text: After potentially serious back-to-back laboratory accidents, federal health officials announced Friday that they had temporarily closed the flu and anthrax laboratories at the Centers for Disease Control and Prevention in Atlanta and halted shipments of all infectious agents from the agency’s highest-security labs.
  
  The accidents, and the C.D.C.’s emphatic response to them, could have important consequences for the many laboratories that store high-risk agents and the few that, even more controversially, specialize in making them more dangerous for research purposes.
  
  If the C.D.C. — which the agency’s director, Dr. Thomas Frieden, called “the reference laboratory to the world” — had multiple accidents that could, in theory, have killed both staff members and people outside, there will undoubtedly be calls for stricter controls on other university, military and private laboratories.
  
  In one episode last month, at least 62 C.D.C. employees may have been exposed to live anthrax bacteria after potentially infectious samples were sent to laboratories unequipped to handle them. Employees not wearing protective gear worked with bacteria that were supposed to have been killed but may not have been. All were offered a vaccine and antibiotics, and the agency said it believed no one was in danger.
  
  In a second accident, disclosed Friday, a C.D.C. lab accidentally contaminated a relatively benign flu sample with a dangerous H5N1 bird flu strain that has killed 386 people since 2003. Fortunately, a United States Agriculture Department laboratory realized that the strain was more dangerous than expected and alerted the C.D.C.
  
  In addition to those mistakes, Dr. Frieden also announced Friday that two of six vials of smallpox recently found stored in a National Institutes of Health laboratory since 1954 contained live virus capable of infecting people.
  
  All the samples will be destroyed as soon as the genomes of the virus in them can be sequenced. The N.I.H. will scour its freezers and storerooms for other dangerous material, he said.
  
  “These events revealed totally unacceptable behavior,” Dr. Frieden said. “They should never have happened. I’m upset, I’m angry, I’ve lost sleep over this, and I’m working on it until the issue is resolved.”
  
  The anthrax and flu labs will remain closed until new procedures are imposed, Dr. Frieden said. For the flu lab, that will be finished in time for vaccine preparation for next winter’s flu season, he said.
  
  Dr. William Schaffner, the head of preventive medicine at Vanderbilt University’s medical school, said he thought all American labs should stop shipping all hazardous agents until they have reviewed their safety procedures. Although there is no obvious way to force them to do that, he said, the federal grants that most labs depend on “could be the stick.”
  
  Dr. Frieden himself suggested that the accidents had implications for labs beyond his agency, arguing that the world needs to reduce to absolute minimums the number of labs handling dangerous agents, the number of staff members involved and the number of agents circulating.
  
  Scientists doing the most controversial work — efforts to make pathogens more lethal or more transmissible — say the research helps predict mutations that might arise in nature so that vaccines can be created. But other scientists feel that creating superstrains is unacceptably dangerous because lab accidents are more common than is often acknowledged, as Dr. Frieden’s announcement indicated.
  
  The revelations at the C.D.C. renewed calls for a moratorium by opponents of such “gain of function” research.
  
  “This has been a nonstop series of bombshells, and this news about contamination with H5N1 is just incredible,” said Peter Hale, founder of the Foundation for Vaccine Research, which lobbies for more funding for vaccines but opposes “gain of function” research. “You can have all the safety procedures in the world, but you can’t provide for human error.”
  
  At the C.D.C. itself, Dr. Frieden said, staff members who knowingly failed to follow procedures or who failed to report dangerous incidents will be disciplined. A committee of experts will be convened to revise procedures.
  
  In the flu-related incident, a C.D.C. lab accidentally contaminated a sample of less-dangerous H9N2 bird flu, which it was preparing for shipment to an Agriculture Department laboratory, with the H5N1 bird flu strain.
  
  Though the contamination was discovered on May 23, Dr. Frieden said that he was dismayed to discover that senior C.D.C. officials were not informed until July 7, and that he was told only 48 hours ago.
  
  Nonetheless, he said, “we have a high degree of confidence that no one was exposed.” The flu material was handled in high-biosafety-level labs in both agencies, and the workers wore breathing apparatuses.
  
  In theory, the flu-related accident could have been much worse than the anthrax one.
  
  Anthrax can kill those who inhale it, but is not normally transmitted between humans, so an infected laboratory worker presumably could not have gone home and passed it on. H5N1 bird flu has killed about 60 percent of those known to have caught it, almost always after contact with poultry. Although it does not easily jump from person to person, it is thought to have done so several times.
  
  The anthrax episode took place on June 5 in the agency’s bioterrorism rapid response lab as part of testing a new mass spectrometry method.
  
  The new C.D.C. report found several errors: A scientist used a dangerous anthrax strain when a safer one would have sufficed, had not read relevant studies and used an unapproved chemical killing method.
  
  The error was discovered by accident. The door to an autoclave that would have sterilized samples taken for safety tests was stuck, so they were left in an incubator for days longer than normal. Only then did a lab technician notice that bacteria believed to be dead were growing.
  
  Later tests done at the C.D.C. and at a Michigan State Health Department lab as part of the investigation confirmed that the chemical method would have killed any live, growing anthrax in the samples that were sent out, but might not have killed all spores, which are surrounded by a hard shell and can also be lethal.
  
  Although anthrax terrifies laymen, “when you work with it day in and day out, you can get a little careless,” Dr. Frieden said. “The culture of safety needs to improve at some C.D.C. laboratories.”
  
  A version of this article appears in print on July 12, 2014, on page A1 of the New York edition with the headline: C.D.C. Shuts Labs After Accidents With Pathogens. Order Reprints|Today's Paper|Subscribe
summary: After potentially serious accidents involving bird flu and live anthrax, the Centers for Disease Control and Prevention shut the Atlanta labs and halted shipments of infectious agents.