The disease that has been eradicated from the world is smallpox. Smallpox, caused by the variola virus, was a highly contagious and deadly disease. It manifested with a fever, rash, and painful sores all over the body. However, due to a global vaccination campaign, smallpox was successfully eradicated in 1980. This means that the disease no longer exists naturally in any part of the world, making it the first disease to be eradicated by human effort. Leprosy, poliomyelitis, and chickenpox are all diseases that still exist today. Leprosy is a chronic infection caused by the bacteria Mycobacterium leprae, poliomyelitis is a viral infection that can cause paralysis, and chickenpox is a highly contagious viral infection characterized by itchy blisters.