Ancient Killers are Unmasked

Today's news brought new insight into two of history's massively deadly epidemics: (1) what killed the ancient Aztecs in Mexico after the Spanish arrived?; and (2) how did the Black Death spread so quickly in Europe? The Guardian has the story about the Aztecs:

Within five years as many as 15 million people – an estimated 80% of the population – were wiped out in an epidemic the locals named “cocoliztli”. The word means pestilence in the Aztec Nahuatl language. Its cause, however, has been questioned for nearly 500 years.

On Monday scientists swept aside smallpox, measles, mumps, and influenza as likely suspects, identifying a typhoid-like “enteric fever” for which they found DNA evidence on the teeth of long-dead victims.

“The 1545-50 cocoliztli was one of many epidemics to affect Mexico after the arrival of Europeans, but was specifically the second of three epidemics that were most devastating and led to the largest number of human losses,” said Åshild Vågene of the University of Tuebingen in Germany. Vagene co-authored a study published in the science journal Nature Ecology and Evolution.

In terms of numbers of deaths, the Aztec losses were nearly as large as those caused by the plague in Europe. BBC News tells us how that spread so fast:

The rodents and their fleas were thought to have spread a series of outbreaks in 14th-19th Century Europe.

But a team from the universities of Oslo and Ferrara now says the first, the Black Death, can be "largely ascribed to human fleas and body lice".

As I noted in a post a few years ago, the rapid spread of the disease through European villages did not seem consistent with bites from fleas carried by rats. And the models utilized by these researchers were consistent with human-to-human spread of fleas and lice.

The study, in the Proceedings of the National Academy of Science, uses records of its pattern and scale. 

The Black Death claimed an estimated 25 million lives, more than a third of Europe's population, between 1347 and 1351.

These two stories illustrate the incredible scientific advances being made to uncover the past. And they remind us of the incredible importance of continuing governmental and societal support of this kind of research.