1979 – The eradication of the smallpox virus is certified, making smallpox the first of only two diseases that have been driven to extinction (with rinderpest in 2011 being the other). Smallpox was an infectious disease caused by variola virus (often called smallpox virus), which belongs to the genus Orthopoxvirus. The earliest evidence of the disease dates to around 1500 BC in Egyptian mummies. The disease historically occurred in outbreaks. It was one of several diseases introduced by the Columbian exchange to the New World, resulting in large swathes of Native Americans dying. 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. Smallpox is estimated to have killed up to 300 million people in the 20th century and around 500 million people in the last 100 years of its existence. Inoculation for smallpox appears to have started in China around the 1500s. Europe adopted this practice from Asia in the first half of the 18th century.[24] In 1796, Edward Jenner introduced the modern smallpox vaccine. 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 initial symptoms of the disease included fever and vomiting. This was followed by formation of ulcers in the mouth and a skin rash. Over a number of days, the skin rash turned into the characteristic fluid-filled blisters with a dent in the center. The bumps then scabbed over and fell off, leaving scars. 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. Prevention was achieved mainly through the smallpox vaccine.