Thirty years ago today, doctors in Somalia diagnosed the last case of naturally occurring smallpox in the world–a final case in a one of the worst wars with nature that humans had ever seen. Two years later, the World Health Organization declared the disease officially eradicated.

One of the most feared diseases in history, smallpox has a mortality rate between 30-35%. Those that survived the horrible illness often had disfiguring scars, and were sometimes left with residual effects such as blindness and infertility. In just the 20th century alone, smallpox claimed 300-500 million lives.

Although a vaccine for smallpox was created as early as 1798, until the 1950s smallpox continued to infect an estimated 50 million people a year. That figure dropped by 1967 to between 10 and 15 million as vaccination became more prevalent. In that year, WHO began the Global Intensified Eradication Program, which included mass vaccination, and containment of infection by vaccinating close contacts of those infected.

To this day, smallpox remains the only human infectious disease to have been completely eradicated.