Smallpox
Smallpox was an infectious disease caused by variola virus (often called smallpox virus) which belongs to the genus Orthopoxvirus.[7][11] 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,[10] making smallpox the only human disease to be eradicated.[12]
The initial symptoms of the disease included fever and vomiting.[5] This was followed by formation of ulcers in the mouth and a skin rash.[5] Over a number of days, the skin rash turned into the characteristic fluid-filled blisters with a dent in the center.[5] The bumps then scabbed over and fell off, leaving scars.[5]
The disease was transmitted from one person to another primarily through prolonged face-to-face contact with an infected person or (rarely) via contaminated objects.[6][13][14] Prevention was achieved mainly through the smallpox vaccine.[9] Once the disease had developed, certain antiviral medications could potentially have helped, but such medications did not become available until after the disease was eradicated.[9] The risk of death was about 30%, with higher rates among babies.[6][15] Often, those who survived had extensive scarring of their skin, and some were left blind.[6]
The earliest evidence of the disease dates to around 1500 BC in Egyptian mummies.[16][17] The disease historically occurred in outbreaks.[10] In 18th-century Europe, it is estimated that 400,000 people died from the disease per year, and that one-third of all cases of blindness were due to smallpox.[10][18]
Smallpox is estimated to have killed up to 300 million people in the 20th century[19][20] and around 500 million people in the last 100 years of its existence.[21] Earlier deaths included six European monarchs.[10][18] As recently as 1967, 15 million cases occurred a year.[10]
Inoculation for smallpox appears to have started in China around the 1500s.[22][23] Europe adopted this practice from Asia in the first half of the 18th century.[24] In 1796, Edward Jenner introduced the modern smallpox vaccine.[25][26]
In 1967, the WHO intensified efforts to eliminate the disease.[10] Smallpox is one of two infectious diseases to have been eradicated, the other being rinderpest (a disease of even-toed ungulates) in 2011.[27][28]
The term "smallpox" was first used in England in the 16th century to distinguish the disease from syphilis, which was then known as the "great pox".[29][30] Other historical names for the disease include pox, speckled monster, and red plague.[3][4][30]