Normally, the Classic period in Mesoamerica is characterized as the stage in which the arts, science, urbanism, architecture, and social organization reached their peak. This period was also dominated by the influence of Teotihuacan throughout the region, and the competition between the different Mesoamerican states led to continuous warfare.
The most common name for the killer virus, the Spanish flu, implied, of course, that it originated in Spain. Perhaps this was because there were serious outbreaks in both Madrid and Seville that infected eight million people in May of 1918 alone, even almost taking out the king himself, Alfonso XIII.
In a 2006 study in the journal Nature, researchers using molecular genetics techniques demonstrated that the Spanish influenza triggered exceptionally high and sustained expression of pro-inflammatory cytokines and chemokines by the immune system, accounting for the relative severity of Spanish influenza symptoms compared to other flu viruses.