The Centers for Disease Control and Prevention is investigating the discovery of vials that are labeled “smallpox” in a laboratory in Pennsylvania, the health agency said Thursday.
The frozen vials “were accidentally discovered by a lab worker while cleaning a freezer in a facility that conducts vaccine research in Pennsylvania,” Belsie González, a spokeswoman for the CDC, said in an email Thursday.
She added that the CDC is working with police officers to investigate the vials. The agency said the vials appeared to be intact.
“The worker who discovered the vials was wearing gloves and a face mask,” she said. “There is no indication that anyone has been exposed to the small number of frozen vials. We will give further details when they become available.”
The CDC did not say where in Pennsylvania the vials were discovered or how many there were.
Mark O’Neill, press secretary of the Pennsylvania Department of Health, said there are “a small number of vials” found at a Merck facility in Montgomery County, outside Philadelphia.
Merck did not immediately respond to a request for comment on Thursday. The FBI referred investigations to the CDC
“The Pennsylvania Department of Health would like to emphasize that there is no known threat to public health and safety,” Mr. O’Neill said. “As referenced by the CDC, there is no indication that anyone was exposed to the small number of frozen vials that were labeled ‘smallpox.'”
Citing a report from the state health department, Kelly Cofrancisco, a spokeswoman for the Montgomery County Office of Communications, said there are a total of “15 questionable vials” with five labeled as “smallpox” and 10 as “vaccinia.”
Smallpox, an infectious disease caused by the smallpox virus, has caused giant outbreaks for centuries, with about three out of every 10 cases proving fatal, according to the CDC.
Symptoms include a very high fever and a blistering, progressive skin rash.
The virus claimed the lives of 300 million people in the 20th century, according to the World Health Organization.
In the event of an outbreak, the CDC said, “there is enough smallpox vaccine to vaccinate every person in the United States.”
The agency said the last natural outbreak of smallpox in the United States was in 1949. The last known natural case was in Somalia in 1977, according to the WHO.
The WHO said there are two authorized depots of smallpox virus supplies, with the CDC in Atlanta and at research center in Russia. That year, six vitriol vials that contained the smallpox virus were found in a warehouse in a government laboratory outside Washington. At the time, the CDC said there was no indication that lab workers or the public had been exposed to the content.
The CDC said smallpox research in the United States has focused on the development of vaccines, drugs and diagnostic tests to protect people from smallpox in the event that it is used for bioterrorism.
Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, said smallpox can be fatal “even after it’s freeze-dried.”
He said that due to its highly infectious nature, “the virus itself must be kept cold.” At room temperature after many years, he said, it was “unlikely that the virus would retain any ability to infect humans.”
Dr Glatter added that there has been an ongoing debate over whether governments should retain virus samples or remove all known copies of the virus.