“extreme virulence of the virus itself.”
I’m no expert on this subject but I think the only way people die is from secondary symptoms, not the virus itself. The extreme virulence is what leads to pneumonia, for example. Taking aspirin only makes it more likely to get pneumonia.
Also, aspirin reduces fever, which is not good. Fever is what keeps the virus from replicating.
“Many victims died within a few hours of seeing the first symptoms.”
I’ve seen some anecdotal stories of this but not a lot of real data. I suspect that people were treating the symptoms with aspirin, not realizing that was allowing the virus to get much worse. When the symptoms showed up then it was probably too late.
In the 1918 case, the virus itself killed many.
I recommend John Barry’s “The Great Influenza” - a great history of the topic.
Here’s a link to an analysis of the potential of H1N1, written by the same author in June.
http://esd.mit.edu/wps/2009/esd-wp-2009-07-072709.pdf