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Human skin infected with the smallpox virus.

Human skin infected with the smallpox virus.

U.S. Centers for Disease Control and Prevention

Six vials of smallpox discovered in U.S. lab

Federal scientists last week discovered a half-dozen forgotten vials of smallpox virus while cleaning out a storage area on the campus of the National Institutes of Health (NIH) in Bethesda, Maryland. Variola, or smallpox, which killed hundreds of millions before it was declared eradicated in 1980 through a worldwide vaccination campaign, is legally stored at only two locations in the United States and Russia.

The six vials of freeze-dried virus, apparently dating from the 1950s, were found by a scientist from the Food and Drug Administration (FDA) on 1 July in a cold storage room that was originally part of an NIH laboratory, but was transferred to FDA in the early 1970s. The FDA laboratory is being moved to the FDA’s main campus, according to ABC News, NBC Washington, and a statement today from the Centers for Disease Control and Prevention (CDC). The vials were labeled as containing variola and were packed in a cardboard box along with 10 other vials with unclear labels, ABC News reports.

NIH immediately placed the vials in a high-security containment laboratory in Bethesda and notified CDC of the discovery. Yesterday, a three-person CDC team flew the samples by government plane to Atlanta and transferred them to CDC’s biosafety level 4 lab, where testing overnight revealed that the six labeled as variola virus were positive for variola DNA. More tests will reveal whether the virus can grow in culture, CDC says.

The vials will then be destroyed, and if they contain viable virus the World Health Organization (WHO) will be invited to oversee the destruction. CDC’s Division of Select Agents and Toxins is working with the FBI to investigate the origin of the samples. Smallpox is regulated as a select agent under U.S. laws that require special safety and security practices.

Most Americans born since 1972 have not been vaccinated for smallpox. Under a 1979 WHO agreement, the only remaining official live smallpox stocks are kept at CDC in Atlanta and the VECTOR laboratory in Novosibirsk, Russia. Every few years, WHO considers whether these last stocks should be destroyed. At a meeting in May, WHO members again postponed a decision because some experts argued that the stocks are still needed for research.

This is not the first time smallpox vials have been discovered unexpectedly in a laboratory. According to this 2009 article by the late bioweapons researcher Jonathan Tucker, after most smallpox stocks were shifted to the two central repositories, “[a] few scientific research centers also reported finding and destroying vials containing the smallpox virus that had been retained inadvertently in laboratory freezers, sparking fears that other poorly secured samples might exist that could fall into the hands of terrorists.”

This past December, WHO’s smallpox advisory committee reported that the organization was “finalizing arrangements for the destruction of cloned variola virus DNA fragments that have been stored in South Africa.” It is not clear whether the fragments, which can be used for vaccine development, represented a serious safety threat. Their destruction reportedly occurred this past January under WHO’s supervision.

In an earlier incident, forgotten smallpox samples were found in a lab in an Eastern European country in the 1990s, former WHO official David Heymann told NBC Washington. Thomas Inglesby, director of the Center for Health Security at the University of Pittsburgh Medical Center in Pennsylvania, wrote in an e-mail to ScienceInsider that he is not aware of any other such discoveries: “My colleagues and I … can’t recall other times with finds like this. … Not to say it hasn’t happened, but nothing that we know of.”