Most recent JAMA article 20% Chinese cases severe or critical
https://jamanetwork.com/journals/jama/fullarticle/2762130Covid 19 is largely unknown and as the world has no immunity could infect almost everyone. The infection rate is estimated a two cases per contact, a bit less than regular flu, but far less than measles, so it may be slow moving but persistent.
The mortality rate seems to be lower than H1N1 flu pandemic in 2009 ( see below) but we really dont know as we can't trust Chinese statistics and the current testing methods are a bit suspect. It is unlikely the 11% seen in the H1N1 study quoted below, and I can't imagine the Chinese could have covered up 20% of 80,000 people dying but who knows. Per the JAMA article they claim overall mortality of 2.3% and 1
5% over 80 yo, far higher than usual flu ( less than 1% even in elderly)
"During the study period there were 1088 cases of hospitalization or death due to pandemic 2009 influenza A(H1N1) infection reported in California. The median age was 27 years (range,<1-92 years) and 68% (741/1088) had risk factors for seasonal influenza complications. 31% (340/1088) required intensive care. Rapid antigen tests were falsely negative in 34% (208/618) of cases evaluated. Secondary bacterial infection was identified in 4% (46/1088).
Overall fatality was 11% (118/1088) and was highest (18%-20%) in persons aged
50 years or older. The most common causes of death were viral pneumonia and acute respiratory distress syndrome"
What is not really known is the incubation period and if asymptomatic people are virus shredders and for how long.
While the 1918 pandemic deaths were largely due to pneumonia, as mentioned above, influenza frequently kills just by itself ( viral pneumonia and acute respiratory distress syndrome) especially in susceptible young people whose immune system goes into overdrive.
When we get data from more reliable countries like Italy and Korea we will have a better idea of the impact especially the hospitalization rate and mortality. This will be the human costs, but the economic costs will ( have already) include direct medical expenses, supply chain disruptions, people afraid to go out and travel and shop and go to work.
What I haven't heard much of is the fact that this could be far far worse. What if this thing had Ebola's mortality rate? There is probably a bat virus out there that does so we need to reevaluate our dependence on China, excessive foreign travel, cutting biological research funding etc etc.