The majority of deaths during the influenza pandemic of 1918-1919 were not caused by the influenza virus acting alone, report researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. Instead, most victims succumbed to bacterial pneumonia following influenza virus infection.

Dude. The Spanish Flu is a virus, right from the source you linked. The people just died because of the bacterial pneumonia after the virus damaged the immune system.