National Library of Medicine
A highly contagious viral disease now controlled by inoculations. Some experts say that over the centuries, it has killed more people than all other infectious diseases combined.
Symptoms of smallpox are flu-like, followed by a rash with flat red sores. In 1977, the last case of smallpox was identified. Over the next two years no more cases were found and in 1980, the World Health Organization declared that "smallpox is dead".