The historical narrative of the Spanish conquest of Mexico states that, armed with modern weapons and Old World diseases, several hundred Spanish soldiers toppled the Aztec empire in 1521.
By the end of the century, the invaders had wiped out 90 percent of the natives, according to Jewish authors like Jerod Diamond of “Guns, Germs and Steel.” Diamond argues that Eurasian civilization is not so much a product of ingenuity but of opportunity and necessity. That is, civilization is not created out of superior intelligence but rather is the result of a chain of developments, each made possible by certain preconditions, including advantages in germ resistance.
It’s a key piece of the “Black Legend,” the tales of atrocities committed by the Spanish Inquisition and colonizers of The New World. But it may be just that — legend, according to Rodolfo Acuña-Soto, a Harvard-trained epidemiologist.
Acuña-Soto, who spent 12 years dissecting colonial archives, census data, graveyard records and autopsy reports. He’s convinced that many historians are wrong about what killed the Aztecs.
“The problem with history is that it’s very ideological,” Acuña-Soto said. “In this case, it was a beautiful way of accusing the Spaniards of unimaginable cruelties and of decimating the population of Mexico.”
More recent work by scientists swept aside smallpox, measles, mumps and influenza (brought in by Europeans) as likely suspects. They instead point to a typhoid-like “enteric fever” for which there is DNA evidence on the teeth of long-dead victims.
A physician named Francisco Hernandez, who witnessed the outbreak in 1576, stated that the symptoms suffered included high fever, severe headache, vertigo, black tongue, dark urine, dysentery, severe abdominal and chest pain, head and neck nodules, neurological disorders, jaundice and profuse bleeding from the nose, eyes and mouth. Death frequently occurred within three to four days. This epidemic mainly afflicted young people and seldom elder ones.
A study by Ashild Vagene of the University of Tuebingen in Germany states, “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 estimated at 12-15 million. The first cocoliztli of 1520-1521 devastated 8 million.”
Study co-author Alexander Herbig, also from Tuebingen University, stated, “We tested for all bacterial pathogens and DNA viruses for which genomic data is available,” and salmonella enterica was the only germ detected.
The epidemic in 1576 occurred after a drought stretching from Venezuela to Canada, according to a study published in the science journal “Nature Ecology & Evolution.” The cocolitzli epidemics appeared to be preceded by several years of drought. Acuña-Soto also found that the epidemics didn’t happen during the drought. They appeared only in the wet periods that followed it. That was the crucial clue he had missed: It was raining when people got sick.
Analyzing DNA extracted from 29 skeletons buried in a cocoliztli cemetery, scientists found traces of salmonella enterica bacterium of the Paratyphi C variety. This is virulent haemorrhagic fever, or “bleeding-eye fever,” that is transmitted through tick-bites and contact with the blood of infected animals. Very ill patients may suffer organ failure after the fifth day of illness.
All types of hemorrhagic viruses share traits. They are extremely simple, composed only of RNA enveloped in a fatty membrane, and they all must develop first in an animal host, often rodents or bats. They are commonly spread by insects, such as ticks or mosquitoes. An insect bite or direct exposure to rodent feces or urine or indirect exposure through windblown particles can pass the virus to humans. The virus must have been native-born.
The threat of such lethal disease still exists given the prolific rat populations in California cities.