Cocolitzli – the Great Plague – Mexico 1576 A.D.

In about 1575-6, Mexico was struck by the worst epidemic, the region had ever known. Witnesses there at the time spoke of half or even two thirds of the population succumbing – a higher mortality rate even than the Black Death. The Spanish physicians did not recognise any of the European diseases with which they were familiar and which had also decimated the Indian population: smallpox, measles, typhoid….and so adopted the Nahuatl term, which basically meant “plague”: coclitzli.

There are a number of fairly horrifying medical descriptions of the disease, but the constants were high fever, terrible thirst, bleeding from all the orifices and jaundice. Alonso López, surgeon at the Hospital Real de Indias, wrote:

…The sick suffered an unnatural thirst. They could never get enough water, because the heat of the poison in their stomachs and hearts was so great and when these fumes rose to the brain, in two days they went mad. Those suffering this disease became very yellow and jaundiced. The urine passed by the sick was very dark and very thick. Those who passed much urine were the ones who lived….

In an attempt to understand the disease, autopsies were performed by doctors of both nationalities and again there are detailed descriptions. Usually forbidden by the Church, they had also been allowed at the time of the Black Death for the same purpose. It was noted that none of the doctors taking part in the autopsies contracted the disease – although obviously they would have had no protective clothing of any kind.

Cocolitzli spread with great speed from the Mexican highlands, as far south as Guatemala, but it was noted that infection levels were uneven and there was debate as to whether this was due to ethnic differences or to the very different levels of wealth and hence living conditions of the Spaniards and the Indians. Francisco Hernández de Toledo, court physician to Philip II remarked:

It attacked the young in particular and the old, even if very ill, often succeeded in shaking it off….This is how it seemed to be at the beginning, although little by little it came to affect all sectors of the population, regardless of age and sex.

First it invaded the regions of the Indian tribes, then the places inhabited by Indians and Ethiopians (blacks); then it reached the people of mixed race, Indian and Spanish; still later the Ethiopian areas and then, last of all, it attacked the Spaniards.

Juan Baptista Pomar, of mixed noble indigenous and Spanish heritage, pointed out that although Spaniards were less apt to die than Indians and highlanders died in far greater numbers than those in the richer lowlands, this was also a social issue: “the wealthy, well-dressed, well-housed and well-provided” were the least likely to succumb. Poverty as much as race was the issue.

There was even some awareness that the terrible dislocation of the original society caused by the Conquest might have had an effect. Juan de la Vega, writing an account of his area, says:

In their original state they ate little, living off the countryside on plants and grasses and small creatures and they went naked and were accustomed to bathe at midnight, but now they no longer do these things and they eat more.

Although malnutrition was much more likely to have been a factor than simply change of diet.

The terrifyingly high mortality rate which left whole villages and even regions deserted had very serious implications not only for indigenous culture, but for the survival of the Spanish, who were dependent on their labour.

The Viceroy, D. Martín Enriquez appreciated the desperateness of the situation from the social point of view and exhorted both medical practitioners and the religious to go and provide what physical and spiritual aid they could, while lay helpers were to “go from house to house, cleaning the discharges of the sick, since in truth mismanagement and slovenliness were the cause of great harm, and providing them with clean clothes and supplying them with food.”

In spite of all their efforts, the doctors neither managed to find a cause of the disease nor any effective remedy. Francisco Hernández, in common with most of the other practitioners, relied on the age-old complex drug Atriaca – Theriac – now reformulated with the aid of Aztec pharmacologists using local herbal medicines. It was ineffective.

Some were convinced that cocoliztli could be attributed to astrological phenomena, while many, of course, believed it was God’s punishment for the sins of the people and the traditional processions and prayers were organized to implore mercy.  No doubt the Indians – secretly – also performed rites to appease their ancient gods, whom they felt had been betrayed.

As is almost always the case in times of epidemic, there was the great problem of burying the dead. One of the Jesuit records tells that: …in the churches and cemeteries, there was not an unoccupied space for a single dead person… they threw them into a great trench, young and old together….and as the churches were not sufficient to bury them all – whole fields needed to be consecrated.”

Medical men, both indigenous and Spanish, studied the disease, searching for causes and looking for cures. Bernardo de Sahagún, in his great work on Mexico in Spanish and Nahuatl, names twelve Aztec doctors. There was much discussion then – and the debate is still on-going – as to what the disease really was.

There were repeated waves of cocoliztli, perhaps even earlier – one codex mentions that “in 1549 many Indians died”. It was noted, both in the Nahuatl chronicles and by the Spaniards, that outbreaks occurred when the great drought that afflicted Central and North America across the mid-16th century was briefly broken by heavy rains. It has been suggested that the disease was an indigenous viral haemorrhagic fever and the rains produced a population explosion in the mouse that acted as vector. Recent research, however, has given rise to an alternative theory; that it was in fact a form of salmonella imported from Europe. The debate clearly has political as well as scientific implications.

And then, strangely, at the beginning of the 19th century, cocoliztli seems to have disappeared.

There is a large scientific literature on cocoliztli from the medical pint of view and a useful bibliography in Spanish and English is given in the Wikipedia article. Particularly informative for the non-specialist are articles by Rodolfo Acuna-Soto and others on-line at

Numerous documents, many in the Archivo General de Indias in Seville and various codices, such as the Florentine Codex of Bernardo de Sahagún or the Telleriano-Remensis Codex contain information about the epidemic. The codices are available on-line, but a number of the documents are currently hard to access.

For much of the material in the post I am indebted to the excellent article by Elsa Malvido and Carlos Viesca La epidemia de cocoliztli de 1576 on-line at

There is also an interesting article on the earlier epidemic by Sandra Elena Guevara Flores on-line at;

N.B. In case I have infringed copyright on any occasion, please notify me and I will immediately delete the post.

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