It seems that the SARS virus did the same thing. Most people died of pneumonia caused by the person's own white blood immune cells.
Cortico-steroids, which suppresses the immune system slightly, was the most effective treatment for SARS.
I wonder how an otherwise healthy senior with an over active immune system (allergies) would fare with this virus? I mentioned to an anaesthetist once as I was going into surgery that I had lots of allergies and he looked at my chart and said "you probably will never have cancer". Has anyone else ever heard this?