Which of the following diseases has been eradicated worldwide?

Smallpox

The correct answer is Option (4) - Smallpox

Smallpox, caused by the variola virus, was a highly contagious and devastating disease that plagued humanity for thousands of years, causing millions of deaths before its eradication. It is estimated to have existed for at least 3000 years.

Edward Jenner developed the smallpox vaccine in 1796, marking the first successful vaccine in history. Observing that milkmaids previously infected with cowpox did not contract smallpox, Jenner demonstrated that inoculation with a similar virus could prevent smallpox.

In 1967, the World Health Organization (WHO) launched an ambitious plan to eradicate smallpox. This effort involved widespread immunization campaigns and surveillance worldwide. The last known natural case of smallpox occurred in Somalia in 1977. In 1980, WHO officially declared smallpox eradicated, making it the first and only infectious disease to achieve this feat. This achievement stands as one of the most significant and impactful successes in the history of public health.