i believe that you are correct. My understanding is that the main cause of mortality was bacterial pneumonia, but only in conjunction with the debilitating effects of viral influenza on the lungs. These bacteria are already present in your upper airway, and thus need not be communicated to you. Your immune system keeps them in check, unless it gets overwhelmed by the flu, then they colonize your lungs.

Therefore, I suppose a future influenza epidemic could take the same course. The cause of death is respiratory failure from opportunistic pneumonia. But the precipitating event is the influenza virus.

As I mentioned, a main limiting factor in saving patients from this fate is the availability of respiratory support in the form of ventilators. There are (or were) already national stockpiles of antibiotic medicines, which will help a lot, and which were, of course, unavailable in 1918.

Jeff

I should add that, although I've had a lot of briefings and training in dealing specifically with this, and have seen some of the planning and forecast documents, I am certainly not any sort of expert on this subject.