Humanity was for centuries under the spell of smallpox, a deadly disease caused by a virus named variola . Smallpox was eradicated in 1977, but for this to happen, vaccine technology had to be invented. And it was a worldwide vaccination campaign that drove smallpox to extinction . Nothing else would have eliminated smallpox. A human-specific Orthopoxvirus, variola was encoded by a DNA genome. To propagate continuously, variola established endemicity in highly populated hum

THE GREAT SICKNESS Centuries ago, a deadly epidemic swept through Mesoamerica. Those who lived through it, called this malady cocoliztli , which means sickness or pestilence in the Nahuatl language. It was a hemorrhagic fever . One which in the spring of 1545, appeared out of nowhere in central Mexico's highlands. Cocoliztli spread with the wind, stopping only because the roads ended. Sonora to the north. Guatemala in the far south. Estimates from population censuses put th