The Centers for Disease Control classifies the virus as a major threat because it's easily transmitted, like a cold. The disease presents with lesions on the skin, and for patients that survive, blindness and disfigurement is common.
Smallpox is best treated with a combination of a preventive vaccine, which can work even days after infection, and an antiviral like Arestvyr.
Some experts argue this makes the U.S. purchase of Arestvyr unnecessary because the country already has millions of smallpox vaccines in reserve.
"Is it appropriate to stockpile it? Absolutely," Dr. Richard H. Ebright of Rutgers University said. "Is it appropriate to stockpile 2 million doses? Absolutely not. Twenty thousand seems like the right number."
Read more at the Times.