The WHO pins it at 0.7% and falling as understanding thereof and treatment improves [1 - page 12, graph on page 13]. This makes a lot of sense as the earliest numbers were based only on people presenting severe symptoms, and huge quantities of people with nCoV are completely and totally asymptomatic.

As with the flu, mortality is highest in older people, and the immunocompromised.

[1] https://www.who.int/docs/default-source/coronaviruse/who-chi...

Thank you for providing the source. This helps tremendously in clarifying and advancing the discussion.

We need to be careful about what exactly the WHO is reporting. In this case, they are reporting estimates of the crude fatality rate defined as deaths / total cases. This will equal the mortality rate once the outbreak is over, but has limited use during the outbreak as they call out in footnote:

> The Joint Mission acknowledges the known challenges and biases of reporting crude CFR early in an epidemic.

During the outbreak, a better but still imperfect estimate is deaths / settled cases where settled cases is the sum of deaths and recoveries. [1]

[1]: https://news.ycombinator.com/item?id=22399755

Indeed, I am basing my confidence on the trendline in the graph on page 13. The number of people infected (41K) is about two thirds now as compared to the peak (58K), and the CFR is dropping exponentially as cases resolve.

The situation outside of Hubei looks encouraging but the data appears to indicate that there is probably a threshold of patients (different for each country) from which the mortality starts to rise.

Reasons behind this might be either institutional or purely statistical that is it might be possible that each country can keep alive at least certain number of critical patients and starts to fail when certain number is exceeded and it is possible that smaller number of patients are not representative enough and do not contain high risk patients (elderly, people with other chronic illness etc).

Edit: Diamond Princess is not representative because people have been evacuated and are now counted under countries statistics https://www.bloomberg.com/news/articles/2020-03-01/man-dies-...

Like you say, if you are over 70 and get it, your mortality rate would be more like 10%, even with these lower numbers.

> This makes a lot of sense as the earliest numbers were based only on people presenting severe symptoms, and huge quantities of people with nCoV are completely and totally asymptomatic.

Isn't another possible explanation that it simply takes very sick people a few weeks to die from it, so if you start counting a week farther back then the confirmed-then-died rate will be higher? (Due to undercounting of people who are going to die from it but haven't yet.)

For comparison, the H1N1 influenza (the most common subtype in 2009) had a fatality rate of 0.45%. In the elderly (65+) studies shown it had a case fatality rate of up to 10% [1].

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3809029/

WHO wants to have their cake and eat it too. They designate Covid-19 as the severe disease, and want only those numbers confirmed with tests. Then to calculate death rate they look at everyone who is infected with novel coronavirus, including those that have not recovered yet.

> huge quantities of people with nCoV are completely and totally asymptomatic.

From 72.314 cases, as of February 11, 2020, only 889 asymptomatic cases (1%).

https://jamanetwork.com/journals/jama/fullarticle/2762130

Well, if they're asymptomatic they don't seek treatment right? So how would you catch them, except incidentally to incidents like the cruise ships.

> However, the total number of COVID-19 cases is likely higher due to inherent difficulties in identifying and counting mild and asymptomatic cases.

> Nevertheless, all CFRs still need to be interpreted with caution and more research is required.

Like the cruise ships:

> The ministry has tested 4,061 people so far, of which 705 were positive, including 392 people who were asymptomatic.

So seems your estimate of "huge numbers of asymptomatic" is not far from the mark. Apologies. See also:

> Asymptomatic infection has been reported, but the majority of the relatively rare cases who are asymptomatic on the date of identification/report [due to contact testing] went on to develop disease. The proportion of truly asymptomatic infections is unclear but appears to be relatively rare and does not appear to be a major driver of transmission.

https://www.who.int/docs/default-source/coronaviruse/who-chi...

From same report: "6.1% [of infected] are critical (respiratory failure, septic shock, and/or multiple organ dysfunction/failure)." This does not look like the kind of thing you can treat DIY style.

"Early estimates place it far higher than 0.7%" seems both incorrect and a bit alarmist.

From what I've read (see below), the current consensus is that China is under-reporting total infected, possibly by an order of magnitude. China also made several missteps in their initial and ongoing response that is likely increasing their mortality rate, especially in Wuhan and surrounding Hubei. Worldwide, there certainly are and will be people who are infected but are asymptomatic, and don't even know (and of course aren't being counted at all).

I would expect that the mortality rate outside China is -- and will stay -- sub-1%, unless it mutates and becomes more deadly, or if health services eventually become overwhelmed due to quick spread. Analysis of primary data seems to indicate that even non-Hubei China has a mortality rate around 0.7%; Hubei's mortality rate is skewing the total upward by a lot. Rest-of-world looks to be around 0.6% so far.

https://www.cnn.com/2020/02/19/health/coronavirus-china-sars...

https://www.bmj.com/content/368/bmj.m606

https://github.com/CSSEGISandData/COVID-19 (primary data, which links to some analysis and visualizations)

It looks to me that there is probably a threshold of patients (different for each country) from which the mortality starts to rise.

Reasons behind this might be either institutional or purely statistical that is it might be possible that each country can keep alive at least certain number of critical patients and starts to fail when certain number is exceeded and it is possible that smaller number of patients are not representative enough and do not contain high risk patients (elderly, people with other chronic illness etc).

If you look at the recent data then when number of patients approaches 100 then mortality (CFR) exceeds 2%. Only exception seems to be South-Korea. Diamond Princess is not representative because patients are now evacuated and counted under their countries statistics.