In 1901, Dr. Allan Warner of the Isolation Hospital at Leicester, England, took a series of photographs of patients with smallpox.

This one is possibly the most famous.

The two boys are said to be 13 year-olds and infected with smallpox simultaneously during an epidemic of the disease in the United Kingdom, one of the last big ones there.

The boy on the left shows a full-blown presentation of smallpox, with the pus-filled pustules all over his body, concentrated on his face and arms. The boy on the right is at the hospital in the same isolation unit, because he is also showing some pustules (and perhaps a slight fever or malaise), though certainly not as many.

The difference is in the fact the boy on the right was vaccinated and didn't develop serious symptoms.

The earliest written description of a disease like smallpox appeared in China in the 4th century CE (Common Era). Early written descriptions also appeared in India in the 7th century and in Asia Minor in the 10th century.

Ali Maow Maalin was the last person to have naturally acquired smallpox caused by variola minor in October 1977.

Almost two centuries after Edward Jenner hoped that vaccination could annihilate smallpox, the 33rd World Health Assembly declared the world free of this disease on May 8, 1980.