Ali Maow Maalin, the last natural case of smallpox, develops a rash in Somalia. The WHO and the CDC consider this date to be the anniversary of the eradication of smallpox, the most spectacular success of vaccination.

Ali Maow Maalin was a Somali hospital cook and health worker from Merca who is the last person known to have been infected with naturally occurring Variola minor smallpox. He was diagnosed with the disease in October 1977 and made a full recovery. Although he had many contacts, none of them developed the disease, and an aggressive containment campaign was successful in preventing an outbreak. Smallpox was declared to have been eradicated globally by the World Health Organization (WHO) two years later. Maalin was subsequently involved in the successful poliomyelitis eradication campaign in Somalia, and he died of malaria while carrying out polio vaccinations after the re-emergence of the poliovirus in 2013.

Smallpox was an infectious disease caused by Variola virus, which belongs to the genus Orthopoxvirus. The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980, making smallpox the only human disease to have been eradicated to date.

The World Health Organization (WHO) is a specialized agency of the United Nations which coordinates responses to international public health issues and emergencies. It is headquartered in Geneva, Switzerland, and has 6 regional offices and 150 field offices worldwide. Only sovereign states are eligible to join, and it is the largest intergovernmental health organization at the international level.

The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency under the Department of Health and Human Services (HHS), and is headquartered in Atlanta, Georgia.