The Pennsylvania lab worker who stumbled across a stash of frozen vials labeled “smallpox” this week can breathe a sigh of relief. The Centers for Disease Control and Prevention said in a statement Thursday that, following testing, scientists were able to confirm that the vials didn’t contain the variola virus, which causes smallpox. According to the CDC, they actually contained vaccinia—the enveloped virus that was used to create the vaccine that eradicated smallpox in the 1970s. Smallpox is considered to be so dangerous that only two facilities on Earth—one in Russia and the other in Atlanta—are allowed to keep samples of it. A lab worker discovered the mislabeled vials while cleaning out a freezer at a Merck facility in Montgomery County, near Philadelphia.
