Story highlights TPOXX was given priority review as a potential bioterror preparedness measure

Smallpox was eradicated in 1980 thanks to vaccination efforts

(CNN) The US Food and Drug Administration announced Friday its approval of the first drug to treat smallpox.

The contagious disease was eradicated in 1980 thanks to vaccination efforts, but there are concerns that it could be used in a bioterror attack.

Smallpox is spread by direct contact, and symptoms begin 10 to 14 days after a person is infected, according to the FDA. They include fever, headache, backache and exhaustion.

The hallmark is a rash beginning as small, pink bumps that develop into pus-filled sores, which become scabs and then scars. Some people experience inflammation of the brain (called encephalitis), sores on the surface of the eye (called corneal ulceration) and blindness, all considered complications of the virus.

The US Centers for Disease Control and Prevention and the Russian State Centre for Research on Virology and Biotechnology are the only two labs in the world approved and known to have smallpox.

Read More