5. Smallpox
As we already mentioned, in 1980, the World Health Assembly declared the world free of smallpox. But before that, humans battled smallpox for thousands of years, and the disease killed about 1 in 3 of those it infected, leaving survivors with deep, permanent scars and, often, blindness.
Mortality rates were far higher in populations outside of Europe, where people had little contact with the virus before visitors brought it to their regions. For example, experts estimate 90 percent of the native population of the Americas died from smallpox introduced by European explorers.
Only in the 20th century, smallpox killed 300 million people. “It was something that had a huge burden on the planet, not just death but also blindness, and that’s what spurred the campaign to eradicate from the Earth,” Adalja said.
