In the beginning of the 20th century, the Spanish Flu pandemics led to a wide discussion among the international scientific community about the nature and the causal agent of the disease. This paper intends to discuss some of the controversies that characterized the medical discourse about this manifestation of the flu, looking at the pre-bacterial theories and the bacterial notion of the disease, in particular Pfeiffer's proposition, and the supposition of the action of invisible agents, so called filterable viruses.
History of the pandemics; Spanish influenza; Medical theories