A laboratory mistake at the federal Centers for Disease Control and Prevention in Atlanta this week has cast new light on safety problems at the agency.
The CDC announced late Wednesday that a lab technician may have been exposed to the deadly Ebola virus and is being monitored for signs of infection for 21 days, the incubation period for the disease.
Word of the error provoked concern and disbelief from some safety experts. Dangerous samples of anthrax and flu were similarly mishandled at the CDC just months ago, eroding confidence in an agency that has long been one of the most respected research centers in the world.
Other employees who entered the lab where the mistake occurred were being examined for possible exposure. There are fewer than a dozen, and so far it appears that none was infected, said Thomas Skinner, a CDC spokesman.
There is no risk to the public, officials said. CDC spokesman Barbara Reynolds said the lab was decontaminated twice and that the material was destroyed before CDC officials became aware of the mistake.
The possible exposure is under internal investigation and has been reported to Secretary of Health and Human Services Sylvia Burwell, Reynolds said.
Transfers from the lab where the experiment material came from have been stopped during the internal review, and the lab where the exposure may have happened is closed, Reynolds said.
The error occurred Monday when employees at a high-security lab working with Ebola virus from the epidemic in West Africa sent samples that should have contained killed virus to another CDC laboratory down the hall.
But the first lab sent the wrong samples -- ones that may have contained the live virus. The second lab was not equipped to handle live Ebola. The technician there who worked with the samples wore gloves and a gown but no face shield.
The mistake was discovered Tuesday, said Dr. Stuart Nichol, chief of the CDC's Viral Special Pathogens Branch. He ascribed it to human error.
In a statement, Dr. Tom Frieden, director of the CDC, said he was "troubled by this incident" and promised "a full review of every aspect." Thousands of agency scientists, he said, "have taken extraordinary steps in recent months to improve safety." The CDC promised last summer to improve its safety procedures and chose a panel of outside experts to advise it on how to do so.
Under questioning from members of Congress in July, Frieden admitted that errors at CDC labs were not isolated mishaps but rather part of a broad pattern of unsafe practices.
Richard Ebright, a molecular biologist at Rutgers University and an expert on biological weapons, said the errors were inexcusable. Labs that produce samples of killed virus should test to make sure they are dead, Ebright said, and labs receiving those samples should test them before working with them.
"CDC labs that receive putatively inactivated samples still are working with them with no safety and security precautions beyond those at a dentist's office," Ebright said.
Skinner, the CDC spokesman, said the procedures mentioned by Ebright were "very much in place" and that the agency would find out whether they had been followed.
Najmedin Meshkati, a professor of industrial and systems engineering at the University of Southern California and an expert on human error, said: "I am speechless. This is yet another indication that this organization needs to do a serious soul-searching to improve its safety culture."
The previous incidents occurred in the spring and summer. In June, CDC scientists sent anthrax samples, supposedly killed, to laboratories that were not equipped to handle dangerous pathogens. But the bacteria turned out to be live because a deactivating technique too weak to wipe out anthrax spores had been used. Dozens of employees were offered antibiotics and anthrax vaccine; none became infected.
The head of the laboratory that shipped the bacteria resigned a few weeks after the mistakes came to light. Although CDC officials gave no reason for his resignation and said it was voluntary, they had previously indicated that they feared workers in that laboratory had grown careless because of lax supervision.
In another blunder, a CDC lab accidentally contaminated a relatively benign flu sample with an H5N1 bird flu strain that can be fatal in humans, then shipped it to a lab at the Department of Agriculture. Scientists at the receiving lab detected the error, and no one was harmed.
Although that incident occurred in May, senior CDC officials were not told about it until July 7, and Frieden did not hear about it until two days after that. He said in an interview in July that he was "stunned and appalled" by the incident.
The mistakes led the CDC to appoint a panel of outside safety experts in July to advise Frieden on how to correct sloppy procedures. The CDC temporarily closed its flu and bioterrorism laboratories, and halted shipments of all infectious agents from its high-security labs until those labs could be cleared by a newly formed safety panel.
In August, the special pathogens branch -- where the Ebola accident occurred Monday -- received permission to send out infectious agents again.
Nichol said the high-security lab where the mistake occurred had prepared two sets of fluid samples from guinea pigs infected with Ebola. The fluid was handled as if it contained live virus, though it is not certain that the virus was present.
One set of samples was to remain in the high-security lab so researchers could try to isolate the virus from it. The other was to be treated with a solution that would kill the virus and then was sent to a lower-level laboratory where a technician would try to extract genetic material from it.
Somehow, the samples were switched: The ones with killed virus stayed in the high-security lab, and the ones that may have contained live virus were sent to the lower-level lab and processed there.
"We'll learn from this mistake as we've learned from the others," Reynolds said.
News of the technician's possible exposure to Ebola came days after Frieden returned from West Africa, where an outbreak of the virus has killed thousands. Frieden said Monday that response to the Ebola outbreak has improved significantly in recent months, but the virus continues to spread in Monrovia, Liberia and Conakry, Guinea.
Information for this article was contributed by Denise Grady and Donald G. McNeil Jr. of The New York Times; by Phillip Lucas of The Associated Press; and by Caroline Chen of Bloomberg News.
A Section on 12/26/2014