It isn't the end of days, but we know South Korea has been testing like crazy and they are running a 3% death rate and they have both much better medical care than the US does and their numbers have been edging up. Oh, and they have a much younger populace who have been getting infected.
South Korea represents pretty much an absolutely best case scenario for any outbreak that is more than a few hundred people and represents a statistically valid scenario.
The US is averaging right now 38% deaths/(deaths+recovered). We know we are missing a lot of people who are probably infected, but even if it is a lot higher, it doesn't drive it down below 5%. Without sufficient medical care we do have it well characterized for asymptomatic (about .25%), symptomatic mild (about 50% of cases), symptomatic moderate (about 20% of cases), severe (about 14% of cases) and critical (about 6% of cases).
Without hospital level care most of the severe and critical cases will die. Even with intensive care the WHO estimate is 3.4% and that seems to be more or less the case. But of course that depends on the age and health of the populace.
Italy even before their medical system got overwhelmed is both a lot older and less healthy than most Asian populations and they were trending more like 15% fatal because it was mostly much older people getting sick. It is a lot worse now because they cannot provide the medical care most of the elderly need (theirs is also roughly 38% case fatality rate now, though again, they are likely missing some cases that are more mild. However, they are doing a better job testing than the US is still, so they are likely missing fewer cases).
In the 80+ group more than half of people will need hospital level care or they will die.
It won't be the end of days, but if we do nothing, likely most people on Earth will get infected in the next couple of years (estimated at 60-70% in the next 12 months). Of those, most of the very elderly will die because no health care system can keep up with that. A lot of the younger people too. The hospitalization rate in the 30-50 age range is still pretty high. About 10%. it is just that they will respond well to treatment where someone a lot older will not. Which is why in the 30-39 age range the case fatality rate is below 1%. But if you cannot provide medical care to them, it is going to sky rocket to more like 5-10%.
That is what we are working to avoid is overwhelming our medical system so most of the people who are going to get sick, do survive. If we don't do anything, millions will die who could be saved. Same thing happened with the Spanish Flu. Cities that did nothing got overwhelmed and tens of thousands died. Cities that worked hard to prevent the spread mostly DID have as many people get sick. It just was a slow spread that the medical establishment could cope with and could treat patient. So hundreds and thousands died instead of tens of thousands.
Something that is throwing off a lot of people is that you can spread it when asymptomatic, both before developing symptoms and after recovery. The studies that have looked at them show that people are typically infectious 1-2 days after being infected, which means they are likely 3-4 days before becoming symptomatic. They can also spread it for 1-8 days AFTER recovering (IE no more symptoms). Very, very few people remain asymptomatic. The vast majority eventually become symptomatic, even if it is only mild symptoms.
Deaths lag a lot more than infections. Its 5 days on average to become symptomatic (95% range is 4.5-5.8d). Average recovery period for mild cases is 8d on average after becoming symptomatic with a typical range of 6-14 days for mild cases. Moderate cases are typical 14-23 days. Severe and critical cases are typically 14-28 days with a few cases being as long as 8 weeks.
Deaths, even in unhealthy elderly people from the time they become symptomatic to death is 2-8 weeks. There are very, very few cases reported where someone became symptomatic and then died a day or two later. Most people start with mild symptoms and progress after a week suddenly. Average amount of time from symptomatic to hospitalization is 8 days. Average progression from mild to severe symptoms is less than 12 hours.
So if you have 10,000 cases on day 1 and 160,000 on day 12, which represents a doubling every 3 days and roughly is the trend the US has been on, the deaths you are seeing on day 12 are mostly the people who became symptomatic on day 1. Not the 150,000 cases that developed between day 1 and day 12. All those people who got sick on day 2-12 are mostly going to start dying in the following days and the nature of exponential curves, 70% of those who will die won't be dying for at least another 2 weeks. And in 2 weeks, most of the people who would then be dying got infected on days 13-24. So on and so forth. Eventually the disease is self limiting once enough people get sick, but it doesn't start slowing down on its own until about 1/4th of the US population has gotten sick.
Also a fun fact, no known human coronavirus produces long lasting immunity. Generally immunity lasts 1-2 years. So if you do get sick now, odds are pretty high you can get reinfected in a year or two (if not sooner as some people display shorter lasting immunity). So shy of an effective anti-viral or a vaccine (and a vaccine that would likely have to be re-administered perhaps annually) we will likely have somewhere between 2-5% of the population dying from this every single year, depending on how effective we can make our health care system at treating people and if any prior exposure at least aids somewhat in fighting off future infections, even if you aren't immune (jury is out on that, but it doesn't look good).
