.cdc.gov/flu/about/burden/how-cdc-estimates.htm

The problem is we don't have the same data for this virus yet.

There was also a statistical analysis of the Diamond Princess cases. That produced an estimate that about 17% of infections were asymptomatic. [1] It's possible that there are less asymptomatic cases among the older population, but between the Guangdong and the Diamond Princess data, I doubt it.

The 3.4% CFR that everyone is looking at is also dependent on some reasonably adequate level of medical care. If this thing blows up, most people are going to be on their own, and in the absence of a miracle drug that is widely available (maybe Chloroquine?), the fatality rate with home care I would expect to be something like 10-15%.

[1] https://www.eurosurveillance.org/content/10.2807/1560-7917.E...

That seems unlikely.

Testing capacity in lots of the world is extremely limited. The US is reserving test kits for the most sick/at risk; people at a low risk are unlikely to be tested.

It seems to me that the focus would be on testing alive people, and that we are subsequently undercounting deaths - at least, in these relatively early stages.

But as everybody points out, the correct number can only be claculated after the fact. and even the it might be of.

So long term a lower CFR seems to make sense.

The people who are dying are usually older, or have preexisting conditions and their deaths can easily be chalked to their age/condition.

"Is the death rate 0.5% or 5%？It depends on whether the hospital is overloaded. Let's take a look at the data."

I'm not sure where you're getting the 3% number from. If you read the New York Times maps page data[1] and just divide the total deaths by total cases you get 3.7%, but that isn't the death rate because it doesn't take in to account a lot of factors.

Instead, there's a good article[2] about how bad the virus will get, that says estimates put it in the range of 0.1% to 3%. (With the seasonal flu being somewhere around 0.1%, but the Spanish Flu of 1918 being somewhere around 3%.)

That said, the general intuition that less reporting of cases means that some part of the death rate is over-inflated makes sense. But also consider that there are factors that go in the other direction. Anyone who currently has the virus but has not recovered or died can be under-inflating that rate. And there are likely lots of other factors, which is why articles often mention that the "true" death rate cannot yet be calculated.

(Also the death rate varies a lot with age, and isn't the only factor in determining the "badness" of a virus. Which that second article goes into more depth on—things like how contagious it is, and how early a vaccine can be developed. So the average rate being half of the current numbers doesn't necessarily mean the concern is over-inflated as well.)

[1]: https://www.nytimes.com/interactive/2020/world/coronavirus-m...

[2]: https://www.nytimes.com/interactive/2020/world/asia/china-co...