The ‘current’ understanding of the Spanish influenza is that at least three separate jumps into virulence were caused by continuing mutation of some aspect of the strain involved. I don’t know if ‘permissible’ research on the particular clone(s) of that virus that have been recovered will show the peculiar lethality or expose its particular causes after sequencing and folding analysis.
There is an interesting characteristic to FIP infections in cats. Virtually all cats are exposed to feline coronavirus from an early age, and some of them exhibit transient symptoms of infection which form immunity and are overcome early in life. In about a third of a percent of cats, though, a clone of the virus develops which produces chronic infection of a couple of types, classically ‘always’ resulting in death over a course of weeks to months. The interesting thing is this: once the infection proceeds to the ‘peritonitis’ stage, the cat is essentially no longer an infectious danger to other cats in the same household, even though the unmutated virus is highly transmissible. Few people seem to have remarked on this as late as early fall (when I stopped following the research literature temporarily), but it appears we might be looking at a similar mechanism with the most recent stats that charlie hebdo has provided. This of course would be highly preferable to any virus that has both high transmissibility (as the Chinese coronavirus has demonstrated so far) and also induces an exaggerated but essentially futile immune response (as is the cause of death in FIP).
Back in the fall of 1957, there was great concern of what was feared to be a flu epidemic. Not much vaccine was initially available, and my college decided to make certain that faculty and instructors were protected. I was given a shot on Thursday; I did not feel really well on Friday; I went to bed after lunch Saturday (and disgusted the student who had to see to me)–and was able to be back out Sunday afternoon.
From what I understand, a significant number of deaths from viral infections (flu, SARS, 2019 Corona) are due to secondary infections such as bacterial pneumonia. It’s quite possible that China has improved response to treating secondary infections as compared to the SARS epidemic.
As an aside, Oswald Avery of the NYC public health department spent a couple of decades researching the acteria associated with pneumonia. There were two prominent strains, one relatively benign and the other virulent. What was more puzzling was that interactions between the benign and virulent strains could lead to the benign strains becoming virulent and after over two decades of research he determined that the genetic transfer was done by transfer of DNA, which at the time was not considered to have anything to do with genetics.
A problem about this virus will probably rear its head here in the US in about 6 weeks. that is when the supply chain of goods from China may dry up . The ships with goods will not be coming. So the RRs especially UP and BNSF will see a drop in intermodal continers coming over. Now how much will be taken up by other countries and other areas of China will leave to those who understand the supply chain much better ?