Smallpox was wiped out nearly four decades ago but talk has resurfaced out of fear it could be used in a future terror attack.

U.S. regulators approved treatment for smallpox on Friday, citing fear that it could be used as a biological weapon. Smallpox is a fatal infectious disease that killed nearly 300 million people across the globe in the 20th century. Variola virus, the virus that prompts the onset of smallpox, was typically spread by human-to-human contact.

Symptoms of smallpox included pus-filled sores, fever and fatigue 10 to 14 days after infection. Complications that arose from smallpox were encephalitis, corneal ulcerations and blindness.

A vaccination campaign in the 1980s allowed for the eradication of smallpox.  Those born since then have not been vaccinated for a disease that no longer exists, which poses a humanitarian threat when considering biological warfare.

Dr. Scott Gottlieb, FDA commissioner, said in a statement, “To address the risk of bioterrorism, Congress has taken steps to enable the development and approval of countermeasures to thwart pathogens that could be employed as weapons.

SIGA Technologies of New York delivered 2 million treatments of the vaccination, TPOXX, to the government.SIGA Technologies develops biological, chemical, nuclear and radiological vaccinations and medications.

“This new treatment affords us an additional option should smallpox ever be used as a bioweapon,” Gottlieb said.

Monkeys and rabbits were infected with a similar virus to test the effectiveness of TPOXX. The makers of TPOXX indicated more than 90 percent survived. Several hundred volunteers were also tested.

The vaccination can be used to prevent the infection but must be done within five days of exposure, before the symptoms appear. At that time, treatment will consist of taking the TPOXX capsule twice daily for two weeks.

A statement on the CDC website says, “There is credible concern that in the past some countries made the virus into weapons, which may have fallen into the hands of terrorists or other people with criminal intentions.”

Only the U.S. Centers for Disease Control and Prevention (CDC) and the Russian State Centre for Research on Virology and Biotechnology are the only two labs in the world approved to have isolated versions of smallpox.