By: James Peacock

Your high school history teacher probably taught you all about the Aztecs of Mexico. The once mighty empire was renowned and feared during their time. They conquered many different peoples to construct their vast realm. They seemed unstoppable. However, even the mighty can fall, when disease has a say in the matter.

History Lesson

In March of 1519, Hernan Cortes landed on the east coast of Mexico with an army of Spanish soldiers. These men, having heard stories of a great civilization, set out to find the Aztec Empire. The Aztecs had been the preeminent power in central Mexico for a couple of centuries, and had built quite a successful kingdom. However, this empire was largely built on conquering other tribes, and these tribes held animosity towards the Aztecs. The Aztecs built their capital city on Lake Texcoco – as a prophecy had foretold that an eagle with a snake in its talons perched on a cactus would show the tribe where to settle. This symbol would eventually find its home on the Mexican flag, and the city, Tenochtitlan, would eventually become Mexico City. The Spaniards that sought the capital city were motivated by a few factors, but most importantly was the search for gold and profitable trade routes. By making contact with the Aztecs, the Spanish would then have access to the large amounts of Aztec gold, as well as the resources of central Mexico. The Aztecs viewed the Spanish conquistadors as gods, as yet another prophecy predicted their arrival. This prophecy, though, foretold the end of the world. In a sense, that was exactly what the Spanish arrival signaled.

Through the use of Indian allies, Cortes was able to find the city of Tenochtitlan, and he and his conquistadors were welcomed into the city as gods. The ruler of the Aztec Empire at the time, Montezuma II, was cautious not to anger the Spanish. Tensions between the Spaniards and the Aztec rose exponentially after their arrival, and eventually these tensions would boil over. There were a series of battles between the Aztecs and the allied forces of Cortes and other Native American tribes. The Spanish and their allies, helped by superior technology, horses, and fighting techniques, would eventually prevail over the Aztecs in 1521. Montezuma II was held prisoner, but was eventually killed by rocks during a riot. With little leadership, the Aztecs and most of their land would fall under the control of Spain, who named the new colony New Spain. The conquest and further subjugation of the Aztecs would prove to be quite costly. Prior to the Spanish arrival, there were as many as 25 million Native Americans in the area now known as Mexico. Less than 50 years later the population of Native Americans would be around 5 million people. There were many causes for this rapid depopulation, including brutal slavery, continued warfare, and diseases brought to the New World via the Columbian Exchange.

The Colombian Exchange refers to the exchange of ideas, goods, and diseases between Europe and the Americas. The Columbian Exchange was, though, a two way street, as both Europe and the Americas gained things from the Exchange. Items such as corn, tomatoes, tobacco, and horses were introduced to societies across the world. Technology, religion, and ideas were also exchanged. Unbeknownst to them, Europeans also carried over a number of diseases to the New World. In many cases, these were diseases that Europeans had developed a natural resistance to. The most famous of these diseases include smallpox, the plague, and now, Salmonella.

Diseases the Cause of the Downfall

The introduction of these diseases was devastating to native populations. Epidemics were common after the arrival of the Europeans, some accidental and some started purposefully. Two epidemics alone, one in 1545 and one in 1576, accounted for between 7 million and 18 million deaths. The 1545 outbreak was studied recently by researchers who took samples from burial grounds in Mexico. This outbreak is thought to have lasted for 5 years, eventually coming to a close in 1550. Measles, smallpox, and other diseases are all thought to have been potential causes of this outbreak, but this new study points in a new direction. Samples taken from the teeth of buried remains in Oaxaca, located in southern Mexico, had several test positive for Salmonella contamination. The samples were compared to databases of genetic sequences in order to confirm the presence of Salmonella. A couple of samples were further sequenced, and these DNA sequences were related to a strain we now know as Paratyphi C. This bacteria is still around today, where it causes a high fever and other typhus-related symptoms. The strain is fatal in 10 to 15 percent of cases if left untreated. A similar strain of Salmonella was previously found in remains from Norway, which indicates that the disease was present around Europe prior to the colonial era, making it possible for the disease to be brought to the New World.

These findings suggest that Salmonella had a hand in the many outbreaks and epidemics that rocked Aztec society after the arrival of the Spanish. However, it is still unknown just to what degree Salmonella caused these outbreaks. There were many different diseases causing infection at that time, and likely these illness would spiral out of control. For instance, Salmonella is transmitted by fecal matter, and in a society already decimated by disease and warfare, hygiene would have been largely nonexistent. Further study is required to pinpoint the extent and time frame in which Salmonella and other diseases made their mark on American history.

Today, Salmonella bacteria are one of the most common causes of foodborne illness. Health officials first began to actively track Salmonella infections and outbreaks in 1962. Dr. Salmon first classified the bacteria and its effects more than 125 years ago. There are many different strains of Salmonella bacteria, but all will cause illness in humans. The 32 different serotypes, or strains, of Salmonella bacteria help investigators pinpoint potential outbreaks, as well as their sources. Health officials have studied the incidence rates of infections based on the pathogen responsible. In many cases, scientists have established an average rate of infections, because people are always being sickened by foodborne illnesses. However, when the number of infections reported increases rapidly and suddenly, it is an indicator to health officials that an outbreak is taking place. Scientists employ a number of ways to track and detect a foodborne illness outbreak. Through studies like this one, researchers and health officials can gain a better understanding of modern illness outbreaks.