A new, possible explanation of the destruction of the Aztec Empire–don’t know if it will stand up. In Discover:
There seemed little reason to debate the nature of the plague: Even the Spanish admitted that European smallpox was the disease that devastated the conquered Aztec empire. Case closed.
Then, four centuries later, Acuña-Soto improbably decided to reopen the investigation. Some key pieces of information—details that had been sitting, ignored, in the archives—just didn’t add up. His studies of ancient documents revealed that the Aztecs were familiar with smallpox, perhaps even before Cortés arrived. They called it zahuatl. Spanish colonists wrote at the time that outbreaks of zahuatl occurred in 1520 and 1531 and, typical of smallpox, lasted about a year. As many as 8 million people died from those outbreaks. But the epidemic that appeared in 1545, followed by another in 1576, seemed to be another disease altogether. The Aztecs called those outbreaks by a separate name, cocolitzli. “For them, cocolitzli was something completely different and far more virulent,” Acuña-Soto says. “Cocolitzli brought incomparable devastation that passed readily from one region to the next and killed quickly.”
After 12 years of research, Acuña-Soto has come to agree with the Aztecs: The cocolitzli plagues of the mid-16th century probably had nothing to do with smallpox. In fact, they probably had little to do with the Spanish invasion. But they probably did have an origin that is worth knowing about in 2006.