Earlier this month, scientists found decades-old vials of the smallpox virus in the storage room of a lab near D.C.
At the time, it was unclear if any of them were viable samples. On Friday, the Centers for Disease Control and Prevention announced that at least two of the six found are live and infectious.
Smallpox was declared eradicated in 1980. A few samples exist, but they're kept in secure labs and pose no risk to the public. The vials found in the Maryland lab-- which once belonged to the NIH-- are thought to be from the 1950s.
The CDC said that no one has been infected from the forgotten vials.
Once the samples are done being tested, they will be destroyed. The CDC announced on Friday that it would be cracking down on lab safety. Two research centers in Atlanta were temporarily shut down following a slew of accidents.
In June, scores of CDC workers were possibly exposed to anthrax while working on what they believed was an inactive sample of the bacteria. As it turned out, the sample was live. On Friday, the CDC also revealed that there was a similar incident took place that involved bird flu.
CORRECTION: This article previously referred to anthrax as a virus. It is a bacterium.