Probably not that many… It takes a lot for a virus to become completely extinct. Usually a country will have got rid of a certain virus but it still exists somewhere in the world!
Only one can be said to be officially eradicated in the human population: vaccinia virus also known as the dreaded cause of small pox. The world health organisation took on a massive vaccination effort to eradicate the disease from the human population and it is the only disease they have been successful in doing so, with polio almost there. Smallpox only exist in highly controlled and classified government laboratories. Researchers who study small pox work with a variant of the original that is much less virulent (I should know, I used to study small pox!)
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