Did you know that smallpox is estimated to have killed between 300-500 million people in 20th century?

even though the last person to die from orthopoxvirus variola major was in 1978 i still doubt they can claim its been exterminated. We have yet to find the reservoirr for many bacteria and viruses such as hemorrhagic fevers and vibrio cholera, so how can we know smallpox has been eliminated.