Does the COVID-19 have any known special features beyond other known pathogens which could allow it to cause a death toll of millions? Or if not, where does it fit in if there is a way to do such estimation?
What I can think of, or in combination, but I do not have comparison data to other pathogens:
- can survive on surfaces and in a larger range of conditions than others?
- higher contagiousness?
- humans do not immunize?
For example the 2009 flu pandemic caused way more people to become ill and half a million to die but had relatively low mortality rate below 0.1%. So is COVID-19 more dangerous if it has mortality rate about 2%?
Does it have potential to become the new Spanish flu - what is scientific argumentation here? (or what yet needs to be found out). Here I wonder also, how much Spanish flu numbers can be told to be somewhat "inflationary" by medical conditions of that time - if not balanced by today's population's density and mobility.