What is the source of the 0.4% anything I am seeing globally is above 10%
It comes from the Stanford antibody study, which is really the first U.S. attempt to estimate a more accurate denominator rather than relying on "confirmed cases" in a situation where you almost have to be hospitalized to get tested in many places. But it is very preliminary.
The next-best estimate would have to be South Korea's data because they started out testing a wide swath of the population (though they later narrowed it based on contact tracing, so the tested group is still somewhat biased toward confirmed exposures). Their fatality rate is 2%. The higher global rate is largely because most countries are only testing those with symptoms, either because their testing capacity is limited or because they haven't created the infrastructure for population-wide testing in a time when people are being discouraged from leaving their homes.
Based on what I've been hearing from doctors and nurses in New York, Detroit and other hot spots, if anything people aren't frightened enough by this. They're pleading for people to take this virus seriously because they've seen so many people of all ages and health descriptions die from it and there wasn't anything they could do.
Asking medical personnel is always biased toward action, though, because even one horrible case is enough to make an impression on a human level. They inherently encounter the worst possible outcomes of everything and that can skew their perception of the situation as a whole. I know quite a few nurses who think trampolines and backyard pools should be illegal because they've seen injuries and deaths from them that they don't think the potential fun of safe use justifies the risks, and don't even get them started on what they think of gun ownership.
If the Coronavirus pandemic is similar to the Spanish Flu, we're in for a couple of bad years unless we can solve this thing quick with either a reliable treatment or a vaccine. It's ironic to me that 100 years after the last pandemic we still aren't on top of this kind of thing. All of our advances in science and technology and we're still stuck in our houses hiding from a virus, just like 100 years ago.
There's actually a fair bit of evidence that this won't be the same, though. One of the reasons the Spanish flu was as bad as it was for as long as it was is because it was able to get a foothold in previously-unexposed populations with each successive wave because our world was a much less mobile place at the time. The first wave in the U.S. was concentrated around a handful of military bases. The second wave, when our soldiers were starting to come home from war, hit the major cities... and because those cities had few-to-no cases during the first wave, everyone was just as vulnerable to it as they would have been if it had been a never-before-seen virus. It was the third wave that was a genuine rebound like they're worried about with COVID19.
The awful thing about a modern pandemic is how quickly it spreads around the world in an era of global travel, and how quickly it spreads within each country via planes, trains and interstates. But that is also the thing that should make successive waves of this virus less severe than the initial outbreak. Because it is going to have a much harder time finding pockets where no one has been exposed, and even low levels of immunity in the population exert some downward pressure on spread by interrupting the chain of transmission in places. Not enough for containment or control, of course - we know even relatively modest numbers of anti-vaxxers can disrupt herd immunity to measles, particularly because they're often clustered - but enough that second and subsequent introductions are less overwhelming than the first wave.
