In 1545, twenty-four years after the Spanish conquest of the Aztec empire,
an epidemic of a malignant form of a hemorrhagic fever appeared in the high
lands of Mexico. The illness was characterized by high fever, headache, and
bleeding from the nose, ears, and mouth, accompanied by jaundice, severe a
bdominal and thoracic pain as well as acute neurological manifestations. Th
e disease was highly lethal and lasted three to four days. It attacked prim
arily the native population, leaving the Spaniards almost unaffected. The h
emorrhagic fevers remained in the area for three centuries and the etiologi
c agent is still unknown. In this report we describe, and now that more inf
ormation is available, analyze four epidemics that occurred in Mexico durin
g the colonial period with a focus on the epidemic of 1576 which killed 45%
of the entire population of Mexico. It is important to retrieve such disea
ses and the epidemics they caused from their purely historical context and
consider the reality that if they were to reemerge, they are potentially da
ngerous.