I have seen quite a few healthy people in my circle of friends that were hospitalized. Some even in their early 20's, perfect health. No one died but a couple almost did. And then I've seen elderly folks catch it that smoked all their lives and only have a headache for two days. It is highly dependent on the individual, apparently. But for those susceptible, such as myself, it was serious. My O2 sat went down to 90% and stayed there for two and a half weeks. A few times I was ready to get myself admitted, but I waited it out.