Looks like the first effort to eradicate smallpox was in 1950, and then by 1975 it existed only in Africa. Victory was declared in 1980. https://en.wikipedia.

Looks like the first effort to eradicate smallpox was in 1950, and then by 1975 it existed only in Africa. Victory was declared in 1980. https://en.wikipedia.org/wiki/Smallpox#Eradication https://en.wikipedia.org/wiki/Smallpox#Eradication Obviously every disease is different, but since it's only been done twice EVER, I would learn toward the burden of proof being on those to explain why it's realistic, not for those to explain why it's UNrealistic. I would summarize it as "The world is very big and there are a lot of people and places that got infected" ...