Vials labeled 'smallpox' were uncovered in a freezer at a Pennsylvania laboratory, the Associated Press reports.
It adds that the vials were uncovered by a worker who was cleaning out the freezer at the unnamed facility where vaccine research is conducted. Smallpox, caused by the variola virus, is a deadly disease that has been deemed eradicated by the World Health Organization, the AP says, adding that two sites, one at the Centers for Disease Control and Prevention in Atlanta and one in Russia, are authorized to store smallpox for research purposes.
"CDC, its administration partners, and law enforcement are investigating the matter and the vials' contents appear intact," CDC spokesperson Belsie González tells the AP in an email.
A similar discovery of smallpox vials was made in 2014 when an old Food and Drug Administration lab at the National Institutes of Health was being cleaned out. A spate of reports of other improperly stored or mishandled samples followed thereafter, including of ricin and Staphylococcal enterotoxin and of anthrax and influenza.