The undoubted occurrence of non-pneumonic or apneumonic influenza naturally suggests the idea that in the pneumonic form we may have been dealing with a process in which bacteria other than those causing the influenza were at work. - Dr. David Riesman, "Influenza - Remarks upon Symptoms, Prevention, and Treatment" In The Medical Clinics of North America, Vol. 64, Issue 6, pp. 903, 904.
The articles in this cited volume were published in Philadelphia in 1918, during the avian (bird) flu epidemic that killed thousands worldwide.